SERVICE MANUAL REPLACEMENT PARTS SG520

SG520 — FRONT VIEW
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Section 1
FUNCTIONS OF CONTROLS AND CONNECTIONS
1.1 PRIMARY FRONT PANEL CONTROLS
1.1.1 POWER.—The POWER pushbutton is an alternate switch: push it once to turn on the system —
push it again to turn the system off. When power is applied, the buttons which happen to be
depressed in the MODE or SOURCE bank are illuminated. The main on-off switch controls not
only the Graphic Controller but also the back panel switched AC outlets.
1.1.2 TONE CONTROLS. — The four vertical straight-line controls at the left of the front panel
permit the operator to emphasize or diminish bass and treble frequencies independently. Most of
the time these are used as ganged controls. By grasping both bass controls at once, for exam-
ple, they can be moved up and down at the same time so that exactly the same tone control set-
ting is supplied to both channels. On the other hand, to give more-bass boost to one loudspeak-
er than the other, only the desired control is used.
When the markers are centered at the ‘O’ position, the response curve of the SG520 is flat.
1.1.3 SOURCE PUSHBUTTONS.—The top row of eight pushbuttons selects the program source which
will be used. Some of these are designed for high-level inputs: devices which provide at least LA -
volt of signal. Others supply additional amplification for low-level devices such as microphones
or phonograph pickups. Individual input sources are described in paragraph 1.4.
1.1.4 MODE PUSHBUTTONS.—The six pushbuttons in the lower row control the manner in which the
stereo channels are fed to the loudspeakers. The TEST button is used in conjunction with the F-22
Remote Relay assembly to permit rapid balance of the entire electrical components. A detailed de-
scription of the F-22 operation and TEST switch will be found in Sect. 3.5.
1.1.5 BALANCE CONTROL.—Sliding the BALANCE control toward the left shifts the emphasis to the
left-hand speaker; moving it toward the right shifts the emphasis to the right-hand speaker. When
the BALANCE control is at the ‘0’ position (and all of the secondary controls have been properly
adjusted) the two channels (A and B) will have identical gain.
1.1.6 VOLUME CONTROL.—The VOLUME control is also a straight-line attenuator. It controls the level
of both channels simultaneously.
1.1.7 LOUDNESS CONTROL.—This switch controls the way in which the volume control operates. With
loudness switched off, the VOLUME control adjusts only sound intensity. With the loudness
switched ON there is emphasis placed on the very low and very high frequencies as the vol-
ume is decreased. This compensates for the tendency of the human ear to lose these frequen-
cies at low listening levels. When it is desired to accomplish all compensation with the individual
bass and treble controls, then the LOUDNESS control can be switched off.
1.2 CONCEALED SECONDARY FRONT PANEL SWITCHES AND JACKS
The lower portion of the face panel of the Graphic Controller is covered by a bottom-hinged
panel which conceals infrequently-used controls, and input and output connectors. This puts
them in a readily accessible location but put of sight when not in use.
1.2.1 FUSE. — At the far left is a Slo-Blo fuse. A 3/10 AMP. fuse is required for 110-120 volt
operation, 15/100 AMP. for 220-240 volt operation. This acts as protection for the Graphic
Controller's internal circuitry. The AC outlets located on the back of the Graphic Controller are
not fused.
1.2.2 MICROPHONE JACK.—Directly to the right of the fuse is a microphone jack for Channel A. The
signal from the microphone jack is fed to the amplifier when the MIC pushbutton is pressed.
1.2.3 RUMBLE FILTER.—The purpose of rumble filter is to diminish low-frequency noise which may
be generated by some record changers, or some of the noises coming from older records. This
slide switch is normally kept in the down or OFF position.
1.2.4 AUXILIARY FRONT INPUTS.—These are high-level input jacks, one for Channel A and one for
Channel B. They are controlled by the SOURCE button marked AUX FRNT. These jacks allow
connection of temporary inputs without having to disrupt the permanent connections made on
the back panel.
