Dynaco SCA 80Q Stereo Amplifier Instruction manual

SERIAL NUMBER This number must be men- honed in all communications concerning this equipment. INSTRUCTIONS FOR ASSEMBLY OPERATION ТИТ = Гаги В ТД! оо kt LL ВОНИ CONTENTS Operating mitriuctions rr Ta aT A A, ЕН 1 Schematic Diagram series brn aE EE Ew = 16 installing your SCA-BOO 2.25 00u rs iuanen paume ee ns ñ In Care ol DIN ==... .......—. A ent Optional Connections +...-::==... a e 6 Service and Warranty INfOMmAalON 220004000000 e... 3) Listening to Dynaquad Sound... ia icici naa 7 PERS LEY Cedo ade 8 Bad po APE CE EE Technical Information +......0000 ss. ner. Ehen В Alternate AC Line Connectidas .es--e....raesnacace 8 Assembly Instructions or cree rm ans sns sass aaa 9 Pictorial Diagram -.-.—...e=0scdatenmecindda red: NET SPECIFICATIONS POWER OUTPUT RATING: Less than (155% total harmonie dis OUTPUTS: Front or Main Speakers: 4 to 16 ohms. tortion at any power level up to 30 watts continuous average Rear Speakers: 8 ohms, or as Remote: B or 16 ohms, power per СП"! АА #5 ohms al ar frequency behacen Front panel headphones: al ohms OF higher, 0 Hz and 20 kHz with bath channels driven, with FIL pre Tape output: 600 ohms from phono input conditioning. Distorlion decreases at lower power levels (same as source on high level inputs). TONE CONTROL RANGE: +12 db at 50 Hz and 10 kHz CONTROLS: Selector Switch, Volume, Balance, Bass, Treble, Tape Monitor Switch, Loudness Compensation Switch, Filter Switch, Sterco-Mono-Blend Switch, Speaker Switch, Power Switch, FREQUENCY RESPONSE: {at 1 watt output into 8 olvms) SEMICONDUCTOR COMPLEMENT: 20 trandi£tors; 10 diodes. High level inputs: 20.5 dE trom 15 Hz to 50 kHz DAMPING FACTOR: Greater than 40 from 20 Hz to 10 kHz. Phono input: 20.5 dE of RIAA equalization SEPARATION: 65 db by IHF standard standards; NOISE: High level inputs: 80 db below rated output, ; Hy 4 Phono input: More than 60 db below rated output, = ob ra = > i010. He ; | | SIZE AND WEIGHT: 13/37 x 4/4" x 10" deep. INFUTS: RIAA magnetic phono: 47,000 ohms; 3 mv. 16 pounds (7.2 kg). Special low level: (2nd phonol: 47,000 ohms; 3 mv, High level: {radio tuner, tape amp, sparel: POWER CONSUMPTION: 750 watts maximum; 35 walls quics- 100.000 ohms: 0.13 volt. cent: 59/60 Hz @& 100, 120, 220, or 240 volts AC INTERMODULATION DISTORTION: Less than 01% at any level up lo rated power into 8 ohms wilh any combination ol tesi frequencies. Distortion decreases at lower power levels 100 Hz 1 kHz 10 kHz SQUARE WAVE PERFORMANCE: This is a good indication of linearity from 10 Hz to 100 kHz, since good square wave reproduction requires bandwidth in excess of 1/10th to 10 times displayed frequency. 4 | — ; — TL +10 DN 0 db Ч ~ =10 - LL + | = 20 50 100 Hz 1000 20000 LOW POWER FREEDOM FROM DISTORTION: at 1/10th TONE CONTROL RANCE watt, a 20 kHz sine wave (the most difficult audio frequency) Narrow band filter characteristic shown as broken line, shows absolutely no signs of crossover or natch distortion. 2 THE DYNACO SCA-50Q Do not attempt to install or use this amplifier until the section “Operating Instructions” has been carefully read, The Dynaco SCA-BOQ is an all silicon solid state stereo control amplifier of exceptionally high quality. It functions as the control center for all mono or stereo signal sources, such as a record player, radio tuner, tape recorder, television sound, ete, and provides output connections from two 30 watt power amplifiers for either two or four loudspeakers, as well as a front panel jack for stereo headphones. Thoughtful planning has provided exceptional flexibility with remarkable ease of operation. The SCA-800 incorporates special circuitry which enables Dynaquad"* 4-dimensional playback for increased realism from a four speaker system without any additional electronics. Alternatively it may be used as a conventional two channel stereo amplifier with provision for optional connection of a second pair of speakers in a remote location, The SCA-800Q has been designed to be used under normal conditions without special safety precautions, just as if it were a high grade tube amplifier. There are no circuit breakers, speaker fuses, or other resettable devices to impede the use of the SCA-80Q under any reasonable conditions of use or abuse. This is achieved by using novel circuits (on which patents are pending) which automatically and instantly protect the amplifier. The components in the SCA-800 are of the highest quality to protect against failure, both now and for many years in the future. The transistors have been selected for minimum noise and distortion in sustained use. All parts are used conservatively with close tolerances to assure proper operation, and all four etched circuit modules in the kit have been pretested under actual use conditions to ensure that every unit, after assembly, will meet the specifications normally associated with laboratory prototypes, The specifications of the SCA-800) speak for themselves. The distortion at low levels is comparable to that of the finest tube designs, while the high power distortion remains inaudible. Specifications do not reveal all the facets of sound quality, however, In use with varying program material, the SCA-B0G) justifies its design efforts to have quali- ties of ease and naturalness alwavs sought and rarely achieved in solid state designs. There is no extra bright- ness or stridency which is unfortunately sometimes attributed to high fidelity sound, but rather there is an impression of limitless range and effortless handling of the highest power peaks, Like any precision equipment, the superior capabilities of the SCA-BOQ will best be realized when it is properly connected and operated. Therefore, read these instructions, and make the specified connections to the input audio source and to the loudspeakers before connecting the amplifier to a source of AC power. OPERATING INSTRUCTIONS Connection from Phonograph The pair of input sockets marked Phono provide RIAA equalization for magnetic phonograph cartridges. They may be used with all normal magnetic cartridges having maximum inputs up to 80 millivolts and designed for a load impedance of 47,000 ohms. The upper row of input connections is intended for the feff channel. Special Input This input provides a second low level option which is normally wired for a second magnetic cartridge with RIAA phonograph equalization, enabling the connection of two record players—a turntable and a record changer, for example. Other connections are possible with internal wiring changes, as described in the section “Optional Con- nections” later in this manual. Ground Connection Some record players or tape machines have an extra wire which is to be attached to the preamplifier chassis. A grounding screw Gnd is provided for this purpose. Under some unusual conditions of use, where it is advisable to ground the system to a water pipe or similar earth connection, this screw can serve as the connection point. In general, it is advisable to use the minimum number of separate ground leads necessary to achieve lowest hum. Some experimentation may be necessary, but extra leads often cause an increase In the hum level of the system. Connection from Radio Tuner and other High Level Sources The Tuner and Spare inputs are identical and receive flat high level signals from AM/FM/Multiplex radio tuners, additional tape recorders, audio signals from a TV set, étc., via regular shielded cables. Connection from Tape Recorder Most tape machines available today include playback preamplifiers. The cables from their “preamp output” or “line output” sockets should be connected to the Tape Amp inputs, and the selector switch turned to Tape on the SCA-800. This input can also be selected by the Monitor switch, as described later. If you have a tape deck which does not contain playback electronics, it is possible to add the necessary equalization components to enable such playback through the Special input. See “Optional Connections” later in this manual. Connection to Tape Recorder If your tape machine has recording facilities, audio cables should be connected from the Tape Out sockets on the SCA-80Q to the “radio,” “high level” or “line” inputs on the recorder. The recorder inputs should require signal levels nominally between 100 millivolts and one-half volt for full recording level. Microphone inputs on a recorder are not suitable because their sensitivity is too high. Tape Out connections are made in the SCA-80Q ahead of all controls except the selector switch so that these controls may be operated to adjust the amplifier signal to the speakers during the recording process without affecting the signal going to the tape recorder. These outputs are at the same level and impedance as the source for all high level inputs, and are low impedance outputs from the phono preamplifier stages. They are ahead of the Mode switch too, so each output is independent. They should not be externally connected together with a Y adapter for monophonic recording from a stereo source. If vou wish to record monophonically from a siereo phono cartridge, it will be necessary to parallel the outputs of the cartridge itself in accordance with the manu- facturer’s instructions. Then one audio cable from either 3 (but not both? Tape Out socket may be connected to the single input on the recorder. If extensive mono recording from stereo phono sources 18 likely, see “Optional Con- nections” in this manual. Mono recordings from high level sources such as a tuner present noe problems because the tuner output can be switched to mono. The SCA-800 does not provide the equalization and bias requirements of a complete tape recording preamplifier. It therefore cannot be used as such. Connection to Loudspeakers The SCA-80) 18 provided with four pairs of black and gold output terminals, each indicated by a loudspeaker symbol. If one pair of speakers 15 used for conventional two-channel stereo, connect them to the top row of terminals. A second pair of speakers located in the same room enables the benefits of Dynaguad™ 4-dimensional reproduction. These rear speakers are connected to the bottom row of output terminals. 8, +, red nn В. +, red 5 ; x Cc, —, E“ | С, —, Маск = FRONT SPEAKERS = CF > E = Er a REAR SPEAKERS 5 | Le 9 © 9, | =||z E 3" ве В \ |+ + Y Il” “js | = If you prefer to use the second pair of speakers in a remote location, so that conventional two-channel stereo is heard in both rooms, the remote speakers are connected to the bottom row of output terminals, and in additton a short piece of wire (jumper) must be connected from the top left common terminal to the bottom left commen terminal, Each speaker is connected to a black or common terminal and to the adjacent gold or five terminal. The black terminals are connected together internally, so you can use other equipment which requires common output grounds. You must be certain that the polarity of such outpui con nections is never reversed, and that the live sides are never accidentally connected together in accessory equipment, + "Spade lugs” are provided for attaching to the speaker wires to assure a good connection to the terminals. These can be simply crimped over the bared end of the wire, but if a soldering iron is available, soldering them on will make a more secure connection. If stranded wire (as with lamp cord) is used, the wire strands should first be twisted together or “tinned” with solder to avoid fraying. Make certain that no wire strands are able to touch another terminal or the chassis before vou turn the amplifier on. | The front speakers may be 4, 8 or 16 ohms rated impedance. The rear speakers of a 4-D system should be 6 ohms; they should be identical models; they should have very uniform impedance characteristics; and their efficiency and sonic characteristics should be similar to those of the front speakers. If the rear speakers are 16 ohms, the 10 ohm resistor inside the back panel should be replaced with a 200 ohm, 10 watt unit. Tf the second pair of speakers is connected for remote use, they may be either 8 or 16 ohm impedance. Only one speaker should be connected to each pair of terminals. For speaker cables of less than 50 feet, ordinary #18 lamp cord may be used. For longer distances it is suggested that heavier cable (#16 or 414) be used. The terminals on loudspeakers are marked in different wavs, and sometimes are not identified, Corresponding terminals may be marked (+), (8 ohms), (1) orin red. Itis important that the “sense” of the wiring to each speaker be consistent, so that all speakers will be connected in phase. With lamp cord this is easy because one lead is coded—usually either with a tracer thread wound around one of the wires, or with à slight molded ridge on the outer plastic insulation of one conductor, or with different color conductors. Two speakers are connected in phase when maximum low frequency output is heard when they are driven from a monophonic source, Lowered output is observed when the connection to one of the speakers is reversed (out of phase, or reversed polarity), This is most apparent when the speakers are connected to the same amplifier channel, and are placed side by side, or facing each other a short distance apart for test purposes, In a 4-D system, each of the speakers should be compared in turn with the original if there 18 any doubt of their phasing. Speakers which require electrical equalization (through the Tape Amp monitor input and the Tape Output) may be used in a 4-D system only if all speakers require the same equalizing networks in the amplifier stages. It is not feasible to mix equalized speakers with conventional speakers connected to the same amplifier, The nominal power rating of the SCA-800 is based on a load impedance of 8 ohms. Loudspeakers with impedances of 4 or 16 ohms may also be used, with some reduction of the maximum power capability at some frequencies. With a 16 ohm speaker load, maximum power can be expected to be about 26 watts per channel. A more detailed explana- tion of amplifier power output characteristics is available on request from Dynaco. Selector Switch This rotary switch selects your choice of program source in both channels simultaneously. It also enables vou to select playback from a tape recorder, differing from the more common arrangement which requires that vou operate a separate Monitor switch to select the recorder. The SCA-BOG also provides a Monitor switch (described later), but selection of the recorder for routine playback is made in the same way as all other inputs to avoid confusion. Volume Control The output level of both channels is adjusted simultaneously by this control, with close tracking of the two stereo channels so that the program material will remain in balance over most of its range. This control has been designed to provide a slow increase in volume over the first half of its rotation, and a more rapid volume increase above 12 o'clock. This enables most satisfactory operation with both high efficiency and low efficiency speakers, and with both high and low output phono cartridges. The relative position of the volume control on different pieces of equipment 15 not an accurate indication of the power output, because 1t is affected by input levels and speaker efficiency. Balance Control The balance control is normally centered for equal signals in both channels. Rotation to the right shifts the sound source to the right by reducing the left channel level, and conversely. This control has a very gradual change for the first 90° either side of center to facilitate delicate adjustments, but one channel is silenced at either extreme of rotation. A conventional two speaker stereo system requires a balance control to correct for differing speaker efficiencies, or inequities in room energy distribution, as well as oeca- sional program variations. A 4-dimensional system utilizes the balance control to achieve precise electrical symmetry in the system, and thus to attain maximum separation. With a 4-D system the balance control is no longer used for shifting left-to-right emphasis, The listener is advised to shift his position to adjust for such inequities. Tone Controls The special design of the separate bass and treble tone controls 18 a patented Dynaco arrangement which assures that the tone controls are “out of the circuit” when they are centered. This provides the perfectionist’s performance goal with the convenience of continuously variable correction without the complication of extraneous disabling switches, The normal or “flat” position 15 centered, with Incréas- ing effect to the right, and decrease to the left. Tone controls alter the original signal to suit the user; but these alterations are deviations from truly accurate reproduction. The reference point should alwavs be the center, which gives no frequency discrimination. The tone controls also help to correct for record compensation characteristics of older discs which do not follow the present RIAA standard plavback curve. Monitor Switch This switch enables direct comparison of the source signal indicated by the selector switch, with the same signal played back from a separate playback amplifier of a tape recorder. This feature is applicable when recording through the SCA-900 to a tape recorder which has separate playback preamplifiers and three or more heads designed for simultanecus playback while recording. For example, while recording from a radio tuner, the selector switch is turned to Tuner, and Tape Out is connected to the recorder input. The playback output of the recorder is connected to Tape Amp. You will hear the tuner directly when the Monitor switch is in its normal position, marked Input. When the Monitor switch is on Tape you will hear the program a fraction of a second after it has been recorded, now being played back from the tape. For this, the tape recorders own monitor switch must be left in the tape, compare, playback or monitor position. You must remember to keep the Monitor switch on Input normally, or vou will get no signal from any of the other program sources selected by the selector switch. The Monitor switch serves no purpose when the Selector Switch is turned to Tape. Loudness Switch The Loudness switch is normally left off, but it may be used at lower settings of the volume control to provide an increase in bass to compensate for the ear's lack of sensitivity to low frequencies at low sound levels. 'The high fidelity purist usually avoids any such compensation; but many listeners will find this switch, used in modera- tion, adds listening enjoyment at low levels. This sonic correction does not add boom or muddiness to the reproduction. Filter Switch With good program material the filter switch will be left m the flat position, or effectively out of the circuit. The rumble setting provides attenuation below 100 Hz, mini- mizing low frequency disturbances. The narrow band position rolls off both high and low frequencies simultaneously. It thus makes listening to poorer program material more enjoyable since it does not shift the original tonal balance. High frequencies are attenuated above 6 kHz. Mode Switch This switch will normally be left in the stereo position with stereo program material, providing full separation of the two channels. The blend position reduces the normal stereo separation to 6 db, as for example when the two speakers are spread too far apart for realistic reproduction of a solo instrument, When using headphones, this position frequently provides more realism by reducing the excessive sonic spread. The mono position parallels the two channels, and is the proper position for listening to monophonic records plaved by a stereo cartridge, as it eliminates the vertical noize components of the signal. When listening to a monophonic radio broadcast with some tuners, too, some improvement may be noted in this position. If a monophonic source, such as TV sound, is connected to one channel input, this signal will be available through both speaker channels when this switch is in the mono position. Speakers Switch The Front position of this switch plays through only the pair of speakers connected to the upper terminal strip. The Four (middle) position connects all speakers, either in the normal 4-D arrangement, or as equivalent-signal Main and Hemote pairs when the connecting wire jumper ls installed on the back panel as indicated there. The spring-return Null position is used for balancing the 4-D system. First play the program at the normal volume setting, and then while you hold the switch against the spring, adjust the Balance control slowly for a precise null (no sound). Then release the switch, and vou will have 4-D sound. Occasionally, differing program sources or changes in thé volume control setting make it advisable to rebalance for best 4-1) results. Headphone Output A standard 3-circuit phone plug fits this output, wired so that the tip connection is the left channel. Series resistors attenuate the power amplifier output, and headphones of 4 ohms or higher impedance may be used. When headphones are connected, all speaker outputs are automatically silenced. You should not have headphones connected when the Speakers switch is in the Null position. Power Switch This switch has the obvious function of turning the SCA-800 on and off, and contains an integral pilot light. It also switches whatever is connected to the lower (switched ) AC outlet on the back panel, such as a radio tuner. The top AC back panel outlet, which is always or, is used for a record plaver or tape recorder. Their drive mechanisms cannot then be damaged if the amplifier power ls turned off without disengaging the machine. INSTALLING YOUR SCA-500) The SCA-B00 generates some heat in normal use—mostly from the power supply resistors—so adequate ventilation must be provided to ensure long trouble-free life. As with anv transistorized amplifiers, higher power outputs increase the heat output proportionately, so you must never limit the air flow through and around the SCA-80G. Do not set anything on top of the perforated cover, Vertical (face up) mounting is not encouraged, since the heat dissipation is not as effective as in the normal horizontal placement. If the unit must be mounted face up, a fan 18 recommended, and some provision for supporting the weight of the power transformer should be made to avoid distorting the front panel. H the SCA-800 is inadvertently left on for a lengthy period of time, no problems will be encountered, for the transistors remain cool except under high signal conditions. With sustained high power output, it is normal for the bottom to get much warmer than the cover, for the heat sinks dissipate heat through the chassis. As with all solid state amplifiers, maximum heat is generated at about half the maximum power output. At full power output from both channels a transistorized amplifier must dissipate as much heat as an equivalently powered tube amplifier. At full power, the SCA-800 puts out as much heat as a 250 watt light bulb. Panel mounting requires a single rectangular cutout 1946" by 314s", The rubber feet are removed for such use. You can simply provide a shelf flush with the bottom of the opening. Be sure to cut out the shelf in the area of the ventilation slots on the chassis, Or, an accessory PBK bracket kit is available from Dynaco for $2 postpaid. No COD's please. The brackets take the place of the shelf, and can accommodate panel thicknesses up to one inch. Instructions accompany the kit. but note that the hole for one of the mounting bolts is located underneath CTL, and this bolt will be secured only by the wing nut provided with the kit. Be gure that CTL is properly clamped flush to the chassis after the bolt is installed. Cautions to be observed The SCA-800) contains circuits which will provide nearly complete protection against abuse (including the cautions noted below), but you should not challenge fate. We all 6 know that parachutes are quite safe—but why jump to test one? The need for protective circuitry in solid state equipment is a direct result of its inherent susceptibility to failure compared with the ruggedness of vacuum tube equipment. You will avoid possible damage to costly transistors and other components if vou follow these few simple rules: 1. Do not connect or disconnect inputs or outputs when the amplifier power is on. 2. If vou hear any abnormal noises, turn off the equipment and locate and eliminate the source of the noises hefore using the SCA-80Q, These noises may result from partially connected audio cables or similar faults not connected with the SCA-80GQ, but they can be signals or symptoms of signals of excessive amplitude. 3. Do not operate a tape recorder in the fast wind or rewind mode when the volume control is advanced, as this could produce large signals at inaudible frequencies, 4. Avoid any output connection system which risks directly connecting the “live” side of one channel to the “live” side (gold terminal) of the other channel when stereo (different) signals are involved, This is not likely in any properly wired system or accessory, but an accidental change of polarity in the connections to a system requir- ing common ground connections could be costly. Of particular note: headphone junction boxes. 5. Avoid shorting together the two wires to a loudspeaker, and do not use any switches in the output of the shorting type. Be sure that no strands of connecting wires are free Lo touch anything except the intended terminal, 6. Do not operate the amplifier if excessive temperature rise is noted. OPTIONAL CONNECTIONS The design of the SCA-80Q makes it easy to “customize” in several ways to suit individual needs, A supplementary dala sheet is available on request from Dynaco which outlines the necessary changes to provide the following variations. The normal wiring of the selector switch provides HIAA equalization for a second magnetic phono cartridge on the Special input. Other equalization can be provided, so that the Special input can accommodate either direct playback from a tape head, or a microphone, provided that the input load impedance remains at 47,000 ohms. To enable the Special position on the selector switch to be used as a second equalization position for the one phono input, the switch has been designed so that the phono input is not shorted when in the Special position. By installing appropriate components on the preamplifier circuit board and connecting a jumper on the back panel from the phono input to the special input socket, a second equalization position is available, If vou wish to tape record monophonically from stereo records, the Special input can be wired =o that it parallels the two phono inputs and provides a monophonic signal at the tape output jack. If vou wish to reduce thé sensitivity of the Phono input by 6 db, alternative wiring of the equalization components 15 included in the above data sheet. If headphones are chosen which require either more or less output level, appropriate value resistors can replace the 120 ohms resistors on the headphone jack. LISTENING TO DYNAQUAD SOUND When a monophonic music system is changed to two channel stereo reproduction the broadéned sound source and added “liveness” is apparent, Part of this enhance- ment 15 in the directional characteristics, but much is the result of an improved spatial sense, which 1s more subtle, Dynaquad 4-D sound provides both added front-to-rear directionality and marked improvement in recreating the ambience or “hall sound” of the original location. The apparent direction of each sound source is a function of the phase and amplitude relationships of its direct and reflected signals. À two-speaker stereo system 18 incapable of reproducing all of these signal combinations. The added back speakers in the Dynaguad circuit uncover substantial additional recorded material in normal two channel sources, heretofore hidden, by reproducing ail of these interrelated signals. We have long recognized that a soloist appears to be centrally located between the left and right speakers when this signal 18 recorded equally on both channels. The Dynaquad technique includes à simple method for intro ducing rear information in a complementary fashion, and a way to reduce the front signals when the two channels are reproduced through the back speakers. This enhances the proportion of rear and reflected sound information in the back speakers, and thus adds front-to-back directionality as well as ambience to the reproduction. The listener should be centrally located in the rear 14 of the room as the general level of the back speakers is 6 db lower than the front speakers, The back speakers will face the: listener from behind, usually are widely separated, and if possible, are best located above ear level, Although lower cost limited range speakers can be used in back, irregular response from poor speakers will cloud the capabilities of the main speakers, and weaken the reproducing chain. The back information includes signal components in the full audio spectrum. The lowest bass frequently contributes the most in added ambience—lhoôse characteristics which define the acoustics of the recording hall. The higher frequencies provide localization. As new recordings include specific rear sources, proper reproduction dictates comparable quality speakers in that sector. The depres of increased realism which the Dynaguad system provides over conventional two channel stereo will vary with the program material. With existing two-channel material the benefits you will derive are largely random and will depend on the particular recording techniques em- ployed. However, such benefits are dramatic on many recordings, and it is a rare performance which does not show some improvement. From your current recorded library select material which was recorded “live” with an audience, as well as recordings made in halls particularly noted for their fine acoustics. Among the pop material, look for selections which employ special sonic effects, too. Works which employ sizeable choral ensembles are also good candidates for 4-dimensional benefits, as well as material noted for unusually wide stereo separation. Begin by plaving the selection with the Speakers switch in the Front position, and then switch to 4-1). Audience participation, including applause, will surround vou, rather than appearing in front of vou. In pop material, vou may even find certain instrumentalists coming from behind you —the result of unintentional microphone misphasing. Organ works will frequently reveal added low end power. On many classical recordings, the initial impression when switching from two to four dimensions may not seem so dramatic, but after extended listening in 4-D, conventional playback will seem dry and lifeless by comparison. It is not uncommon to find that the transition from 4-D back to normal stereo loses more realism than the switch from stereo To mono. The benefits of 4-dimensional sound will often be most apparent in smaller rooms, where space restrictions were previously a significant handicap in reproducing really deep bass, or in creating any sense of “hall sound”, You should not expect (or want) to hear four separate and distinct channels, as this would be in essence 4-channel monophonic sound. Realistic musical reproduction implies a relationship between all sound channels and significant overlap, or commonality between them. The Dynaguad avstem takes advantage of this principle to develop the full reproduction potential of the two sound channels and of their phase and amplitude interrelationships. In effect, more information has always been on the record or tape than has been previously reproduced, ever since stereo recordings began. Recording engineers have long striven to find microphone pickup techniques and performer placement in the studio or hall which could uncover more of the “flavor” of the live performance on playback. What no one realized until now was that the prime restriction lay in the basic concept of stereo playback as a two-speaker environment, rather than in the lesser limitations of a dual-channel transmission medium. The Dynaquad system provides normal stereo reproduction from the front speakers. If vou switch off the back speakers, you will hear the same left-to-right separation vou always had. If a soloist was recorded in a central location, blended into the two channels, the solo will come from a virtual front center location between the front speakers. A monophonic program played through the Dynaquad system will likewise appear as a centered front source. Normal Dynaquad program reproduction (in the absence of a specific back signal source) will provide somewhat lower signal levels from the back speakers. This assures that in the usual listening environment, where the listener sits nearer the back speakers, proper placement of instru- ments or voices will be retained on the sound stage in front of you, Since the back speakers are closer, and form a wider listening angle, the fact that each back speaker reproduces some of the left or right channel information, in addition to the reflected sounds from the rear, provides the more sharply defined differences in intensity which preserve maximum directionality. In effect, the ear senses greater effective aural separation than the electrical signals apparently provide. The 4-dimensional effects are achieved because the information mn front and rear speakers is different —not because there 15 some front information appearing with reduced level in the rear. The added back speakers make it possible for the ear to perceive new signal information which contributes to realism, but which has previously gone unnoticed. Four dimensional sound cannot improve poor recordings or inadequate equipment. The better the reproducing system, the more it may show up any shortcomings. As one example, the proper azimuth alignment of tape heads is essential to full recovery of 4-dimensional information. As the quality of a music system's components goes up, so do the benefits of 4-D sound. TECHNICAL INFORMATION CIRCUIT DESCRIPTION The SCA-800) hag a number of unique circuit features on which there are patent applications. They contribute to the amplifier's exceptionally low distortion, long term reliability, resistance to abuse, and to its remarkable degree of reproducibility which marks a truly successful design. Those not interested in the technology may omit this section. A more detailed technical description for servicing will be found in a later section of this manual. Each preamplifier channel of the SCA-800 uses two pairs of npn transistors in similar configurations. On each circuit board the first pair is the low level preamplifier for the Phono and Special inputs, The input transistors are selected low noise types. The phono input can handle signals up to 100 millivolts without overload, The other pair of preamplifier transistors comprises the tone control stage. They operate at the higher signal levels of tuners, tape recorders, etc, as well as from the output of the phono preamplifier stage. The two sections of the preamplifier are interconnected by the selector switch, and all other controls and switches are located after the low level circuitry. Each pair of transistors has a DC feedback loop to stabilize operating conditions, as well as an AC feedback loop to provide optimum audio performance. The operating parameters of each stage have been critically adjusted to achieve the lowest possible distortion levels. The special feedback tone control system of the SCA-S0G ls an exclusive Dynaco development which provides continuous adjustment of the frequency extremes while providing a specific "center-flat” setting, When the controls are set to the normal mid-point of rotation, they are ellec- tively out of the circuit and have no effect whatsoever on performance. This is accomplished by special Dynaco- designed potentiometers. When the fone controls are operated away from the “flat” center point, the frequency response is varied by changes in the amount of feedback at the frequency extremes. The amplifier portion of the SCA-800Q includes unique circuitry to provide an unusual amount of protection while delivering exceptional performance. Transistors (1 and 2 are a direct-coupled feedback pair providing a high degree of stability and great linearity. This pair drives the power section, 3 through Q6, which are directcoupled and