1.2.5 SCRATCH FILTER.—This serves to get rid of objectionable high-frequency noises in poor or old
records, a noisy tape recording, or excessive noise in a FM stereo broadcast.
1.2.6 TEST TONE SWITCH.—This switch will usually be in the up or ON position when you use the
TEST button in the MODE bank. A more detailed description of the use of this feature is given
in paragraphs 3.3 and 3.5. | |
1.2.7 TAPE MONITOR.—This switch allows connection of a 3-head tape recorder for recording directly
from any program set up on the Graphic Controller, and at the same time allows listening to
the actual recording as picked up by the playback head. Most high-quality tape recorders have
separate recording and playback preamplifiers and will enable use of this feature. When the
hinged panel is closed, the. TAPE MONITOR switch automatically goes back to its OFF position.
1.2.8 OUT TO RECORDER.—A pair of jacks marked CHANNEL A and CHANNEL B allow making record-
ings directly from the Graphic Controller. The signal which appears at the OUT TO RECORDER
jacks is not affected by the VOLUME or TONE controls. A second set of jacks are located on
the rear panel. Generally, the front panel connections will be used only for temporary connec-
tions for portable machines. |
1.2.9 HEADPHONES JACK.—The next item, to the extreme right, is the HEADPHONES jack used for
monitoring. When headphones are plugged in, signals to the power amplifier are disconnected
and speakers are muted. The signal level at the headphone jack is sufficient to give satisfactory
results with most 8-16 ohm phones (although better performance will be realized with 500-600
ohm or high impedence units).
1.3 FRONT PANEL SCREWDRIVER ADJUSTMENTS
1.3.1 PH LEVEL.—A separate control is provided to adjust the loudness of each phonograph input.
This allows trimming these sources so that when switching from one input to another there
will not be a sudden change in the loudness level.
1.3.2 PH 1 STEREO BALANCE.—A balance control is also provided for the phono-1 input. This makes
it possible to compensate for any minor unbalance in the signals supplied from the two chan-
nels of the phono-1 pickup cartridge. Once this auxiliary balance is set, it matches the SG520
to a particular pickup, and it need not be re-adjusted unless the pickup cartridge is changed.
pe mac tear rarer” Fu
1.3.3 OUTPUT LEVEL TO AMPLIFIER.—Separate output level controls allow adjustment of the strength
of the signal which is fed to a JBL Solid State Energizer or other stereo power amplifier. These
controls are set to accomplish two functions: first, to adjust the gain of each channel individ-
ually so that with the main BALANCE control in its ‘O’ position, the listener hears properly bal-
anced stereo on particular speakers. Secondly, the output level controls limit the loudness at
which you can run the system. To prevent accidental overdriving of the power amplifier or
loudspeakers, and to give the proper range of operation for the volume control, the output level
controls should be set so that normal program material is reproduced just a little louder than
one would ever want to hear it when the VOLUME control is set at ‘8’.
1.4 BACK PANEL CONNECTIONS
All jacks on the back panel receive standard phono pin-plug connectors. TO PREVENT POS-
SIBLE DAMAGE TO THE POWER AMPLIFIER (OR ENERGIZER) OR SPEAKERS, PLUG OR
UNPLUG CABLES ONLY WHEN SYSTEM IS TURNED OFF.
All connections in top row are Channel A. (Left-hand source of sound when fating loud-speak-
ers.) All connections in bottom row are Channel B. (Right-hand source of sound when facing
loud-speakers.) For connecting monophonic sources, use either one plug in Channel A (which
requires the use of the A+B button) or use a “Y” connector.
1.4.1 CHASSIS GROUND.—At the extreme left of the panel is a spring-loaded terminal provided for
connecting to any equipment which requires a separate ground wire. It also can be used for
connecting the entire system to a cold water pipe as a ground.
1.4.2 PHONO 1.—Input from any low-level pickup which requires standard RIAA equalization (any
high-quality cartridge having a minimum of one millivolt rated output).
1.4.3 PHONO 2.—input from a second low-level pickup cartridge or from a tape head. The tape head
connection is required for a tape playback deck which has no electronics built in.