include IMC feedback stabilization. These four transistors act as a push-pull power transformer in that they do not have voltage pain, but they transform the signal from high impedance to low impedance. All transistors in the driver and power sections are included in one overall feedback loop. The amplifiers are designed to reduce—not just limit— the current through the output stage when there is any tendency to exceed a reference limit as a result of excessive drive signals or heavy loads. This protects both the load ( the loudspeaker) and the source (the output transistors). In the SCA-80Q the output transistors are operated without quiescent curren! and without the consequent heat rise caused by the bias current, eliminating the need for temperature compensaling devices. However, the SCA-800) does not exhibil any signs of the “Class B notch” commonly attributed to a lack of bias current. The output signal is taken from the junction of Q5 and 6 through coupling capacitor C7, which prevents DC from B reaching the speaker. An output capacitor large enough lo assure unrestricted low frequency response was chosen instead of the conventional and less costly plus-minus output circuit, It eliminates any need for balance adjustments or matching of components, and assures speaker protection in the event of output transistor failure, All of the large capacitors used in the SCA-80Q are special high-purity “computer grade” electrolytics chosen for maximum reliability. The output capacitors also serve as convenient forms for small value air-core chokes in the output which, in conjunction with an R-C circuit, roll off the response in the RF region (above 500,000 Hz), redue- ing interference and affording absolute stability under all circuit conditions. PERFORMANCE TESTS Special care must be taken when subjecting transistorized amplifiers to laboratory tests. Solid state circuits draw much more current at the frequency extremes than in the mid-band, and tests with other than the 8 ohm load for which the amplifier is designed may also draw higher current. High current raises transistor temperatures, causing increased current demand, so tests must be performed quickly under these conditions to avoid the action of the protective cut-back circuits which limit the current in the SCA-800) for safety reasons. The action of the protective circuitry may vield erroneous results, such as a notably lower apparent power output for rated distortion. High power measurements should first be “set up” with a low input signal, and then raised to a previously determined level for a quick reading. The extended power and frequency response of the SCA-800 requires thal even low power tests above and below the audible range be made quickly to avoid protective cut-back, This limits the duration of high frequency square wave tests, for example, Prolonged tests at high power levels, at the frequency extremes, or with abnormal load impedances require adequate thermal recovery time. Without it, the transistors are rendered more susceptible to subsequent overload, and the safely margin afforded by the protective circuils is sharply recluced. Callous disregard of these effects may result in eventual failure, for there is no such thing as absolute protection against deliberate abuse, Some of the heat generated is dissipated through the heat sinks to the chassis, so the bottom of the amplifier will get quite hot during tests. The maximum dissipation in transistorized circuits occurs at about half power. The line fuse in the SCA-800 has been chosen to provide maximum protection while allowing short duration currents in excess of its rating. The current demand for both channels operating at full power steady-state at 20 kHz (the severest test), for example, will slightly exceed the fuse rating, bul the slo-blo fuse will handle this for several seconds. When making full power tests at the frequency extremes, il is important that the line voltage be corrected for power line drop because of the high current demand. The capability of the supply will be limited by excessive line losses, and the indicated distortion may nse at maximum power when both sides are driven simultaneously. ASSEMBLY INSTRUCTIONS GENERAL INFORMATION Assembly of the SCA-800 is exceptionally simple when compared to other kits. The preassembled etched circuit boards have saved vou much of the work, and the assembly that remains is arranged in an open, uncluttered layout that makes wiring quick and easy. The construction time will be only a few hours, but it is best to work slowly and carefully rather than worry about the time. Construction will be greatly simplified if you have someone help vou by reading the steps aloud, selecting the required parts, and preparing the necessary wire lengths as you pr When you unpack your kit, check off the components against the parts list at the back of the manual. You can identify unfamiliar parts by matehing them to the pictorial diagram or photograph. Have the proper tools at hand before starting assembly. You will need a pencil-type soldering iron of 30- to 60-watt rating with a small tip, long nosed pliers, diagonal cutting pliers, a medium-sized screwdriver, and 60/40 rosin core solder not larger than Ma” diameter. You will also find a damp sponge or cloth helpful to wipe the tip of the iron clean periodically. An inexpensive wire stripping tool is helpful, but some people prefer a single-edged razor blade for removing the insulation. SOLDERING INSTRUCTIONS A good solder connection does not require a large amount of solder around the joint. A well-made connection looks smooth and shiny because the solder flows into the joint when both parts are hot enough. There are four steps to making a good solder connection: 1. Make a good mechanical connection. 2. Heat hoth parts with the tip of the iron af the junction. 3. Apply solder to the junction until it melts and flows. 4. Allow the connection to cool undisturbed. ALL SOLDERING MUST BE DONE WITH A GOOD GRADE OF ROSIN CORE SOLDER. Under no circumstances should acid core solder be used. Unmarked solder, cheap solder or any of doubtful origin should be discarded, and separate solder fluxes should never be used. The warranty is voided on any equipment in which acid core solder or acid type fluxes have been used. Silver solder is not suitable. The recommended solder is 60/40 (60% tin, 40% lead) ROSIN CORE. Do not con- fuse this with 40/60, which ig harder to use. If vou have a soldering gun, it should be used with care, especially when working on the circuit boards. A soldering gun can provide more heat than is necessary, with some risk that an unskilled user might damage the board, and because it requires some time to heat each time the trigger is squeezed, many users tend to make poor solder connections simply because they do not wait long enough for it to reach its operating temperature each Lime. You should realize that delicate components such as transistors are less likely to be damaged in the soldering process if you use a hot iron for a short time, rather than a cooler iron for a longer period. You will also make a better connection with the hot iron. If you keep the iron clean by wiping the tip frequently, and occasionally add a small amount of solder to the tip, it will aid the transfer of heat to the connection. Do not allow too much solder to build up on the tip, though, or it may fall onto adjacent circuitry. One of the best ways to make a good mechanical connection is to bend a small hook in the end of the wire, and then to crimp the hook onto the terminal lug. The amount of bare wire exposed need not be exactly 14-inch, but if it iz too long, the excess might touch another terminal lug or the chassis. Do not wrap the wire around the lug more than one time, as this makes the connection difficult to remove if an error is made. 14 В Да WRONG When soldering a lead to an eyelet on the cir: cuit board, the SCA-80 makes it easy to apply the iron to one side of the board while the tinned wire end is pressed into the golder-filled eyelet from the opposite side. When the eyelet is heated, the wire enters easily, but be careful that you do not push the wire all the way into the eyelet up lo the insulation. If you do, you will not be able to see if you have made a secure connection, or if more eolder is needed to provide a smooth flow from the wire, to the eyelet, and onto the circuitry on the board. WIRING THE KIT The position of all wire leads should follow the diagram and photograph closely, bearing in mind that the pictorial diagram has necessarily been distorted somewhat to show all connections clearly. See that uninsulated wires do not touch each other unless, of course, they are connected to the same point. It is especially important that uninsulated wires or component leads or terminals do not touch the chassis accidentally. Whenever one wire is to be soldered to a connectión such as a lug or a transistor lead, the instructions will indicate this by the symbol (5). If more than one wire is to be soldered to the same point, the instructions will cite the number of wires that should be connected to that point when it is to be soldered. If no soldering instruction 1s specifically given, do not solder; other connections will be made to that point before soldering is called for. When the instructions refer to “tinming” a wire, apply the iron to the bared wire end, and after a moment, touch the solder to the wire so that the solder lightly coats the wire. This makes it easier to get a good connection when the wire is inserted into an evelet, for example, Components such as resistors and capacitors are marked indrvidually with their values, or with a color code, The color code will be given in the instructions when needed. The first color band on a resistor is the one nearest the end. Any fourth color band may be ignored. Check your work after each step, and make sure the entire step has been completed. When vou are satisfied that it has been correctly done, check the space provided and go on to the next step. Be sure vou read carefully the explanatory paragraphs in the assembly instructions. Many of the wiring steps will call for “preparing” а wire of a certain length and color. This involves cutting the necessary length of wire and stripping 14 inch of insulation from each end. This is most easily done with wirestrippers, but diagonal cutters can be used if vou are careful not to nick the wire and weaken it. With stranded wire such as transformer leads and line cords, be particularly careful not to cut the strands when stripping the ends. Two coils of heavy gauge wire are supplied for special use indicated in the instructions. Although the SCA-800 includes protective circuitry to prevent breakdown in use, only vou can prevent breakdown resulting from improper construction. Transistor equipment, unlike much tube equipment, will not tolerate wiring errors, sloppy or incomplete soldering, TAKE THE TIME TO BE NEAT AND ACCURATE, and your amplifier will operate properly at first, and for many years to come. The four circuit boards and the four power transistors have been in-circuit tested before leaving the factory. This assures that all of the semi-conductors, as well as most of the other parts, are performing to specifications. Only the interconnection of these parts is left to vou. To protect the selector switch it is suggested that it be left in 1s protective wrapping until called for in the instructions. Two sizes of screws and nuts are supplied with the kit: the small #4 size, and the large #6 size. For your convenience, no #4 lockwashers are supplied. Use #6 lockwashers when #4 hardware is called for. A “set” of hardware includes one each screw, nut and lockwasher. All mounting screws are installed from the outside of the chassis, and a lockwasher is used under each nut, except when otherwise specified. Also supplied are 8 #6 self-tapping screws, which can be identified by their tapered shape and scored tip. These should be separated from the rest of the hardware and set aside until called for in the instructions. Mechanical Assembly Place the chassis front panel before vou, oriented as in the pictorial diagram. 1( Select the QPTT rocker switch (16 lugs), two of the 34" screws, the two brass plated (longer) tubular spacers, lockwashers and nuts. Note that one 10 position of the rocker has a spring-return to center. Insert the screws through the panel at location OS, slip the spacers over the screws, and install the swilch so that the spring-return position 18 towards the center of the panel. The remaining switches do not require either lockwashers or nuts as they have tapped, extruded mountings. 2( )Select the power switch (with the clear rocker) and two #4 (smallest) screws. Install it in location PS so that the two small wires coming from inside the switch are toward the bottom of the chassis (where switch OS was installed). 3{ Select one of the two DPTT rocker switches (8 lugal, two of the 34" natural finish tubular spacers, and two 34” screws. Install the switch at location BS. 4{ )Select the remaining DPTT rocker switch and install it im location FS with the remaining tubular spacers and 34" screws. 50 JSelect the two DPDT rocker switches (6 lugs? and install them in locations LS and MS with #4 screws. GC }3elect the phone jack, and place the flat 44" washer over the threaded portion, followed by the 34” lockwasher. Install the jack in location HP with the lugs positioned as in the diagram, and fasten with a 45" nut. 70 Select the volume control (8 lugs), part #177254. Insert the control in location VC. Be sure the locating tab on the control engages the small hole in the front panel, and fasten with a 45" nut. 8( Install the balance control, part #167224, In similar fashion in location BC with a 33" nut. 9( Install the bass control, part #167514, in similar fashion in location DB with a 44" nut, 100 ¿Install the treble control, part #167404, in similar fashion in location DT with a 34" nut. This completes the mechanical assembly of the front panel. Location 55 is vacant for the present. Set this assembly aside, and place the back panel in front of vou, oriented as in the pictorial diagram. 11{ jSelect one of the two G-socket input strips, four #4 screws and nuts, three lockwashers and one ground lug. All screws are inserted from the outside of the panel. The strip is mounted on the inside of the panel, with the ground lug used in place of a lockwasher over the upper left screw. As vou tighten the screws, orient the ground lug as in the diagram, and be sure that none of the metal socket mounts contact the chassis. 12( Install the remaining 6-socket input strip in the same manner, using a ground lug on the upper left serew. 130 Select one of the two 4-lug screw terminal output strips and two sets of #4 hardware. Place the sirip on the outside of the panel with the lugs toward the inside bottom of the panel. Insert the screws first through the strip, then the panel, fastening them with a lockwasher and nut. 14( Install the remaining 4-lug screw terminal strip in the same manner. 15( Install one of the AC outlets in the upper location (marked unswitehed on the panel) with two sets of #4 hardware with the flange inside. 160 Install the other AC outlet in the lower location with two sets of 44 hardware. 17( Install the 4-lug terminal strip TS with one set of 44 hardware in the hole between the two AC outlets. Note the lug placement in the diagram. 18( Install the fuse holder below the black AC outlet, The rubber washer stays outside the panel, and the fat side of the mounting hole engages a similar flat on the holder for proper orientation. Secure it with the lockwasher and nut. This completes the mechanical assembly of the back panel. One large hole remains vacant for the present. Set this assembly aside, and place the main chassis bottom plate in front of you, flanges upwards. 19( Select the four rubber feet, and four sets of #6 hardware. A fool is mounted in the hole in each comer of the chassis by tuming the bottom plate over, placing the foot over the hole, and forcing the screw through the foot until the screw head is recessed. The foot mounted in the corner where the power transformer will be located should be mounted loosely, The other three should be fastened securely, but not so tightly that the foot becomes distorted, The next 4 steps describe the installation of the four capacitor mounting brackets, All mounting screws are installed from the outside (bottom) of the chassis, One set of #6 hardware is to be installed in each bracket clamp before mounting. In each case refer to the diagram for the correct orientation of the clamp, and also for the direction of insertion of the clamping screw. This will facıhtate servicing access if required in the future. Because the brackets are flexible, you will find that the capacitors will be held most securely if they are temporarily slipped into each bracket for sizing when the bracket mounting bolts are tightened. While squeezing the bracket around the capacitor, tighten all the mounting bolts, starting first with the bolt farthest from the clamp. Then remove the capacitor. De not remove the outer insulation from any of the three largest capacitors. 20{ JSelect the 1%” diameter (smaller) bracket and three sets of #6 hardware. Install it at the left of the chassis as in the diagram. 21( )Select one of the three larger (27 diameter) brackets, four sets of 46 hardware, and install it as shown in the diagram at the rear of the chassis. 22( Install another of the brackets in the right front corner of the chassis with four sets of #6 hardware, 23( Install the remaining bracket on the right side of the chassis with four sets of #6 hardware. 240 Install the two “U" shaped brackets in an upright position in the single holes near the front of the chassis with two sete of #6 hardware. 