To change the equalization from Magnetic Phono pickup to Tape Head, remove the chassis
bottom plate and adjust the equalization switch to the desired. position. The switch is located
on a bracket immediately behind the front panel output level controls. The positions of the slide
switch are marked MAG PHONO and TAPE HEAD. Refer to Fig. 4-2.
1.4.4 MICROPHONE.—Inputs from any high-impedence microphone or pair of microphones can be con-
nected to these inputs. Generally speaking, no more than 25 of shielded cable should be used.
If making a long run of wire to a microphone in a remote location, this should be a low-im-
pedance microphone and connected through a matching transformer to the Graphic Controller.
Separate microphone jacks for Channel A and Channel B are found on the back panel. The
Channel A microphone input also appears on the front of the Graphic Controller.
1.4.5 TAPE PLAY.—Inputs to these jacks may be from any tape machine which has its own electronics
built in. These jacks are the only input jacks which are not shorted when unused. ALL OTH-
ER INPUTS REMAIN SHORTED UNLESS THE APPROPRIATE SOURCE BUTTON 1S DEPRESSED.
1.4.6 AUX REAR.—This is an all-purpose input which can be connected to any program source which
puts out 0.3 volts of signal or more.
1.4.7 TUN 1.—The most often used tuner should be connected to this input.
1.4.8 TUN 2.—Used for connection of a second tuner.
1.4.9 OUT TO RECORDER.—Outputs from these jacks connect to the ‘“‘line’” or high-level inputs on a
tape recorder. The jacks are duplicated on the front panel for connection to a portable machine.
Note that the Graphic Controller TONE BALANCE and VOLUME controls have no ‘effect on the
signals which appear at these jacks.
1.4.10 OUTPUT TO POWER AMPLIFIER.—Outputs from these jacks connect to the stereo power ampli-
fier or JBL Energizer. The SG520 can drive an impedance as low as 10,000 ohms. The Graphic’
Controller can drive more than one amplifier or JBL Energizer. Two sets of jacks are provided
for such-a purpose.
1.4.11 REMOTE RELAY ACCESSORY FUSE.—This fuse has no affect on the normal operation of the
SG520. It protects against ancaccidental short circuit which could result from improper use of
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the REMOTE RELAY switch. If the fuse should blow, the operation of any remote cuntrol devices
will be affected and hum may possibly be introduced into Channel A.
1.4.12 REMOTE RELAY SWITCH AND SWITCH LOCK.—Unless the JBL F22 remote relay accessory is
connected to the Graphic Controller, this switch should remain in the OFF position. Should it
accidentally be turned ON, the fuse described in the preceding paragraph will blow.
1.4.13 AC OUTLETS (SWITCHED).—The five AC outlets at the extreme right are for plugging in any de-
vice which must be turned on or off along with the Graphic Controller. These would include such
components as tuners, tape recorders, power amplifiers, etc. If the system uses the JBL Solid
State Energizer and does not have the F22 Remote Relay control, an extension cord can be run
from one of these switched outlets to the energizer so that-it will be switched off when the
system is not in use.
1.4.14 UNSWITCHED AC OUTLET.—The single outlet to the left of the power cord is live at all times.
1.4.15 110-120/220-240 VOLT ADJUSTMENT (EXPORT MODEL ONLY).—On the export model Graphic
Controller, there are two holes in the upper portion of the name plate on the rear panel. The
hole on the left is marked 220 VOLTS and the other 110 VOLTS. The Graphic Controller is
shipped with a slotted nylon screw in the 220 VOLT position. If the unit is to be operated from
a 110-120 volt line, change the screw to the opposite hole.
Note that the fuse on the concealed front panel should also be changed whenever the AC line
voltage is changed. For 110-120 volt operation a 0.3 amp Slo-Blo Fuse is required. For 220-240
volt operation the fuse should be changed to a 15/100 amp Slo-Blo unit.
Section 2
PERFORMANCE SPECIFICATIONS AND TESTING
2.1 SPECIFICATIONS
2.1.1 RATED OUTPUT.—3 volts.
2.1.2 HARMONIC DISTORTION AT RATED OUTPUT.—Less than 0.15%, from 20 to 20,000 CPS.
2.1.3 NOISE.—Less than any other preamplifier — only 1 microvoit referred to low-level phono input.
From high-level inputs, 90 db below rated output.
2.1.4 GAIN.—Low-level inputs, 54 db; high-level inputs, 21 db.
2.1.5 FREQUENCY RESPONSE.—Typical response within +14 db, 20-20,000 CPS (with all filters out
of the circuit). |
2.1.6 POWER CONSUMPTION.—20 watts.
2.1.7 TONE CONTROLS — MIN.——18 db at 20 CPS; +16 db at 20,000 CPS. See curves in figure
3-4.
2.1.8 TRANSISTORS AND DIODES.—The unit contains two signal diodes, eight rectifier diodes, a zener
diode, one power transistor and 22 low-level transistors.
2.2 MEASUREMENT TECHNIQUES
Most of the commonly available instruments used in testing audio amplifiers have higher dis-
tortion and/or noise than the SG520 generation by itself relative to the signal. In order of pref-
erence we recommend for the audio oscillator a Radford Low Distortion Oscillator or a Hewlett-
Packard Model H20-200CD. For making IM Distortion measurements we recommend the THD
measurements should be made with a Hewlett-Packard Model 333 or the Audio Instrument Com-
pany Model 168 Analyzer. Because the residual distortion, hum and noise of the SG520 is so
low, the measuring techniques recommended below should be used to be sure that you are
measuring the amplifier and not the test instruments.
2.2.1 TESTING HIGH LEVEL INPUTS
2.2.1.1 Total Harmonic Distortion
Step 1. Connect the oscillator to either the A or B TUNER 1 input jack with a standard shield-
ed cable.
Step 2. Connect the harmonic distortion analyzer and 10,000-ohm, 14-watt carbon load resist-
or to the OUTPUT TO POWER AMPLIFIER jack of the SG520.
Step 3. Both the oscillator and the distortion analyzer should be ‘floated’ or isolated from
the power line grounding the system. This can be done by using a two-blade power plug adaptor
which disconnects the instrument's power cable ground pin. If the Hewlett-Packard oscillator is
used, the output trapsformer is floated from the instrument chassis ground. Do not connect a
common ground between the oscillator and analyzer.
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Figure 2-1 HARMONIC DISTORTION
2.2.1.2 intermodulation Distortion.—In this procedure, the connection of the Audio Instrument Com-
pany Model 168 Analyzer is described because this unit is easier to use. However, the HP equip-
ment can be used in an equivalent setup. |
Step 1. Connect the OSCILLATOR OUT terminals of the intermodulation analyzer to the TUNER
1 jack with a standard shielded cable.
Step 2. Connect a 10,000-0hm carbon load resistor to the OUTPUT TO POWER AMPLIFIER
jack of the SG520.
Step 3. Connect the hot ANALYZER INPUT terminal to the center output terminal of the
SG520. Make no connection between the analyzer ground terminal and the common output ter-
minal of the SG520. This precaution avoids the ground loop that would be completed through
the analyzer common input-output connection.
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FIGURE 2-2 INTERMOCULATION DISTORTION
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2.2.1.3
1,000 ohm 0
Ya -watt
Switchcraft 3502
phono plug
Hum and Noise
Step 1. Connect the HP distortion analyzer or an equivalent (HP 400H) AC voltmeter to the
OUTPUT TO POWER AMPLIFIER jack on the SG520.
Step 2. Terminate the desired high level input (AUX or TUNER) with a phono plug containing
a 1000-ohm resistor. The resistor should have sh ort leads to the phone plug and should be shield-
ed by the plug body. A Switchcraft 3502 phono plug provides a convenient means to contain and
shield a 1,000 ohm 14-watt resistor.