25( Remove the foot in the right rear corner of the chassis and install the power transformer with the two red leads toward the center of the chassis, using three additional sets of #6 hardware. Reinstall the foot and tighten it securely, 26; Select one of the two long narrow circuit boards, PC-17, and four sets of #4 hardware. To facilitate wiring in later steps, you should remove the solder which fills eyelets 3, 4, 11 and 12 of this board. Heat each eyelet in turn with the soldering iron, and then clear the eyelet with a toothpick. Be careful that no solder splashes onto other parts of the circuitry on the board. Install this board on the rear inside of the two "U" shaped brackets with the row of eveleis on top, and the components on the side of the board nearest the power transformer. 27( Install the remaining PC-17 board with four sets of #4 hardware on the front outside of the two brackets, with the eyelets on top, and the component side of the board nearest the power transformer. Wiring the Main Chassis The next 4 steps describe the installation of components on the power supply circuit board PC-19, The placement of each part is marked on the side of the board on which most of the components are mounted by lines to the holes into which its leads will be inserted, Dotted lines indicate parts which are mounted on the reverse (copper) side of the board. Except where specifically indicated otherwise, the parts should be mounted tightly against the board, just as vou see those on the other circuit boards mounted. Each part will be identified by a part number, color code, or written value. First bend the leads to fit the space between the marked holes, then push the leads through the holes and spread them slightly to hold the part in place for soldering. Solder each lead and every evelel carefully to the copper foil, being sure the solder flows all around the lead and smoothly onto the copper, without any bridges to other parts of the circuitry. Cut off all excess leads. The copper side of the board has been coated with a corrosion inhibitor which is also conducive to soldering, but there is no substitute for good soldering technique. 1{ Install the 68 ohm resistor (blue-gray-black) R21. 2( Install the four silicon rectifier diodes #544322, D4, D5, D6 and DT, Be certain the markings are all faced the same way, with the The ones supplied may be any > of the three types shown in the illustration. Although different in appearance, they are electri- Solder. cathode end nearest resistor R21. cally equivalent. Solder. CATHODE fi ——E—— 31) Install the .01 mid 500 volt disc capacitor C37 on the inside leads of diodes D4 and D6 (see board diagram page 18), Cut each capacitor lead to 167, hook it around a diode lead, and solder each. 4( Install the two 7 wait, 575, 400 ohm resistors R16 on the circuit board, De not mount them flush against the board. Allow at least 14", but nol more than 14" space befween the resistor body and the board for ventilation, as these get quite hot in normal use. If these resistors are supplied with 14” molded feet, the feet may be mounted Aush to the hoard, Solder each lead to the evelet, and across the evelet to the copper circuliry. The most common error in assembling this kil is incomplete soldering of these evelets, and those in the following step, to the board. 5( Install the two remaining 7 watt, 400 ohm resistors R17 on the reverse (copper) side of the board, leaving between '4” and 14" ventilating space. Solder these on the copper circuit side of the board. GC To make connections to the evelets easier, “tin” all 9 numbered eyelets on the board now. Apply enough solder to fill each eyelet, and to solder it securely to the adjacent copper circuitry. The wires in the next three steps are to be connecled to evelets on the circuit board. À good connection is more assured if the wire is first “tinned” by heating it and applying a small amount of solder to the tip before it is connected to the evelet, In most cases, it is easiest to heat the eyelet from the copper side of the board when the wire is inserted. Hold the wire steady while the connection cools, and then wiggle it to be sure the connection is secure, There should be a smooth flow of solder from the wire to the evelet, and across the evelel to the board. If in doubt, reheat the connection and add a bit more solder. ТО Strip 114 of insulation from one end of the coil of black hookup wire, “tin” the tip, and connect this end to evelet #7 from the copper side of the board. (S). Then clip off this wire at the insulation. This is the easiest wav to handle such a short uninsulated wire length. SC ) Prepare a 414” green wire, “tin” both ends, and connect one end to evelet #6 from the front (diode side) of the board, (5). 9( 3 Prepare a 634” red wire, “tin” both ends, and connect one end to evelet #5 from the front of the board. (8). 100 The two right-angle brackets have one leg shorter than the other. The shorter leg is to be mounted Lo the power supply board, and the longer one to the chassis. They fasten to opposite sides of the board, projecting outwards, One brackel makes conlacl with the copper circuitry adjacent to evelet #7. The other is mounted below the diodes. Use two sets of 44 hardware to mount the brackets to the board. In both cases, the screw is inserted first through the bracket, and then through the board, 12 11{ )With one set of #6 hardware mount the FC-19 board on the chassis. The ungrounded bracket (below the diodes! is fastened at the hole nearest the power transformer at the rear of the chassis. 12{ J Select the two remaining ground lugs, and one #6 screw and nut, Pass the screw through the chassis, through the second PC-19 bracket, and then through the two ground lugs arranged in a "VV", and fasten with a nut. A total of 5 wires will be connected to these ground lugs. It makes no difference which is used for any wire. 13( Connect the short bare wire from eyelet #7 to one of the ground lugs. The following 4 steps describe the installation of the power transistors on the black aluminum heat sinks. This requires the application of the white silicon thermal compound supplied in a capsule. IL is necessary to assure good heat transfer while maintaining electrical insulation. The quantity supplied is far in excess of what vou will need. A uniform film is required on one of each pair of mating surfaces. This thermal compound can be most annoving if care- lessly handled. Stray smudges can make vour finished amplifier look sloppy. Therefore, clean up any excess with paper tissues as vou go along. lt is difficult to remove from clothing, and the best removal agent, if needed, is a freon degreasing agent available in à pressure spray can at elec- tronic supply houses. Une of the easiest ways to handle this compound is to apply ¡t with the blade of a screwdriver. However, the screwdriver used should be other than the one emploved to install the hardware, The thermal compound must first be applied to the flat base of the transistor. Next the insulator is added over the transistor pins ( they are off-center, so orient the insulator properly), and compound is applied lo its surface as well. Only a thin film of compound is necessary. For easier handling, vou may avoid applying compound to the outer edges of the mounting holes. Now carefully wipe off] any compound from the transistor pins. Then orient this transistor assembly and the heat sink (see NOTE in Detail A) so that the transistor will be installed in the deeper récess of the heat sink with the pins protruding adjacent to the exterior “C" channels. Be sure the correct transistor assembly (with or without the red dot) 15 first positioned to align the pins with the off-center smaller holes in the heat sink rib, and then install the transistor in the appropriate location, Apply a slight twisting motion to assure uniform distribution of the compound, The insulator should lie flat between the heat sink and the transistor, and thus be visible all around the transistor. Then install the appropriate hardware as each step indicates. 140 ) Select a heat sink, an output transistor 571844 unih a red dot (Fart #338-2} one of the thin plastic transistor insulators, the thermal compound, two nylon shoulder washer/spacers, lwo #6 screws, a lockwasher, a ground lug, and two 46 nuls. Apply the thermal compound to the transistor and insulator, and install this assembly in position (6 (note that Q5 shows the mounting sequence, and Q6 is already installed in the drawing). Pass a screw through the transistor mounting Mange nearest the outer (left in the drawing) edge of the heat sink. From the other side of the heat sink rib install a nylon shoulder washer/spacer (smaller diameter first) over the screw so that it fits inside the mounting hole. Follow with a lockwasher and nut, finger tight. Install the second screw and shoulder washer in like fashion, followed by the ground lug and nut Be sure the transistor pins are centered in their clearance holes, orient the ground lug as in Detail B on the next page, and securely tighten the hardware. 15¢ Select a transistor 4571844 which does not have a red dot (Part +4836-1) an insulator, two shoulder washers, two #6 screws, a lockwasher, a ground lug, and two #6 nuts. Apply the thermal compound and install this transistor in the (5 position on the same heat sink, with the ground hug on the outside (right) edge screw oriented as in Detail B on the next page, and tighten the hardware. 164 ) Select the remaining heat sink, the other 3571844 transistor with the red dot (Part 2338-2) and an insulator, two screws, two shoulder washers, lockwasher, ground lug and two nuts. Apply the thermal compound and install this transistor in the Q6 position, orient the ground lug properly and fasten it securely, 17 — Select the remaining transistor without a red dot | Part #338-1) the insulator, two screws, nuts, and shoulder washers, a lockwasher and ground lug. Apply the thermal compound and install it as Go, Check the ground lug and tighten the hardware. You have concluded the need for the thermal compound, 80 it may be disposed of. Wipe off any excess, and particularly wipe clean the ground lugs and the transistor pins so that proper solder connections may be made to them. Each of the two amplifier channels comprises a heat sink assembly, just completed, and a preassembled and tested circuit board. The four items fit together like the sides of “C” CHANNEL 06 — RED DOT 338-2 — a box, with two adjacent sides (heat sink and board) com- prising one channel. Be careful not to bend the transistor pins, for it is important that neither the pins nor connections to them be allowed to touch the heat sink, Detail B shows the wiring to the left channel heat sink, with the connections identified by a letter which will follow the number of the transistor, as Q5-E. For convenience you may wish to mark these letters on the heat sink with a soft pencil. Keep your wiring neat, and observe the direction in which each wire 1s to be oriented on the diagram before soldering. Different right channel wire lengths are given in italics rin parentheses), In some places the instructions will tell you to form a loop in some of the wires. This is done with the tips of long-nosed pliers, to produce a closed ring at the end of the wire that is just large enough to fit snugly over the transistor pins, It is then squeezed around the pin with the phers to hold it for soldering. While excessive heat may damage any transistor, the silicon types used in the SCA-800 are very rugged, and it1s more important that vou have the transistor pin and the wire vou are connecting to it hot enough before you apply the solder, so that the solder will flow quickly over the junction, giving vou a smooth connection. A small drop of solder on the tip of the iron will assist you in heat transfer and good soldering. If the solder does not flow easily around the connection, allow it to cool, and try again after the tip of the iron is again hot. To avoid short circuits to the heat sinks, all connections must be made to the tip of the transistor pins, and solder must not be allowed to flow into the recess formed by the hole in the heat sink. = = Ея ый THERMAL COMPOUND я A A NOTE: IT IS ESSENTIAL THAT THE HEAT SINK BE ORIENTED 50 THAT THESE OFF-CENTER HOLES ARE POSITIONED AS SHOWN WHEN INSTALLING THE TRANSISTORS, | Detail A 13 18( 19( 20¢ 211 AA 231 24( 261 Orient one of the heat sinks as in Detail BE, with the ground lug on the end to the right, Select one of the 0.47 ohm resistors (yellow-violet-silver) and trim the leads to a length of 34". Bend the leads to form a “UL”, and form a loop in one lead. Tuck the resistor into the inner-most channel on the heat sink, and pass the tip of the straight lead through lug Q6C. Connect the loop to Q5E. (5). )Prepare a 2%” green wire, and form a loop at one end. Connect this from the right to Q5B. (8). )Prepare a 314” green wire and a 2147 green wire. Connect one end of each wire from the right to lug Qo. (5-2), Put a nght-angle bend near the end of the shorter wire for later identification. )Prepare a 314” black wire, and form a loop at one end. Connect this from the right to Q6E. ) Prepare a 514" black wire, and form a loop at one end, Connect this from the left to Q6E. (8-21. 1 Prepare a 47 green wire and connect one end from the right to lug Q6U. Bend a hook at the end for later identification, yPrepare a 6%" green wire and connect one end from the left to lug Q6C. (8-3). ) Prepare a 316” green wire, and form a loop at one end, Connect this from the right to QB. 151. \The heat sink assembly is to be mounted with 4 of the self-lapping screws initially set aside. Tilt the chassis upright on the power transformer. Place the heat sink between C9 and Cl1 on the left side of the chassis, with the solder lugs toward the center of the chassis, and Q6 next to the chassis. Bend the two wires from Q6 towards the chassis rear. Thread the screws into the four “C" shaped channels from the bottom, Do not tighten these screws until all four are properly threaded into the heat sink. Fasten them securely, but do not apply excessive force or the threads may strip. ai 284 а HU 31( Gé an 341 do dE ¡Orient the second heat sink as in Detail B. Trim the leads of the remaining 0.47 ohm resistor (yellow-violet-silver) to %”, bend them to forma “U”, and form a loop in one lead. Tuck the resistor into the channel, slide the straight lead through lug Q6C, and connect the loop to Q5E. (8). \Prepare a 244" red wire, form a loop at one end, and connect this from the right to Q5B. (8). Prepare a 612” red wire, and a 214" red wire. Con- nect one end of each wire from the right to lug G5C. (5-2). Put a right-angle bend near the end of the shorter wire for later identification. i Prepare a 314” black wire, form a loop at one end and connect this from the right to Q6E. \Prépare a 644” black wire, form a loop at one end and connect this from the left to Q6E. (5-2). ) Prepare a 47 red wire and connect one end from the right to lug OGU. Bend a hook in this wire for later identification. > Prepare a 615” red wire and connect one end from the left to lug Q60, (5-31, } Prepare a 316” red wire, form a loop at one end and connect this from the right to Q6B. (5). y Mount this heat sink facing the other one with the remaining 4 self-tapping screws as before. Bend the two wires from Q6 at the bottom, as well as the longest top wire, towards C9. Lav the chassis flat, and check both heat sinks to be certain the connections to the four solder lugs do not touch the black heat sinks, and that all transistor pins are centered in their holes, y Now “lin” the free ends of each of the wires on the two heat sinks, to facilitate their later connection to evelets on the circuit boards. Keep the wires clear of the transistor pins when tinmng them, to avoid the possibility of a solder splash making a short circuit, Ha (652) A Yo EA Te a TT TT TL aa e a e al | aji 14 Detail E 37¢ Select the long black wire which protrudes from the bottom of each heat sink (from Q6E). Connect these two wires to one of the ground lugs at the power supply board, Soldering of wires lo these luge will be easier if they are all brought up through the lug from underneath. 380 Connect the green wire protruding from the bottom of the left heat sink to evelet #4 of PC-19. (8). 39¢ Connect the red wire protruding from the bottom of the right heat sink to eyelet #3 of PC-19. (5), Select both of the PC-18 amplifier boards. Be particularly careful handling these boards, for they represent a subetantial portion of the cost of the SCA-S50G. The transistors stand upright on the boards, held in place by their leads, Careless handling can unduly flex and possibly break the leads. In addition, the same silicon compound you used in mounting the output transistors is also already applied between the driver transistors, Q3 and 4, and their smaller heat sinks on the boards. Make sure each of the 4 transistors on each board is standing up so that their leads do not touch one another. There should be no need for you to solder to any of the components, since all connections will be made to evelets along the top edge of the board. However, if the occasion arises, remember that excessive heat will damage any transistor, though these are rugged silicon types. When soldering to a transistor lead, it is important that the iron and the junction be hot enough when you apply the solder, so that the solder will low rapidly into the junction. Then you can remove the iron quickly and allow the connection to cool. Be careful that no solder splashes onto the circuitry where it may cause a short circuit and damage the amplifier. Only a small amount of solder 18 usually needed on any connection. The instructions will refer to the front or rear amplifier (PC-18) or preamplifier {PC-I7) circuit boards, as well as to inserting the wire from the forward side or back side of each board, Forward refers to the side nearest the front of the chassis. The forward and back designations will be im parentheses. 400 1On each of the PC-18 boards you will note two un- used holes below evelets 11 and 12 Select two 10000 ohm (brown-black-orange) resistors and trim their leads to 16”. Bend the leads in a “U”, and install one of these resistors on each circuit board through these holes. Heat the circuitry on the opposite side with the iron to melt the solder while you push the leads through the board. Mount the resistor flush to the board, and cut off the excess leads. Be sure the connections are well soldered. 