Step 3. Select the correct input with the SG520 SOURCE switch, slide the VOLUME control to
maximum and measure the noise output on the AC voltmeter. Express the noise reading in dec-
ibels below full output (3 volts across 10,000 ohms).
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FIGURE 2-3 HUM AND NOISE
2.2.2 TESTING LOW LEVEL INPUTS
2.2.2.1
2.2.2.2
2.2.2.3
Distortion
Step 1. Use a floating oscillator and analyzer as described in the high-level distortion measur-
ing procedures.
Step 2. If it is desired to make measurements with both channels drive simultaneously, the os-
cillator must be connected to the PHONO input jacks by equal length shielded cables twisted to-
gether for their full length from the oscillator to the input jacks. If this is not done, stray 60-cy-
cle magnetic fields induce in the cable shields. The input hum signal thus generated can easily
be greater than the amplifier distortion products.
Intermodulation Distortion.—The SMPTE* measurement technique specifies that a 4-1 ratio ex-
ists between low and high frequency test signals and is used for test of amplifiers which have uni-
form frequency response. The RIAA equalization used to compensate for magnetic phono cartridge
and recording characteristics prevents accurate interpretation made under SMPTE test conditions.
*Society of Motion Picture and Television Engineers
Hum and Noise
Step 1. Terminate the PHONO 1 (or 2) input jack with a 1000-ohm resistor as noted previously.
Step 2. Set the SOURCE switch at PHONO 1 (or 2).
Step 3. Slide the VOLUME CONTROL all the way up and measure the noise output with the AC
voltmeter. The reading may be expressed as decibels below full output or as “microvolts referred
to the input.” To obtain the latter figure, the output noise reading must be divided by the gain
of the SG520 at 1000 CPS. The nominal low-level gain of the amplifier at this frequency is 510.
The exact gain can be obtained by feeding a one millivolt signal at 1000 CPS into the PHONO in-
put and then measuring the output with an AC voltmeter.
Section 3
CIRCUIT DESCRIPTION
3.1 OVERALL CIRCUIT.
The SG520 Graphic Controller is a transistor stereo preamplifier designed for maximum operator
convenience and versatility. The circuits are somewhat complex because of the linear-actuated
potentiometers, illuminated pushbutton switches, and front panel screwdriver potentiometers
which provide this versatility. The stereo amplifiers are also unique, use large amounts of negative
. feedback in each transistor stage for consistent gain performance. A special circuit is the 1000-
CPS test oscillator which is used for aural balancing. The power supply section provides —24
volts for the amplifiers and oscillator and +24 volts for the F22 accessory. Each of the circuits
is described in. greater detail. For ease in referencing, all components have been numbered
by series: 100 series — Channel A Amplifier
200 series — Channel B Amplifier
300 series — front Panel
400 series — 1000-Cycle Oscillator
500 series — Power Supply
Figure 3-1 is a block diagram of the complete unit. See page 2s.
3.2 PREAMPLIFIER DETAILS.
Each preamplifier is contained on an individual etched-circuit board. The left channel is desig-
nated A; the right channel is designated B. Since both circuits are the same, only channel A
will be described here. The description also applies to channel B when the component numbers
are increased by 100 (for example, R105 becomes R205, in channel B). |
3.2.1 Phono Preamplifier.—The phono preamplifier consists of three PNP transistor stages, О101,
Q102, and Q103. The preamplifier is used only with the low-level inputs for PHONO 1 (J101),
PHONO 2 (J102) or MIC (J103) as selected by the SOURCE pushbutton bank.
In the TAPE PLAY, AUX FRNT, AUX REAR, TUN 1, or TUN switch positions, the preamplifier is
bypassed and Q104 accepts the output of high-level sources. In the low-level (PH1, PH2, or MIC)
switch position a signal of 4 millivolts will produce full amplifier output. At maximum VOLUME
setting, the input sensitivity is 4 millivolts; at reduced settings, the preamplifier will not be
overloaded with levels up to 250 millivolts. In both Q101 and Q102, the amount of DC degener-
ation is greater than AC degeneration, because the emitter load resistance is split. For example,
Q102 has a total DC emitter load resistance of R115 + R116 = 2.4k. But its AC load is only
240 ohms, through AC bypass capacitor C114.