41( JThe PC-18 boards slide into the pairs of “C" shaped channels on the heat sinks, resting on the mounting screws at the bottom. Orient one of the boards with the eyelets uppermost, with the components toward the front of the chassis, and the circuit side toward the power supply board. Slide it into the front pair of channels. 42( Connect the red wire from evelet #5 of PC-19 to evelet #6 (back) of PC-18. (8). 430 Connect the shorter black wire from Q6E of the right heat sink to evelet #2 of PC-18. (5). 44({ Connect the hooked red wire from Q6C to eyelet #8 of PC-18. (5). 450 Connect the red wire protruding the shortest distance above the heat sink (from Q6B at the bottom of the heat sink} to eyelet #3 of РС-18, (5). 461 Connect the red wire with the right-angle bend (from lug G5C) to evelet #4 of PC-18. (5). 47( )Connect the remaining shorter red wire (from Q5B) to evelet #5 of PC-18, (5). 48¢ Install the other PC-18 board in thé rear pair of channels with the eyelets up, and the components side facing to the rear. Note that while the preamplifier boards were installed facing the same way, the amplifier boards face in opposite directions. The following 6 steps all refer to connections to be made to the rear PC-16, 49( Connect the creen wire from eyelet 6 of PC-19 to eyelet #6 (back) of PC-18, (8), 500 )Connect the shorter black wire from Q6E of the left heat sink to eyelet #2. (5). 510 Connect the hooked green wire from Q6C of the heat sink to evelet #8. (8S). 52( Connect the green wire protruding the shortest distance above the heat sink (from Q6B) to eyelet 43. (5), 5370 JConnect the green wire with the right-angle bend (from lug ОБС) to evelet #4. (5). 54( Connect the shorter of the two remaining green wires (from Q5B) to eyelet #5. (5). 55( Install one of the large 5000 mfd capacitors in position C9 at the rear of the chassis. Seat it firmly to the chassis with the red lug to the front and tighten the bracket clamp. 56( JConnect the long red wire from lug Q5C of the right heat sink to the red lug of C9. Position the wire over towards the left heat sink, and then back to CO, Now turn to page 19. 15 TAFE QUT SPARE | — — o TAPE AMP | TUNER | | PHONO | SPECIAL | a ня SELECTOR 52WITCH 15 SHOWN | | IN THE COUNTERCLOCKWISE cas POSITION, REAR WAFER № SHOW LEFT). Cid “9 | 7 + a REAR SIDE Е Ras S.5- YIEwED FROM EMOB ENG ——vww F dé | ww = === FILTER MONITOR [o R4é (RIGHT! cis SE © ТО R45{RIGHT) TT MODE ] [ BASS | | |C33 | VOLUME BALANCE TREBLE "ито шит Ew = ve" OE aE a LOUDNESS = = = — |- E (33 т т v 10 EYELETS OM ALL WIRING NOT SHOWM FOR THE RIGHT CHANNEL 15 THE SAME AS THÉ LEFT CHANNEL, WHICH 15 SHOWN. RESISTOR AND CAPACITOR NUMBERS ARE THE SAME FOR THE PARTS OM BOTH CHANNELS. PC 17(RIGHT] 16 BLACK WHITE | VICILET- 1 HETE VELLO e PC-16 #1 0 (RIGHT pr = | = v VOLTAGE TEST POINTS Measured with VTVM (TVM) at rated AC line voltage, 8 ohm load, shorted input. All voltages are DC unless specified AC, Voltages not shown are not significant for servicing purposes, as they may vary widely with different transistors and still be normal. Transistor lead voltages shown may vary 20% or more. Other points should be within 107%. PC-19 #1 #2 #0 #4 #5 1.4 to #6 1.6" #7 #5 we T1 74 ab 36 37.0 37.6 0 | 54 АС* “Measured between eyelets Q7 648 QF glo E 1 8. 1.2 В 7 15 94 18 С 1.5 10 15 94 Capacitor C-11 A 7 Ш 4 Mie 17.5 SCHEMATIC DIAGRAM 17 COMPONENT VALUES All resistors are 14 watt, 5%, unless otherwise indicated. PART # PART # PART # R1 470 ohms 113472 H30 56,000 ohms 113563 С11 70)míd iv 7hv. à R 2 4,700 ohms 113472 Ral 120 ohms 113121 700 mid E 60v. MM R 3 30,000 ohms 113303 R32 330 ohms 113331 S00 mid @ 20v, = 204228 R 4 150 ohme 113151 R33 33.000 ohms 113333 C13 27 pi 244271 R 5 100,000 ohme 113104 Rad 3,300 ohms 113332 Cl4 5 mid, 15v. 283505 R 6 1,000 ohms 113102 R35 4,700 ohms 113472 C15 0.01 mid, 59% 265103 R 7 1,500 ohms 113152 R36 390 ohms 113391 C16 3300 pf, 5%, 265332 R € 330 ohms 11333] R37 120,000 ohms 113124 C17 0.022 mid 265223 R 9 2,200 ohms, 1 watt 116222 R38 270 ohms 113271 C18 6 mid, 15v. 283505 R10 1,000 ohms 113102 R39 4,700 ohms 113472 C19 100 pf, 5% 245101 R11 10,000 ohms 113103 Rá40 68 ohms, 10% 112589 C20 50 mid, 25v. PA3516 R12 10,000 ohms 113103 Rál 4,700 ohms 43977. C91 0.015mid, 597 265153 R13 68 ohms 103680 R42 10,000 ohms 113103 (99 (056 mid Or de R14 68 ohms 103680 R43 120 ohms 113121 (23 100 “a > mid, Zw. 281107 R15 2,200 ohms, 1 watt 16222 R44 47,000 ohms 113473 C94 50 mid 25v Sa a R16 400 ohms, 7 watt, 5%; 120401 R45 10,000 ohms 113103 C25 0 14: í E Е R17 400 ohms, 7 watt, 597, 1206401 R46 10,000 ohms 113103 уро РОТЕ adas R18 4.7 ohms, 1 watt, 10% 125040 Rá47 10 ohms, 10 watt, 10% 120100 C26 220 pf 245221 R19 0.47 ohms, 2 watt, 10% 128004 C1 0.33 mid 263334 (27 50 mfd, 25v. 283516 R20 3.3 ohms waa C2 220 р! 245221 C28 500 mid, 2v. 281507 R21 68 ohms 103680 C 3 35 п 4, 30м., non-pol 283066 29 0.068 mid 265683 R22 10,000 ohms 113103 C 4 35 míd, 30v., non-pol, 283366 СЗО 0.1 mid, 5% 269104 R23 8,200 ohms 113822 C5 500 mfd, 15v, 283507 C31 0.015 mfd, 5% 265153 R24 18,000 ohms 113183 C6 047 mfd, 100v., non-pol, 264474 C32 0.22 mid 265224 H25 4.7) ohms 113472 C 7 5000 mid, 80v. 284506 C33 27 pt 244271 R26 33,000 ohms 113333 C 8 0.1 mid, 100v. 264104 C34 0.02 mid 227203 R27 3,300 ohms 113332 C 8 5000 mid, Biv, 2845048 Con 0.02 mid 227203 R28 47,000 ohms 113473 C10 0.01 mid, 100. 244104 C36 0.01 mfd 244104 R29 4,700 ohms 113472 C12 68 pf 237680 037 0.01 mfd disc, HO. 228103 PART # PART # F 1 Fuse, 2amp slo-blo 342020 Volume control 250,000 ohms tapped 177254 F 2 Fuse, 1 amp slo-blo (alternate) 342010 Balance control 220,000 ohms special 167224 L 1 114 inches of #16 insulated wire 319913 Bass control 50,000 ohms special 167514 T 1 Dynaco power transformer 10490E 464019 Treble contral 40,000 nhms special 167404 D 1 zener diode, 5.1 volt, 5%, 400) mw 540405 BY iB i D ? silicon diode, 0.8 volt max. drop @ 140 ma. 544015 5 © i D 3 silicon diode, 0.8 volt max, drop @ 140 ma. 544015 Го D 4 silicon diode, 3 amperes, 200 pry, 544322 D 5 silicon diode, 3 amperes, 200 prv. 544322 D 6 silicon diode, 3 amperes, 200 pry. 544327 D 7 silicon diode, 3 amperes, 200 pry. 544322 Q 1 BCIOBA 170-260 Beta (Y 2 та 572108 Q 2 2N5320 140-260 Beta, 90 Y, r=5E0 ( 50 ma 572002 Q 3 TIP31C 577031 Q 4 TIP32C 567032 Q 5 2NA772/571844, 40-90 Beta @ 1 A 338-1 Q 6 2N3772/571844 Red Dot, 60-90 Beta @ 1 A 338-2 Q 7 BCIE 240-500 Beta té 5 volts, 2 ma 512109 Q 8 BCIE 240-500 Beta & 5 volts, Z ma 572109 Q 9 BC109B 240-500 Beta @ 5 volts, 2 ma 572109 Q 10 BC109B 240-500 Beta @ 5 volts, 2 ma 572109 Cr LT | 57( Sl 9 60 BIC )Connect the green wire from lug ОБС of the left heat sink to the red lug of C9. ) Prepare a 314” red wire, Tin one end and connect it to evelet #2 (forward? of the power supply board. (5), Connect the other end to the red lug of C9, (5-3). ) Prepare a 5” length of the heavy gouge wire. Con- nect one end to the black lug of C9, (5). Connect the other end to one of the ground lugs at PC-19, bending it up from underneath. ) Each of the two coils of heavy gauge wire will be formed into a coil around one of the large C7 5000 mfd capacitors. To facilitate forming these coils, vou will use the smaller capacitor C11 (3- section electrolytic) as a form. Strip 147 of insulation from one end of the coil, and form a small hook at that end. Hook the wire around one of the outside ground lugs of Cll, bring it across the capacitor past the opposite ground lug and bend it sharply down over the rim of the capacitor. About 14” below the rim, bend it sharply to the right to start the wire in a counter-clockiwise direction when looking at the top (lug endi of the capacitor, Wind the wire tightly with the turns as close together ns possible for at least 24 turns. Do not cut off the remaining wire. You must hold the “start” while you wind, and feed the wire by unwinding the coil supplied. You may find it easier if you place the capacitor inside the supplied coil while you form the new coil. Pulling the wire straight off the coil may cause it to kink. This is the most tedious part of the kit. Take the time to do a good job. When you release vour hold, the wire will spring loose to form a larger diameter coil Disengage the hook from the lug and slide the coil off CIT. Select one of the larger 5000 mid capacitors and fit its lug end into the part of the formed coil that is farthest from its hooked end. Guide the coil onto the capacitor a loop at a time, as though you were threading it on, With care and patience you can avold deforming the coil and keep il snug. When the coil is all on the capacitor, slide it around until the hook will fasten through the black lug after passing behind the red lug, and solder the black lug. (5). )Form a second coil exactly as before. Install this coil on the remaining 5000 mid capacitor, and solder the hook to the black lug. 18). ¡Select one of the capacitors with the coil wound around it, count 17 complete turns, and install it with the red lug to the front in position CTL next to the power transformer. At this time the position of the lugs is rotated 90% from its final position as shown in the pictorial diagram. Tighten the bracket clamp to secure the capacitor, make sure the coil is snug and tightly wound, and measure 3” of wire protruding past the side edge of the chassis. Cut off the excess. Strip 14” of insulation from the end, and hook the end over the chassis to secure it temporarily. 62( yInstall the other capacitor and coil in position CTR with the red lug to the front, count 17 full tight turns and only 14” of wire protruding past the side edge. Cut off the excess, strip 14" of insulation from the end, and hook it over the clamp lo secure it. Gad ( j Install the 3-seclion capacitor C11 in ils bracket al the left of the chassis. Seat it firmly to the chassis wilh the lugs oriented as in the diagram, and tighten the bracket clamp. G4 ( In four of the next five steps a wire is called for which has extra insulation removed from one end, This longer bared end is to be connected to correspondingly numbered evelets in the front and rear preamplifier boards, First push it through the rear board from the back, and then heat the evelel on thé front board as vou push the tip of the wire through the eyelet and solder it in place, Then apply solder to the rear board to solder that evelet. 690 )Prepare a 3%" black wire with 114" of insulation removed from one end. Connect it to evelet #3 of each PC-17 board. (51. Connect the other end to ground lug D of CII. 66( J) Prepare a 6%” black wire with 114” of insulation removed from one end. Connect it to evelet #11 of each PC-17 board. (51. Connect the other end to ground Tug D of C11. (5-2). ) Prepare a 4% red wire wilh 14" of insulation removed from one end. Connect il to evelet #4 of each PC-1T board. (5), Connect the other end to lug C (semi-circle) of CII. 67 ( 68( ) Select a 10,000 ohm resistor ( brown-black-orange), and trim the leads to no more than 34”. Connect one end to lug © (semi-circle) of C11. 18-2}, Con- пес! the other end to lug A (triangle) of C11, 69{ Prepare a 739" red wire with 116” of insulation removed from one end. Connect it to eyelet #12 of each PC-17 board. (8), Connect the other end to lug B (square) of (C11. TH Select a 4700 ohm resistor vellow-violet-red | and irim the leads to no more than 45". Connect one end to lug B (square) of Cll. (8-2). Connect the other end to lug A (triangle) of (C11. 710 )Prepare a 315” black wire. Tin one end and connect it to evelet #11 (forward) of the front empli- fier board PC-18 (5). Connect the other end to ground lug E of C11. 14 Tel 730 Tel Tol y Prepare a 47 black wire. Tin one end and connect it to evelet #9 (forward) of the front PC-18. 15). Connect the other end to ground lug E of C11, ) Prepare a 6%” black wire. Tin one end and connect it to eyelet #9 (forward) of the rear PC-185. (5). Connect the other end to ground lug E of C11. ¡Prepare a 16” black wire. Tin one end and connect it to evelet #11 (forward) of the rear PC-18. (5). Connect the other end to ground lug E of C11. (54), Be sure all of these wires are soldered. Prepare a 414” red wire, Tin one end and connect it to evelet #10 (forward) of the front PC-18, (8). Connect the other end to lug A (triangle) of C11. 760 Prepare a 716” green wire, Tin one end and connect it to eyelet #10 (forward) of the rear PC-18 (5). Connect the other end to lug À (triangle) of CII. 770 )Prepare an 5” red wire. Tin one end and connect it to evelet #1 (forward) of the power supply board РС-19. (8). Connect the other end to lug A (triangle) of C11. (S-5). Be sure all these wires are soldered. Your SCA-606 1s now nearly half completed. The chassis should look much like the accompanying photograph. Set it aside for the present, and place the front panel before you. Wiring the Front Panel Mote that lugs on the controls (with the exception of the selector switch) are numbered in a clockwise direction when viewing the back of the control, and the right channel (red wires) is nearest the panel, and has the low lug numbers. The upper rows of lugs on the rocker switches (with the exception of MS) are for the left channel, In general you should try to keep components and wires which connect to the upper lugs above the switches, and those to the lower row below the switches. Keep green wires separated from red wires and cross them at right angles when necessary, Lo maintain maximum channel separation. Keep component leads short so that they will not interfere with the front preamplifier board when the panel is assembled to the main chassis, To enable you to trace wires on the pictorial diagram, some distortion of wire placement is necessary, so you should use the photograph of the front panel on the next page as a guide. lí Prepare a 14” red wire. Connect one end to BC lug #3. (8), Connecl the other end lo YC lug #2. (5), Zi ) Prepare a 2” red wire, Connect one end to YC lug #7. (8). Connect the other end to LS lug #6. ac Select a .022 mid capacitor and trim its leads to no more than 4”. Connect one end to LS lug #6. (5-2). Connect the other end to LS lug #5. 40 Select an 18,000 ohm resistor (brown-gray- orange). Connect one end to YC lug 71. Make sure it 15 clear of other switch lugs, and connect the other end to LS lug #5, trimming it as needed. (5-2). 50 )Prepare a 37 black wire, but strip 16” of insulation from one end. Feed the longer bared end through FS lug #1 from the top and connect it to FS lug #5. (5). Now solder lug #1 also, (8), Connect the other end to VC lug #1, 6. J) Prepare a 1%” black wire. Connect one end to YC lug #1, (5-3). Connect the other end to BC lug #1. ТО \Select a 27 pf disc capacitor. Connect one lead to BC lug #2. Connect the other lead to BC lug #1. BL Prepare a 3” red wire. Connect one end to BC lug #2. (8-2). Эс Prepare a 3" black wire. Connect one end to BC lug #1. (5-3). Position this wire past the top of the panel, along with the red wire from the previous step, and twist them together except for 15” at the free ends. 10{ )FPrepare a 115” green wire. Connect one end to BC lug #4. (8). Connect the other end to VC lug #5, (5). 11{ ¿Prepare another 116” green wire, Connect one end Lo YC lug 48. (5). Connect the other end to LS lug #3. 12( Select the remaming 022 mfd capacitor, Trim its leads to no more than 34” and connect one end to LS lug #3, (8-21, Connect the other end to LS lug #2. 13{ ¿Select the remaining 18,000 ohm resistor (brown- eray-orange). Connect one end to VC lug #4. Con- nect the other end to LS lug #2, (5-2). 141 154 161 171 187 194 201 1 227 23( a 261 )Prepare a 114” black wire, Connect one end to YC lug 4. (5-2), Connect the other end to BC lug #6. ¡Select the remaining 27 pf disc capacitor, Connect one end to BC lug #5. Connect the other end to BC lug #6. Prepare a 31%" green wire and a 314" black wire. Twist these together except for 15” at each end. Connect one end of the green wire to BC lug #5. (5-2). Connect the corresponding end of the black wire to BC lug 266. (5-3). ) Prepare a 67 red wire, Connect one end to MS lug #2. (8). Connect the other end to FS lug #8. Place this wire close to the panel and under LS, routing it as shown in the front panel photograph. \Select a 01 mfd non-dise capacitor, The disc capacitors are used elsewhere. Trim the leads to no more than 44” and connect one end to FS lug #7. Connect the other end to FS lug #8. (5-2). ¡»Select a 3300 pf (0033 mfd) capacitor, trim the leads to no more than 44” and connect one end to Fs lug #6. (51. Connect thé othér end to FS lug #7. )Prepare a 4” red wire, but strip 34” of insulation from one end. Feed the longer bared end through BS lug #7 from the bottom and across through the center of the switch to connect to BS lug 445, Keep the bare wire clear of adjacent lugs, and solder only BS lug #7 now. (8). Connect the other end to FS lug #7. (5-3). ) Prepare añother 4% red wire, Connect one end to OS lug #13. (5). Position this wire below the switch and against the panel, and connect it to BS lug #5. ) Prepare a 6144” red wire, but strip 15” of insulation from one end. Feed the longer bared end through BS lug #1 from the top, and connect it to BS lug #9. (5-3), Now also solder lug #1. (5). Keep thiz wire close to the panel and above control BC, and connect the other end to VC lug #3. (8). ) Prepare a 4%,” green wire. Connect one end to MS lug #5. (8). Connect the other end to FS lug #4. Place this wire along the top row of lugs and to the rear of LS, away from the red wires which should be crossed at right angles, ¡Select the remaining .01 mfd non-dise capacitor, and trim its leads to no more than 34”. Connect one end to FS lug #3. Connect the other end to FS lug #4. (8-2). Select the remaining 3300 pf capacitor, and trim its leads to no more than %”. Connect one end e у lug #2. (5). Connect the other end to FS ug Fd. ) Prepare a 314” green wire, but strip 34" of insulation from one end, Feed the longer bared end through BS lug #4 from the bottom, and across the top of the switch to connect to BS lug #2. Con- nect the other end to FS lug #3. (8-3). 21 Zi 28¢ 281 301 alí 321 dal ) Prepare a 414” creen wire. Connect one end to VC lug #6. (8), Connect the other end to BS lug #4. (5-3 One through wire=2). i Prepare a 4” green wire. Connect one end to 05 lug #14. (8). Tuck this wire under the switch and against the panel, and connect the other end to BS lug #2. Keep this wire at least 14" away from the red wire to OS wherever possible. ¡Select the 8200 ohm resistor (gray-red-red). Trim its leads to 14”, and connect one end to BS lug #6. (5). Connect the other end to BS lug #2. (5-3). Do not allow the resistor leads to touch the bare wire between lugs 5 and 7 of the switch, ) Prepare three red wires each 314” long. Connect these, and the following three red wires so that they point toward control BC as they come off the lugs to which they are soldered. Connect the first wire to DT lug #3. (8). Connect the second to DT lug #2. (8). Connect the third to DT lug #1. (51. ¡Prepare a 214” red wire. Connect it to DB lug #3. (5). | Prepare two 3” red wires. Connect the first to DE lug #2. (8). Connect the second to DB lug #1. (5). ) Prepare three 314" green wires. Connect the first to DT lug #4. (8). Connect the second to DT lug #5. (5). Connect the third Lo DT lug 76. (8). | | 341i dal HE ЭТ ) Prepare three 3" green wires. Connect the first to DB lug #4. (8). Connect the second to DBE lug £5. (8). Connect the third to DB lug #6. (5). } Select a 120 ohm resistor (brown-red-brown), and trim its leads to no more than 146”. Connect one lead to HP lug #5. (5). Connect the other lead to HP lug #6. If the resistor is placed against the jack, between the lugs, it will facilitate connecting additional wires later. iSelect the remaining 120 ohm resistor (brown-red- brown), and trim its leads to no more than 4%. Connect one lead to HP lug #3. (5). Connect the other lead to HP lug #2. ) Prepare a 115” red wire, but strip 34" of insulation from one end. Feed the longer bared end through OS lug #5 from the top and through the center of the switch to connect to OS lug #7. Solder both Ings, making sure the wire is clear of adjacent lugs. Connect the other end to HP lug #7. As long wires will be connected to the front panel in some of the following steps, be particularly careful of your eves when working on it. Also be careful that the lugs to which these wires are connected are not distorted or allowed to touch adjacent lugs through careless handling, 381 )Prepare a 12” red wire, Connect one end to HP lug #7. (5-2). 390 ) Prepare a $ green wire, but strip 34" of insulation from one end. Feed the longer bared end through OS lug #1 from the top, and connect it to OS lug #3. Solder both lugs, making sure the wire 18 clear of adjacent lugs. Position the wire over the top of the headphone jack, and connect the other end to HPF lug #1. 40( Prepare a 127 green wire. Connect one end to HP lug #1. (8-2). 41% ) Prepare a 12” black wire, but strip 1” of insulation from one end. Feed the longer bared end through 08 lug #12 from the bottom, through the center of the switch, and through OS lug #10 from the top, and finally over to OS lug #9. Solder all three lugs, keeping the wire clear of lug #11. Bend a hook in the far end of this wire for later identification. 42( Prepare an 11” black wire. Connect one end to OS lug 11. (5). 43( )Prepare a 12” red wire. Connect one end to O8 lug #6. (8), Bend a hook in the far end of this wire for later identification. 44( ) Prepare an 1115” green wire. Connect one end to 08 lug #2. (8). Bend a hook in the far end of this wire for later identification. 450 1 Select one of the 02 mfd disc capacitors. Trim each lead to 3”, and slide a 14" piece of insulating sleeving over each lead. Connect one lead to PS lug #2 and the other to PS lug #3. 46( |) Select the remaining (2 capacitor. Trim its leads tao 34”. and slide a 14” piece of insulating sleeving aver each lead, Connect one lead to PS lug #5, and the other to PS lug #6. Place both capacitors along- gide the switch frame, one on each side, 47( Prepare four wires each 17” long: two blacks and [wo reds. Connect one end of each of them to switch PS as follows: A red wire to lug #3. (5-2). A black wire to Jue 42, (8-2). A red wire to lug #6. (8-21. A black wire to lug #5. (8-2). 48( J Prepare an 187 green wire. Connect one end to PS lug #4. (5). 49{ Twist together the green wire from PS lug 4 with the black wire from lug 2 and the red wire from lug 3 throughout their length except for one inch at the free end. Twist them uniformly, so they remain nearly equal in length 500 Twist together the black wire from PS lug 5 and the red wire from lug 6 except for one inch at the free end. You will next wire the selector switch. Be very careful of this, for the phenolic wafers are relatively delicate, and you must be careful that the long wires do not put undue stress on them. Be careful that you do no! twist the lugs on the rivets which hold them, as the rotational “timing” of the switch contacts is critical, and twisting the lugs could result in malfunction. The switch lags are numbered clockwise starting at the top of the switch, when looking at it from the front of the panel, Lug #9 on both wafers (which are identical) has two Independent sections. When connections are called for here, they will specify the forward or back portion of the lug. In all other positions where a double lug appears, the two sections are to be soldered together when the connection is made. Do not allow excess solder or rosin flux lo flow down the lugs onto the switch rotor contact area, or malfunction may resull. 510 Install the selector switch in location SS. Make sure the locating tab engages the small hole in the front panel and fasten the switch with a 24" nut. The next 17 steps refer to wiring the front switch wafer, which 15 the one nearest the panel. 520 Select one of the 10,000 ohm resistors (brown- black-orange) and trim each lead to 3%”. Connect one end to MS lug #1. (S). Connect the other end to 55 lug +9 (forward), keeping the resistor in front of the switch wafer. 030 select another 10,000 ohm resistor (brown-black- orange). (Connect one end to MS lug #3. (5). Keep the resistor in front of the wafer, and connect the other end to SS lug #11. 047 Connect a short piece of wire from SS lug #11 to 85 lug #12. (5). Also solder lug #11. (5-2). 300 Prepare a 3" red wire. Connect one end to SS lug #2. (5). Be sure both lugs are soldered together, 60 | Select one of the 5 mid capacitors. Do not trim these leads as nearly their full length will be needed. Note that the positive end is marked with a (+) sign, Feed the lead from the negative end through 55 lug 34, and connect it to 55 lug #3. (5). Also solder lug #4. (51. 570 ) Prepare а 18%” red wire. Connect one end to 85 lug #5. (5), 58( Prepare an 1145” red wire. Connect one end to SS lug #6. (5). Be sure the two lugs are soldered together. This wire should point toward lug 7 when it is soldered. 590 ) Prepare a 1034" green wire. Connect one end to SS lug 7, (3). 600 ) Prepare an 1114” black wire. Connect one end to 55 lug #9 (back). 61( ) Carefully twist together the long red, green and black wires from the previous steps throughout their length except for one inch at the free end. This group should come off the side of the switch between lugs 7 and 8. The black wire has not vet been soldered. 620 J Prepare a 12” red wire, Connect one end to 55 lug #8. (8). Solder both lugs together. Push the twisted group toward the panel first, to make it easier to connect this wire, and the next ones. Watch that the lugs are not twisted in the process. 23 63( ) Prepare a 1214” green wire. Connect one end to SS lug #9 (forward). (5-2). 64( Prepare a 3%" black wire. Thread it through the switch above the center shaft, and connect one end to SS lug #9 (back). 65( ) Prepare a 13” black wire. Connect one end to 55 lug #9 (back), (5-3). 66( ) Prepare only one end of à 13” red wire. Do not re move the insulation from the other end, as this will serve for identification later. Connect the bared end to 55 lug #10, (5). 67( Prepare only one end of à 1415” green wire. Con- nect the bared end to 58 lug #1. (5). This wire should pass lugs 12 and 11 as it is brought around to the side of the wafer. 68( Carefully twist together the five long wires from the previous steps throughout their length. This group should come off the switch at lug 9. The next 17 steps refer to wiring the rear switch wafer. 690 Select another of the 10,000 ohm resistors (brown- black-orange). Connect one end to MS lug #6. (54. Connect the other end to 35 lug #11. TOC \Connect a short piece of wire from 55 lug #11 to SS lug #12. (5). Also solder lug #11. (5-2). 710 Select the remaining 10,000 ohm resistor (brown- black-orange). Connect one end to MS lug #4. (8). Connect the other end to SS lug #9 (forward), 72( ‘Prepare a 3” green wire. Connect one end to 53 lug #2. (5). 73( Select the remaining 5 mid capacitor. Keep the leads full length. Feed the negative end through 55 Jug #4 and connect it to SS lug #3. (5). Also solder lug #4. (5). T4{ Prepare a 124" green wire. Connect one end to 55 lug #5. (5). 75( J Prepare a 9%” red wire. Connect one end to 55 lug #6. (8). This wire should point toward lug 7 when it is soldered, 76( Prepare a 9° green wire. Connect one end to 85 lug #7. (8). 770 Prepare a 9” black wire. Connect one end to 55 lug #9 (back). 780 Carefully twist together the long red, green and black wires throughout their length except for one inch at the free end. This group should come off the side of the switch at lug 8. The black wire is not vet soldered. 79( Prepare a 94” red wire. Connect one end to 55 lug #8. (5). Push the previous group forward to make connection of this wire easier, A0( Prepare a 94,” green wire. Connect one end to 55 lug #9 (forward). (5-2). 810 Prepare a 314” black wire. Connect one end to 55 lug #9 (back). This wire should point toward lug 3. 82( Prepare a 10" black wire. Connect one end to 55 lug 29 hack). (5-3), 830 Prepare only one end of a 10” red wire, Connect the bared end to 59 lug 710. (8). B40 ) Prepare only one end of an 11” green wire. Connect the bared end to 88 lug #1. (8). This wire should pass lugs 12 and 11. 850 Carefully twist together the five long wires throughout their length: This group should come off the switch at lug 10, Final Assembly Set the front panel aside and prepare to wire the back panel. In the following steps reference will sometimes be made to pairs of short lugs on the input socket strips. These are located between the long lugs of the numbered sockets. These short lugs will be identified by a dashed number, as [#1-2], and connections are made to both, soldering them together when called for. The long lugs will be identified by a single number. 10 ¿Prepare two 2" black wires. Connect one end of the first wire to the pair of short socket lugs #5-6. Con- nect the other end of this wire to short lugs #44. (5). 2( Connect one end of the second 2” black wire to short lugs #11-12. Connect the other end to short lugs 49-10. (5). 3( Select one of the .01 disc capacitors and trim the leads to no more than 34”, Connect one lead to short lugs #1-2. Connect the other lead to the adjacent ground lug on the upper bolt. (5). 4( Select the remaining .01 disc capacitor and trim the leads to no more than 34". Connect one lead to short lugs #7-8. Connect the other lead to the adjacent ground lug on the upper left bolt. (8). 5( Prepare a 3” black wire. Connect one end to output lug #8, (8). Connect the other end to output lug 75. 60 Select the large 10 ohm, 10 watt resistor. Trim its leads to no more than 34”, Connect one lead to output lus #5. (5-2). Connect the other lead to output lug #1. 70 Prepare a 3” black wire. Connect one end to output lug #1. (8-2). Connect the other end to output lug #4. 80 Separate the two conductors at the end of the line cord for about two inches, and mark the cord with a pencil 314" from the end. Strip 14” of insulation from both wires if necessary, twist together the separate strands of each wire, and “tin” the end to prevent fraying, Bend the cord sharply back on itself at the pencil mark, and squeeze the bend with pliers to form a sharp “Y”. Install the strain relief 9 at the V as shown in detail B, with the small end of the strain relief nearest the bared wire ends. Use pliers to squeeze the two halves of the strain relief together around the wire, to partially shape the wire before insertion. Then grasp only the larger diameter part of the relief with the tips of the pliers as shown, squeeze it fully closed, and insert the bared wire ends and the strain relief from outside the back panel through the remaining hole in the panel. The strain relief will snap into its locked position when fully inserted. Detail B ) Connect one of the two conductors of the line cord to AC outlet lug #2. Connect the other conductor to AC outlet lug #1. Set the back panel aside and return to the main chassis, 104 11( 12( 13% 14( 15( Install the front panel with only two of the brass shéet metal screws in the corner holes only. Tilt the panel out for working. Place the 6 wires from OS and HP against the chassis between the power transformer and PC-19. The twisted groups of wires stay outside the edges of the chassis for now, ) Unhook the wire from the clamp of CTR (the front capacitor) and connect the free end to HP lug #6. Loosen the clamp so you can take up slack in the coil by rotating the capacitor. ) Prepare a 7” red wire. Connect one end to HP lug #6. (8-3). This wire can be wrapped around the lug if it will not fit through the hole in the lug. Make sure all connections are soldered. )Unhook the end of the coil around CTL from the edge of the chassis and connect the free end to HP lug #2. Loosen the clamp to take up the slack in the coil, ) Prepare a 13” green wire. Connect one end to HP lug #2. (8-3). J As you tilt the front panel into its upright position, twist the capacitors CTL and CTR clockwise to keep the coils tight. Watch the short wires from the selector switch lugs 2, 4, 5 and 9 of each wafer. Those from the rear wafer go between the two preamplifier boards. Install two more brass sheet metal screws to hold the front panel rigidly. Tighten the clamps of C7L and CTR, making sure the capacitors are seated firmly to the chassis. —— 20 16( Select the long black wire (from OS lug 12) which has the hook in it and connect it up from underneath one of the ground lugs at the base of PC-19, (5-5): Make sure all of these wires to both ground lugs are well soldered, 174 Install the back panel with only two of the brass sheet metal screws in the corner holes, and tilt the panel out for working. 18( Select the long red wire with the hook in it (from OS lug 6) and connect it to output lug #6. (5). 19( Select the long green wire with the hook in it (from OS lug 2) and connect it to output lug #7. (8). ) Twist together the two red leads from the power transformer, If you wish, the transformer leads may be shortened for neatness, but remember that the transformer warranty is voided if the leads have been cut too short for re-use. Be sure the bared ends are tinned, Connect one of the red leads to eyelet #9 of PC-19. (8). There is less risk of damaging the diodes on the board with excessive heat if the iron heats the evelets from the rear of the board while the lead is inserted from the front. Make sure that all strands of each lead are soldered to the evelet. Connect the other red lead lo eyelet #8 of PC-19. (8). These red wires are on top ol the three wires just connected. The remaining three go on top of the red wires, and will be connected later. 21( Select the black and red twisted pair from the power switch PS, place it around the power transformer and between the two AC outlets on the back panel. Connect the black wire to AC lug #3. Connect the red wire to AC lug #1. (8-27. 22( ) Select the black, red and green twisted group from PS, and place it around the power transformer. Connect the black wire to AC lug #4. Connect the red wire to AC lug #2. (5-2). Do not connect the green wire yet. The next 5 steps describe 120 volt AC wiring for the U.S. and Canada, Page 32 describes alternate wiring for other line voltages, If one of these is chosen, complete that wiring now in place of the following 5 steps. Transformer leads can be shortened for neatness, so long as no alternate use is likely. Be certain all strands of a lead are twisted together and soldered to the lugs. 23( ) Connect the green wire from the power switch to the top (side) lug £1 of the fuse holder. 24( ) Twist together the black and the black-white power transformer leads, and connect them both to the top (side) lug #1 of the fuse holder, (5-3). NOTE: In Canada the fuse holder cap must be cemented in place, and a separate “pigtail” fuse installed, so solder this connection, and go to the NOTE in the next step. 25( Prepare a l%” black wire. Connect ône end to AC lug #4. (8-2). Connect the other end to tip lug #2 of the fuse holder, (8), NOTE: In Canada select the pigtail fuse, trim its leads to 34", and slide a 14” piece of insulating sleeving over each lead. Connect one lead to side lug #1 of the fuse holder. (5-4), Connect the other lead to AC outlet lug #4. (5-2). See separate pictorial diagram. 25 261 27 Z8( 29( $01 311 321 Hal 341 dot 36( ail \ Twist together thé violet and the violet-white transformer leads, and connect them both to AC lug #3. (5-3). \ Twist together the green and the vellow transformer leads. Connect the green lead to TS lug #3. (8), Connect the vellow lead to TS lug #1. (5). Select the twisted group of five wires from the selector switch front wafer, and connect them to the input sockets as follows: The stripped red wire to lug #9. %8), The stripped green wire to lug #10. (85). Strip '47 of insulation from the red and green wires remaining, Connect the red wire to lug #11. (8). The black wire to shor! lugs #11-12. (8-2). The green wire to lug #12. (5). Note the photograph on the following page which shows the placement of this group, and the other three groups from the selector switch, ) Select the group of three twisted wires from the front wafer, and connect them to the input sockets as follows: The black wire to shor! lugs #T-8. (5-2). The red wire to lug #8 (5). The green wire to lug #7. (81. ) Lift the twisted groups from the power switch near the top of the transformer so they will not be pinched, and tilt the back panel upright, Install two more brass sheet metal screws to secure the panel to the chassis, ¡Select the twisted group of five wires from the selector switch rear wafer, and connect them to the input sockets as follows: The stripped red wire to lug #3. (5). The stripped green wire to lug #4. (S), Strip 14” of insulation from the red and green wires remaining, Connect the red wire to lug #5. (5), The black wire to short lugs #5-6. (5-2). The green wire to lug #6. (5). ) Select the group of three twisted wires from the rear wafer, and connect them to the inpul sockels as follows: The black wire to short lugs #1-2, (8-2). The red wire to lug #2. (5). The green wire to lug #1. (8). Select the remaining long black wire from OS lug 11 and connect it to output hug #4. (5-2). 