NOTE
The split-resistance emitter load is used in a number of preamplifier stages. When
troubleshooting stages, an open bypass capacitor produces a common symptom: the
ac gain has dropped to the dc gain value.
The output of the phono preamplifier is taken from the emitter of emitter-follower Q103 (PNP)
and ac coupled through C117, through one of the low-level (PH1, PH2, or MIC) selector switches
SW301, and through the TAPE MONITOR switch SW30 (OFF position) to the next amplifier
stage, Q104. The output at the emitter of Q103 is also applied as negative feedback back to
the emitter of Q101 through the networks for RIAA, NARTB, or flat response. This network has
a fixed dc resistance (which sets the overall preamplifier gain), but has lower reactance at high
frequencies. The resultant low-boost and high-cut response of the phono preamplifier compen-
sates for the typical magnetic pickup response curve (figure 3-2) in either the RIAA or NARTB
recording equalization method. The flat response network is used only for the microphone input.
Actually, the “flat” network has a small amount of high-frequency de-emphasis (C112) which
insures amplifier stability and suppresses high-frequency response beyond the audio spectrum.
3.2.2 Emitter Follower Stage Q104.—Transistor Q104 (PNP) receives its input signal from either of
two sources through SW301: (1) direct from the TAPE PLAY, TUNER, or AUX jacks, or (2) out-
put of the phono preamplifier, Q103. In either case, the nominal input level is 250 millivolts.
The Q104 emitter output has a dc load is (R130), the ac load is BALANCE potentiometer, R304.
The emitter follower effectively isolates the BALANCE potentiometer from the input.
3.2.3 Balance, Loudness and Volume Controis.—The channel A BALANCE control R304A is a linear slid-
ing attenuator control which is ganged with the channel B BALANCE control R304B. When the
BALANCE setting is changed, the percentage resistance increases on one potentiometer and
decreases on the other. The wiper of R304A is connected to the VOLUME potentiometer R305.
Both the BALANCE and VOLUME potentiometers are dual-section. The two volume control sec-
tions are matched at the factory to within 2 db tracking.
Loudness compensation is achieved by tapping the VOLUME CONTROL and shunting higher
frequencies to ground, as shown in the simplified schematic, figure 3-4.
When the LOUDNESS switch is ON, capacitor C122 is placed in series with resistor R134.
This causes the higher frequencies to be bypassed to ground. As shown in the diagram, most
of the low frequencies are allowed to flow through the bottom terminal of the VOLUME control to
ground. So, the wiper of the VOLUME control picks off more lows when it is set below the tap
point. The curves in figure 3-3 show how the response varies for different VOLUME control
settings. Beyond the 50 percent setting, the response is flat. Notice that the amount of high fre-
quency de-emphasis levels off at the very high frequencies. This is the shelf level and is deter-
mined by resistor R134 which prevents the high frequencies from being completely shorted to
ground.
3.2. 4 Interstage Amplifier.——Transmitter Q105, (PNP) Q106 (NPN), and Q107 (PNP) are direct-coupled
amplifiers which raise the audio level to provide the high level voltage gain. Negative feedback
through C126 and R141 limits the ac gain of Q105, Q106, and Q107 to approximately 3. The
R141 _
' R139 3. The
minimum ac gain is 3 because this is the ratio of the feedback voltage divider
collector output of Q107 is coupled through C127 to the tone control section.
RESPONSE IN DB.
FREQUENCY IN CYCLES PER SECOND
FIGURE 3-1 TAPE HEAD EQUALIZATION <<
3.2.5 Bass and Treble Controls.—The BASS and TREBLE controls vary the frequency at which boost
or cut begins. For lowest possible distortion, tone control equalization is achieved by feedback
rather than passive networks. Figure 3-4 shows the equivalent circuit of the tone control net-
work and amplifier. When the tone controls are set in a flat position, the overall circuit gain
is one.