1Select the long green wire from HP lug 1 and connect it to output lug #3. (5). )Select the long red wire from HP lug 7 and connect it to output lug #2. (8). "Tin" the ends of all the wires on the chassis which are still unconnected, as this will simplify soldering them to the evelets. Don't forget the short wires from lug 5 of each selector switch wafer. Do not tin the lead of the 5 mfd capacitor on the rear wafer of the selector switch. ) Connect the red wire from HP lug 6 lo eyelet #1 of the front amplifier board. (8). Place it down toward the chassis. Зе ad 41¢ 421 431 441 45 461 47 | 451 49( al ¡Connect the green wire from HP lug 2 to eyelet #1 of the rear amplifier board. (8S), Place this wire toward the chassis and around the right heat sink. ) Connect the short green wire from 8S rear wafor lug 9 to eyelet #1 (forward) of the rear preamplifier board. (5). ) Connect the black wire from SS rear wafer lug 9 (back) to evelet #2 (forward) of the rear preamplifier board. (5). ) Connect the green wire from 85 rear wafer lug 2 to evyelet #5 (forward) of the rear preamplifier board. (5). \Strip a 1” piece of insulation from the black wire, and slip this insulation over the positive lead of the 65 mid capacitor from 55 rear wafer lug 4, Tin the end of the capacitor lead and connect it to eyelet #6 of the rear preamplifier board. (5). | Connect the short red wire from SS front wafer lug 5 to eyelet #1 (forward) of the front board, (8). } Connect the black wire from SS front wafer lug 9 {back} through the center of the switch to evelet #2 of the front board. (8). ) Connect the red wire from SS front wafer lug 2 to eyelet #5 of the front board, (8). ) Connect the positive lead of the 5 mid capacitor from 85 front wafer lug 4 to eyelet #6 of the front board. (S). Make sure the bare leads cannot touch the control. )Select the short red and black twisted pair from BC, keep it above the green and black pair, and connect the red wire to evelet #9 of the front board. (5), Connect the black wire to evelet #10. (8). 1 Select the green and black twisted pair from BC, and keep it reasonably clear of the red and black pair. Connect the green wire to eyelet 49 of the rear preamplifier board. (8). Connect the black wire to eyelet #10. (5). ¡The six red wires of the DB and DT controls are connected to the front board as follows: DE lug 3 to evelet #13. (8). DB lug 2 to evelet #14. (3). DB lug 1 to eyelet #15. (8). DT lug 3 to eyelet #16. (5). DT lug 2 to evelet 417, (5). DT lug 1 to eyelet #18. (5). )The six green wires of the DB and DT controls are connected to the rear preamplifier board as follows: DB lug 6 to evelet #13. (5). DB lug 5 to evelet #14. (5). DB lug 4 to eyelet #15. (5). DT lug 6 to evelet 4416. (5). DT lug 5 to evelet #17, (8). DT lug 4 to evelet #18. (8). 51( Prepare a 7” red wire. Tin both ends, and connect one end to evelet #19 (hack) of the front preamplifier board. (5). Connect the other end to eyelet #12 (forward) of the front PC-18 amplifier board. (5). 520 JPrepare a 4%” green wire. Tin both ends, and connect one end to evelet #19 (back) of the rear preamplifier board, (5). Connect the other end to eyelet #12 (forward) of the rear PC-18 amplifier board. (5), 53( JPrepare a 7” green wire. Tin one end, and connect it to evelet #7 (back) of the rear PC-18 amplifier board. (5). Connect the other end to the red lug of CTL. (8). 54( Prepare a 7” red wire. Tin one end, and connect it to evelet #7 (forward) of the front PC-18 amplifier board. (5). Connect the other end to the red lug of CTR. (5). This completes the wiring of your SCA-50Q. Check to see that there are no unattached wires and no unsoldered connections. Clip off any excessive stubs of wires to make a neat job. Check to make sure that the connections to each evelet on the circuit boards show a smooth flow of solder from the wire to the circuitry. There are no connections to evelets 7 and 8 of the preamplifier boards. If the unit was wired for 120 volt use, there will be no connections to lugs 2 and 4 of the rear panel lug terminal strip. Lug 2 is used only if a special grounded power cord is necessary. Mow turn the chassis over and shake out any hits of wire or solder. Check the twisted wires from the power switch to make sure they are not pinched by the chassis. Position the twisted groups of wires from the selector switch as shown in the photograph below, In particular, the groups from the rear wafer should be separated from the front wafer groups to preserve maximum channel separation. Be surg none of the leads from the front panel touch the front preamplifier board circuitry. Check the resistor nearest the ground lugs on PC-19 to be certain that its lower lead cannot touch the chassis. Algo make sure that no connecting wires are likely to come into contact with any of the power resistors on PC-19, as these will get quite hot in normal operation, Check to see that red and green wires do not closely parallel each pther unless they are twisted groups, or are connected to the same point. The parallel wires from OS and HF on the front panel to the outputs on the back panel do not matter. For best channel separation red and green wires should cross at right angles to each other. General placement of wires should conform more closely to the photograph than to the pictorial diagram, which must necessarily be distorted to enable you to trace each wire, Make sure that wires which connect to the center lugs of C11 do not touch the outer ground lugs of the capacitor. Check the power switch to make sure there is no possibility of shorted connections between the lugs. The lead of the 5 mfd capacitor from the rear 83 wafer should not be able to touch the bare wires between the preamplifier boards. The wires to the solder (ground) lugs on the heat sinks should not be able to touch the heat sinks or the cover when it is installed. 550 Insert a brass sheet metal screw into the back panel hole marked “GND”. This is the point to which separate ground wires from the record player, etc. may be connected. 56( >) Insert the fuse into the fuse holder. (Skip in Canada). 57( Install the front plate, securing it with à #4" nut on shafts 85, BC and DT. Jack HP should protrude very slightly to avoid scarring the panel when plugs are inserted. If the plate does not seat properly, vou can loosen the mounting hardware and shift a switch or control slightly. 580 1The Allen head set screws are in a bag with an Allen wrench. Insert a screw into each knob, and position the large knobs on shafts 858 and VC so that the set screw engages the flat on the shaft. The small knobs are positioned on the other shafts so that rotation is symmetrical to either side from top center. 59( Install the black thumb screws in the outer positions (marked “common”! of the output terminal strips on the back panel. If they do nol easily screw tightly to the panel, you should bend the small tab on the outside of the strip out of the way. Install the gold finish thumb screws in the remaining output terminals, and make sure they thread in fully. 60% }Slide the cover on, and secure it with 5 brass sheet metal screws. The fifth screws into the top center of the back panel. If vou have not already done so, read the “Operating In- structions” before turning the amplifier on. Remember to connect the input and output leads to the amplifier before the power is turned on. 27 IN CASE OF DIFFICULTY Your SCA-80 should function properly after assembly, and you can usually assume that if it functions to your satisfaction, it is meeting all of its specifications. Some- times a wiring error, poor solder connection, or defective component may require trouble-shooting. Because 909% of the difficulties which are encountered in kit-built units can be attributed to incorrect wiring or a poor solder connection, it is strongly recommended that you ask someone else to check your wiring against the pictorial diagram, as frequently one person will make the same error repeatedly. The SCA-80 has been carefully designed to provide exceptional accessibility for the serviceman, The average kit-builder should confine his servicing to the basic supg- gestions given here, after checking to make sure the fuse is intact. Audio transistors, unlike tubes, cannot be easily checked locally for any other than gross defects, and even this should be left to the qualified technician. For this reason your SCA-80 is considered to have “no user- serviceable parts inside.” Each of the 4 amplifier and preamplifier circuit boards, and all 4 power transistors have been in-circuit tested to assure that they meet specifications prior to shipment, so routine trouble-shooting can eliminate these as the sowrce of the trouble, although they could have been subsequently damaged. There are certain general précautions to be observed in servicing any transistorized equipment: 1. Never make circuit changes (connections or disconnec- tions) of any kind when the amplifier is turned on, 2. Be particularly careful not to short any transistor leads to each other or to the chassis when the power is on, 3. When using test equipment, you must avoid transient voltage peaks and excessive test voltages. 4. Exercise caution when soldering and unsoldering transistor and diode leads to avoid excessive heat. Check the connections at each evelet along the edge of the circuit boards. There must be a smooth flow of solder from the wire, across the eyelet, onto the circuit board. If in doubt, reheat the connection and add more solder if necessary, but a lot of solder can conceal a poor connection. Look for flecks or splashes of solder on the circuit side of the board which may be causing unwanted connections. Make sure the large capacitors are seated firmly to the chassis, so that their lugs cannot contact the cover, Check the selector switch to make sure that the two wafers are aligned, and that double lugs are soldered together. The #9 lug has separate front and rear sections with independent connections, Make sure the rear portion of this lug has not been twisted on the wafer. If difficulty is in the input to one channel, the selector switch deserves special attention, If you have no signal at all, check the Monitor and Speakers switches, A systematic checking procedure will enable vou to localize the problem area. A problem common to both channels is cause to suspect the power supply section, comprised of the line cord, power switch, fuse, power transformer, PC-19, C2 and C11, If a VTVM (or TYM) is available, a voltage variation of more than 10% will help to pinpoint a problem. A higher than normal voltage at the collector of one of the transistors, for example, is possibly indicative that it is open and requires replacement. Voltages at the transistor leads, where shown, may vary + 20 % and still be normal. 26 Power Supply Measuring the AU voltage between eyelets 5 and 9 on PC-19 will check the power transformer. A defective rectifier or poor solder connection on the rectifier diode bridge may cause the power transformer to emit an audible mechanical vibration. The IMC voltage measured across 29 will be about 75 volts if the rectifier diodes are functioning properly. The most likely cause for a blown fuse will be a shorted rectifier diode. You may be able to isolate a fault in one power amplifier channel by removing the wire to one of the amplifier heat sinks from the red lug of C9, If the other channel then functions normally, the disconnected channel is suspect. Similarly, low voltage on a section of the C11 capacitor may indicate excessive current drain from one or the other channel, and disconnecting one board may localize the problem. Power Amplifiers lt is possible to operate the SCA-80 monophonically in the event of difficulty with one power amplifier channel The problem heat sink and circuit board assembly then may be removed from the circuit and returned to Dynaco for test and service by unsoldering 10 wires. For safety, these should be disconnected at the “far end” so that no unattached wires will ba left in the amplifier. If you wish, the wires may be unsoldered from the assembly, and each insulated with electrical tape. Do not return the circuit board alone unless vou are certain that the output transistors and the power supply resistors R16 and R17 are performing normally and that the fault has nol affected the preamplifier section. It is normal for the R16 and R17 resistors to run warm—in fact, they put out most of the heat from a normally functioning amplifier at average power levels—but if one runs much hotter than the other in the same channel, it indicates output transistor or diode failure. Excessive discoloration of any resistor also is a sign that it should be replaced. When packing a circuit board and/or heat sink, be sure the packing adequately protects the board from damage, and protects the transistors so that their leads are not bend or crushed. Because the assembly is hight in weight, it may be shipped by air if desired, saving a large part of the normal service delay time. Preamplifiers—Tone Controls A problem in the preamplifier section should include careful checking of the selector swilch because it inter- connects the low level preamp stages with the tone control sections, A svstematic check can localize a problem in one channel to the preamp or tone control sections. For example, if there ig insufficient oulpul on the left channel phono input, see if this channel operates properly through the tuner input. If it does, the problem is in the low level section of the left channel, If there is no output from either left channel input, then the low level section can be tested with some ingenuity. If you realize that the “Tape Out” signal is available before the volume and tone controls, vou can connect the left channel tape output into the identical input on the right channel as the program source vou are using on the left channel. If vou then have suitable signal level, the trouble lies in the left tone control section. You can also interchange channels internally by connecting the output of the preamplifier (evelet 19) to the opposite power amplifier input (eyelet 12). Hum and Moise The SCA-80 is inherently hum-free, and if any is de- tected, the inputs should first be unplugged. If there is no hum with the cables removed al the same volume setting as when the hum was noted, the problem must be corrected in the associated equipment. Sometimes the addition of a ground wire from the record player chassis or tone arm, or from a tape recorder, to the SCA-80 Gnd screw will eliminate hum, but it is generally advisable to use the fewest ground wires which achieve the desired result to avold ground loops. Some phono cartridges are more hum susceptible than others, and may not be suitable in certain installations where they are close to power transformers, AC power lines, ete. Sometimes simply placing the record player so that the cartridge is not so near any power transformer may alleviate the hum, Hum which is common lo both channels of the SCA-80 ilself is almost certainly in the power supply. Be sure the cover is in place, however, for external fields will affect the results. When there are no cables connected to the low level inputs, it is normal to have a high hiss level at high volume settings on Phono and Special. With sources connected, hiss should be inaudible at normally used volume settings, though some hiss may be evident at much higher settings of the volume control. Beyond the most rudimentary checks, servicing of transistorized equipment should be left to the qualified technician. The SCA-80 needs no maintenance in normal use, and there are no adjustments required during the life of the amplifier, Improper servicing can impair its performance or damage it, so it is very important that the technician familiarize himself with the Circuit Description and with the Service Information which follows, before proceeding. Unless you are confident thal a local repairman has the specialized knowledge and equipment for servicing high quality solid state audio equipment, factory service is strongly recommended, SERVICE INFORMATION FOR THE TECHNICIAN (FOR QUALIFIED PERSONNEL ONLY) Before servicing the SCA-80, be sure to read the circuit description in the front of this manual, as well as the pre- ceding section, for some of the amplifier’s unique features may not be immediately apparent when examining this essentially simple circuit, A systematic check of voltages and signal paths, based on an understanding of the circuit, will lead to rapid diagnosis. Preamplifiers—Tone Controls The voltage chart does not specify voltages on the eyelets of the preamplifier boards because they are not signifi. cant, and may vary widely with individual transistors, If the problem is one of little or no signal, then simple signal tracing, following the signal path carefully and injecting some hum by touching each connection in turn is advisable. If there is a point after which hum occurs, and before which there is silence, vou have located the trouble area. The tone control potentiometers are of unusual construction, and cannot be measured by the usual continuity check. The bass control has a dual wiper, and the treble control has a discontinuous element. Objectionable hiss gt normal listening levels may be caused by a faulty Q7 transistor, unless it occurs on both channels, If there is hiss on both low level inputs of one channel, you can interchange Q7 with one of the other transistors, but return them to their original positions if this is not the trouble. The transistors in the tone control stages are not likely to be a source of objectionable hiss. Amplifiers The left and right audio channels are electrically identical. Each amplifier has two basic sections. The direct-coupled pair Q1 and Q2 is the Class A amplifier-driver with a DC feedback loop from the second emitter to the input base. Audio signals at the input base of Q1 are amplified and appear at the collector of Q2 to drive the four-transistor Class B power output section. (33 and Q4 are a complementary-symmetry driver directly coupled to Qb and Q6 output power transistors. The Class B section provides a power gain, but no voltage gain. The input junction of Q3 and Q4, and the output junction of Q5 and Q6 swing together through the signal evcle. The ability of the output junction to follow the input junction (and the consequent linearity of this section) depends on the feedback path from the collector of Q6 Lo the emitter of (M4. Vanations al (4 emitter compared to its base potential will create a corrective signal for Q6, which makes the output follow the input. Diodes D2 and D3 are in this feedback path, in a direction which would not be conductive (breaking the febdback path) were it not for the forced current through bleeder resistors 16 and H17. When the current in Q4 reaches that in R16 and R17, the diodes ID2 and D3 no longer con- duct, and the feedback path is broken. Simultaneously D1 starts conducting and makes a short circuit between the input of 3 and Q4, and the output of Q5 and Q6. Thus when the current demand in the feedback loop exceeds the limit determined by the bleeder resistors, the ability of the circuit to drive is restricted, and excessive currents cannot be induced in Q5 and Q6. The action of DI short circuits the drive from QZ, reducing the drive until the cause of the high current demand is corrected. Thus an excessive drive signal, or too heavy a load on the output, which would require excessive current, switches the circuit to à configuration which prevents damaging current flow through the output and driver transistors. Trouble-shooting the amplifiers Any signs of scorched resistors or wire should be a basis for further investigation. If either R13 or R14 is burned, or smokes when the amplifier is on, then at least one of the transistors Q5 or Q6 and possibly (3 ог СМ: Лав been damaged, and replacement will be required. It must be empha- sizod that if one of the transistors in the Class B section QS, 4, Q5, Q6) is defective, the other three must be tested before proceeding further to avoid possible repetitive breakdown, Resistors R16 and R17 on the power supply bourd normally get hot because of the reference bleed current. lf only one of the pair is hot, Q5 or 6 may be shorted, or D2 or DJ may be open. Heat observed under no signal conditions indicates excessive bias drop or oscil- lation (either internal, or from the source). The voltage at the positive terminal of C7 should be about 36 volts (one half of the supply voltage). If this voltage is far off value, this can be a sign of trouble in one or more of the Class B transistors, and all should be checked. 29 If the voltage at the input bases of Q3 and Q4 is signifi- cantly different {more than 1.5 volts) from the voltage а! C7, the voltage at the other end of C4 should be checked to determine if something is wrong in the Class A section, (31 and QZ. A fault in either of these transistors can change the voltage at the collector of Q2 (input of C4), and this can be reflected in an incorrect potential at the bases of Q5 and Q4, which is further reflected in the junction of Q5 and 96 (the positive terminal of C7). Voltages al either end of C4 may be inter-related when Cd is in the circuit. If one end of C4 is lifted, the voltage deviations from normal at either end will indicate whether a fault lies before or after C4. It is unlikely that all voltages in the audio section are correct if there is no sipnal, However, if this condition occurs, it 1s most likely an open input capacitor Cl, or coupling capacitors C4 or C7, or a shorted C2. A signal which has some distortion, or is limited in power output, is more difficult to diagnose. See the section relat- ing to performance tests. This requires a distortion ana- Iyzer and an oscilloscope to check the signal, and then routine signal tracing should locate the fault. Checking transistors An ohmmeter 1s all that is required to locate a transistor which has failed. Small transistors must be removed from the circuit board for test. The power transistors need not be removed from the heat sinks, but the wires to their terminals must be detached for measuring. All transistors can be considered (for this test procedure) to be two diodes connected in series with common elements tied together, The junction point represents the base of the transistor, The identification of the larger power transistors is shown in the photograph of each heat sink. The smaller ones, observed from the bottom, have the collector, base and emitter arranged counter-clockwise, with the collector attached directly to the case. With one ohmmeter probe connected to the base, the other probe should be touched to the collector and emitter in turn. Readings from the base to the collector, and from the base to the emitter should be similar. With one orientation of the probes, there should be a high resistance reading (almost an open circuit), When the polarity of the probes is reversed, there should be a relatively low reading. The high reading will appear with one orientation of the probes for a pnp transistor, and with the opposite orientation for an npn transistor. Then the ohmmeter should be connected from collector to emitter, and a high resistance {almost open circuit) should be read, regardless of the orientation of the probes. If all of these qualifications are met, the transistor does not exhibit any gross defects Qualitative evaluation of acceptable transistors requires equipment beyond the scope of local service facilities. In similar fashion, diodes can be checked by verifying that they have a high resistance in one direction, and low resistance in the other, When replacing transistors, the small ones with the finned radiators should have the radiators transferred to the replacement. The silicon grease between transistor and radiator should be transferred to the new transistor, Be careful to insert the leads into the proper eyelets. Do not use excessive heat on the leads—let the heat go to the eyelet instead. When replacing the power transistors on the heat sinks, maintain the mica insulator between the transistor and the heat sink. Spread some of the silicon grease, which is a heat transfer compound, between the mica insulator and the transistor, as well as between the heat sink $0 and the insulator. Be sure to use the nylon insulators around the mounting screws. When making replacements, standard types can be used provided they are ecreened beyond the manufacturers routine specifications. This is necessary because transistors of a given type vary far more widely than do tubes. The requirements for each transistor are given in the parts list with the schematic diagram. No screening will be necessary for transistors obtained from Dynaco if the application (Q-number) or the Dynaco part number is specified. If emergency needs require substitution of an unscreened tran- gigtor, the audio circuits will function but the effectiveness of the protective circuitry may be somewhat reduced. The Dynaco audio circuit has been designed so that no matching of transistors is required. While the parts list does not show all of the possible transistor options, under no circumstances should unlisted transistors be used unless factory-approved in advance. SERVICE POLICY AND LIMITED WARRANTY The SCA-800 has been designed to provide reliable; trouble-free operation for a long period of time when it has been properly assembled and installed, It incorporates un- precedented circuil protection against failure caused by abnormal operation. So conservative is its design that at will deliver specified performance with the maximum variations in AC line voltage (110 to 130) permitted in normal vise. Despite these precautions, service may sometimes he needed, and you should be sure to return the warranty card promptly to validate your warranty, Dynaco maintains a complete factory test and repair facility for which no return authorization is required. Unless specifically authorized in advance by the factory, Dynaco cannot assume any respon- gibility for local service charges. In addition to the factory, independent authorized service facilities are available in several U.S. cilies and in Canada, Write Dynacoó for the one nearest you. À factory assembled SCA-50G/A is warranted to be free of defects in materials and workmanship for a period of one year from the date of purchase, During the warranty period, no charge will be made for testing or servicing any defective factory assembled SCA-800/A returned to Dynaco. All parts used in an SCA-BOG) kit are warranted to be free of manufacturing defects for one year from the date of purchase. Defective parts will be replaced promptly at no charge upon receipt for inspection at the factory, After the warranty period has passed, Dynaco will supply any non- standard parts at net prices. Standard parts can generally be obtained from a local electronics supply store, The warranty does not apply to other than the original purchaser, nor to units which have been subjected to ne- elect, abuse, misuse or accident. If you suspect a defect in the power transformer, the leads must be unsoldered, not cut for its return. The warranty on the transformer is void if the leads have been cut too short for re-use, If the kit has been completely assembled, vet does not function properly, or if difficulty develops after some use, Dynaco will service the SCA-800 for a nominal charge. After one year, assembled units and kits are also subject to the same charge, plus the cost of parts. As described elsewhere in this manual, the power amplifier circuit board assembly and related heat sink can be removed and returned for service af the factory, The labor charge for each assembly will be nominal, plus the cost of out-of-warranty parts. The service charge for two such assemblies returned together will not exceed the service cost for a complete amplifier. Unce a complete SCA-806) has been serviced by Dynaco for which a regular service fee was charged, a 90 day service warranty 15 given. No service warranty can be extended for individual circuit board assemblies. Factory service is not available for kits which are incom- pletely wired, or kits wired with other than rosin core solder, or units physically or electrically modified or used contrary to the Operating Instructions, without prior factory authorization. Technical assistance which may facilitate local diagnosis or service iz available at no charge. Such assistance depends entirely on your description of the difficulty and any tests performed. Be as complete as possible. The serial number of the amplifier which 18 on the cover of this manual should be mentioned in all correspondence, and whenever a part or the unit is returned to the factory. When shipping the amplifier to Dynaco Ine. for service, include a note listing the symptoms, the name and address of the sender, and the serial number of the unit. Pack the unit securely to withstand the abuses of handling in transit. The complete original packing, if properly used, and in cool condition, will be sufficient for Express or URS. shipment, PARCEL POST IS NOT A SAFE METHOD OF SHIPMENT, AND SHOULD NOT BE USED. If no alternative iz available, the unit must be double-packed with substantial packing between the cartons, and tt must be insured. Shipments should be made by insured prepaid Express or Motor Freight, Serviced units will be returned by Express or United Parcel Service, collect for all transportation and service charges, unless these charges have been prepaid. Dynaco reserves the right to limit the service facility or the established service fees to two years from the date of purchase. Dynaco assumes no liability or responsibility for damages or injuries sustained in assembly or operation of this equipment. PARTS LIST PART 3 1 Chassis bottom plate 711421 1 Chassis front panel 711321 1 Chassis back panel 711521 1 Chassis cover 711021 1 “Transformer, power, 10490E 464019 2 Circuit board assembly, amplifier, PC-18 557018 2 Circuit board assembly, preamplifier, PC-17 655017 2 Heat Sink, amplifier 765080 2 AC outlet, Hack 251001 3. Bracket, 2" diameter 717003 | Bracket, 134" diameter 717001 2 Bracket, "UU" shape 717012 d Capacitor, electrolytic, 5000 mid @ &0 volts 284508 l Capacitor, electrolytic 3 section 294228 1 (Control, balance, 220 K dual 167324 l Control, bass, 50 K dual 167514 1 Control, treble, 40 K dual 167404 1 Control, volume, 250 K dual 177254 1 Front plate, gold 769221 1 Fuse holder, with hardware 341001 1 Jack, phone 3 Knob, small Sais 2 Knob, large 7841.26 1 Line cord 322092 4 Set screw for knob, Allen, 5-40 x Ka” 513834 1 Sleeving, insulating 893001 2 Socket strip, 5 inputs 355007 1 Switch, rotary, selector 334604 1 Switch, rocker, lighted, power 334001 2 Switch, rocker, DPDT (6 lugs) 34008 2 Switch, rocker, DPTT (8 lugs) 337001 1 Switch, rocker, QPTT (16 lugs) 366001 2 Terminal strip, 4 screw 374008 1 Terminal strip, 4 lug 374006 2 Wire, #16 heavy gauge 310413 1 Wire, hookup, black 1 Wire, hookup, green 1 Wire, hookup, red 1 Wrench, Allen sot screw, 5-40 058577 1 Card, warranty 1 Manual instruction Envelope #1 997113 RESISTORS 7 10,000 ohm (brown-black-orange) 113103 2 18,000 ohm (brown-gray-orange) 1131483 1 8200 ohm (gray-rod-red) 113822 1 4700 ohm (yellow«violet-red) 113472 2 120 ohm (brown-red-brown) 113121 2 0.47 ohm (yellow. violet-silver) 2 watt 128004 1 10 ohm 10 watt 120100 Parts of similar type which do not change performance will sometimes be included as a matter of expediency. This will account for slight variations in value and appearance. FART # 2 001 mid disc AEREAS 2 0.02 mid disc Shits 2 27 pf disc 244271 2 0.01 mid mylar dipped 268103 2 0022 mfd mylar dipped 285223 2 3300. pf (‚0033 mfd) tubular 265332 2 0 mid tubular electrolytic 283508 Envelope #2 597101 4 Foot, mbber 859001 1 Fuse, 2 ampers, Slo-Blo 142020 52 Lockwasher, #6 617305 l Lockwasher, 34” 617045 4 Lug, ground 639308 8 Lug, spade £20308 25 Nut, hexagonal, #4-40 614245 26 Nut, hexagonal, #6-32 614355 9 Nut hexagonal, 34” 614065 do Screw, machine, #4-40 x 14" 611245 6 Screw, machine, 24-40 x 34" 611205 26 Screw, machine, #6-32 x 14" 611385 В Screw, self-tapping, #6-32 x 34" 613355 14 Screw, sheet metal, #6 brass 612339 4 Spacer, tubular, %4”, aluminum 650261 2 Spacer, tubular, 14”, brass 650021 1 Strain relief, plastic 895001 4 Thumb screw, black 623367 4 Thumb screw, gold 621361 | Washer, flat, 34" 616165 Envelope #3 357019 | (0401 mfd disc, 500 volt 0103 1 Circuit board, PC-19 554019 4 Resistor, 400 ohm, 7 watt, 59% 120401 1 Resistor, 68 chm (blue-gray-black) 103680 4 Diode, rectifier, 3 amp, 200 pry пад 2 Bracket, right-angle 717011 Envelope #4 947318 à “l'ransisior, ZNZ7T2, 571844 red dot 338-2 2 Transistor, ZN3772, 571844 338-1 4 Lockwasher, #6 617305 4 Lug, ground 639308 3 Nut, hexagonal, 26-32 614355 A Screw, machine, #6-32 x 16" 611365 8 Ehoulder washer/spacer, nylon #94001 Envelope #5 967118 4 Insulator, transistor, plastic eosoDní L Thermal compound, capsule 945004 Do not remove the outer insulation from any of the three largest capacitors. 31 ALTERNATE AC LINE VOLTAGE CONNECTIONS The power transformer supplied in the SCA-800 has dual tapped primary windings which are connected im parallel for 100 or 120 volts, and in series for 220 or 240 volts. Assembled SCA-80Q/A amplifiers are connected for 120 volts unless this manual is stamped to indicate another voltage. The 2 ampere slo-blo fuse supplied for standard 120 volt wiring or for the 100 volt option should be replaced with a 1 ampere slo-blo fuse when the amplifier 15 wired for 220 or 240 volt AC lines. The SCA-BOG is designed for use with either 50 Hz or 60 Hz current. Steps 23 through 27 on page 25 of this manual describe the 120 volt connections, Optional connections are dia- grammed and described below. In all cases the red and black wires from the power switch are connected to the red and black AC outlets as described in the instructions. The AC line cord is connected to the red AC outlet terminals. A wire connects AC outlet lug #4 to the tip of the fuse holder. The black transformer lead is connected to the top (side) lug of the fuse holder. No connection is normally made to lug #2 of the 4-lug terminal strip, It is provided in the event that a grounded 3-wire power cord IS to be used. 100 VOLT 100 volt AC line Twist the black-white lead with the black lead and connect them both to the top (side) lug of the fuse holdér, Connect the green wire from the power switch to the top (side) lug of the fuse holder. Twist the green and the vellow transformer leads together and connect them both to AC outlet lus 353. Twist the violet and the violet-white leads together and connect the violet lead to lug #3, and the violet-white lead to lug #1 of the 4-lug terminal strip. За 220 VOLT 220 volt AC line Twist the violet-white and the black-white leads to- pether and connect them both to lug #4 of the 4-lug terminal strip. Connect the green wire from the power switch to lug #4 of the d-lug terminal strip. Twist the violet and the yellow leads together and connect the violet lead to lug #3, and the yellow lead to lug #1 of the 4lug terminal strip, Connect the green transformer lead to AC outlet lug #3. 240 VOLT 240 volt AC line Twist the violet-white and the black-white leads together and connect them both to lug #4 of the 4-lug terminal strip. Connect the green wire from the power switch to lug #4 of the 4-lug terminal strip. Twist the green and vellow transformer leads together and connect the green lead to lug #3, and the yellow lead to lug #1 of the d-lug terminal strip. Connect the violet lead to AC outlet lug #3. Printed in U.S.A.

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