SO
Transistors Q108, Q109, and Q110 comprise the tone control amplifier. The output (emitter
of Q110) is fed back to the input (base of Q108) through the tone control network and is summed
with the audio from stage Q107. As shown in figure 3-5, the BASS control varies the frequency
at which the low boost or cut begins. The slope of the equalization curve is relatively constant.
The TREBLE control varies the amount of high boost or cut rather than frequency. The output
of Q110 is applied through a scratch filter to the external power amplifier and has a nominal
level of 3 volts rms for maximum output.
3.2.6 Scratch Filter.—When the front SCRATCH FILTER switch SWO06 is on, capacitor C136 and L101
form a low-pass filter directly at the output. This network attenuates only the higher frequencies,
at about 8 kc. When SWO06 is OFF, the series inductor (L101) has virtually no effect on the
output.
FREQUENCY IN CYCLES PER SECOND
FIGURE 3-2 MAGNETIC PHONO EQUALIZATION
5
‘FREQUENCY IN CYCLES PER SECOND
FIGURE 3-3 RUMBLE AND SCRATCH FILTER RESPONSE
IN DB
RESPONSE
RESPONSE IN DB
20
2 3 4 5 6 7 8 9 2 3 4
; 1000
FREQUENCY IN CYCLES PER SECOND
1
100 3
FIGURE 3-4 LOUDNESS COMPENSATION
CHART NO. S-501-D (soi)
FREQUENCY IN CYCLES PER SECOND
FIGURE 3-5 TONE CONTROL
3.3 OSCILLATOR DETAILS
10
The 1000-cycle test oscillator is contained on an individual circuit board which is powered from
the regulated —21-volt supply. The circuit consists of transistor Q401 (PNP) connected as a
common-collector oscillator. In this oscillator the feedback is between the base and emitter. The
collector does not carry a signal.
The oscillator frequency is determined by toroid L401 and capacitor. C402 which tune to approx-
imately 1000 cps. Because transistor Q401 has no ac voltage gain, the inductor L401 is driven
by the emitter and tapped (an autotransformer) to provide in-phase feedback to the base which
is a larger voltage than is supplied by emitter. The circuit therefore depends on the transistor’s
current gain to sustain oscillation. The output is taken from the emitter.
Potentiometer R401 a EST TONE LEVEL) is used to set the output sine-wave to a level of 0.25
volts rms. Diodes D401 and D402 are clippers which limit the oscillator drive.
3.4 POWER SUPPLY DETAILS
The power supply has two outputs: +24 volts, which is unregulated, and —21 volts regulated.
Bridge rectifier D502-D505 supplies +24 volts through an RC ripple filter. Bridge rectifier
D506-D509 supplies approximately —24 volts which is dropped to —21 volts by the series
regulator. Power transistor Q501 (PNP) is the pass regulator. The output remains constant
since the normal base emitter drop is nearly constant over a wide current range. The emit-
ter follows the base which in turn follows the base of driver Q502. The base of Q502 is ref-
erenced to —22 volts across zener diode D501. So, if the line voltage (or load current) varies,
the Q501 emitter remains at —21 volts. |
Section 4
| REPAIR AND ADJUSTMENT
4.1 SYSTEM TROUBLESHOOTING | |
Amplifier problems reported by the owner of an elaborate stereo system can often be traced to
factors outside the amplifier. Unlike vacuum tube amplifiers, the SG520 Graphic Controller
is normally not subject to gradual deterioration or intermittent hum and noise problems. In fact,
the solid state circuits have proven so reliable that the entire stereo system should be checked
before bringing the SG520 into the shop. Table 4-1 gives some hints for troubleshooting the
system. These checks require only a few minutes to perform.
4.2 AMPLIFIER DISASSEMBLY AND SERVICE |
After isolating any malfunctions to either of the amplifier circuit boards, disassemble the unit
as explained below. Note that the channel A amplifier is on top (figure 4-1) and: may not have
to be removed.
4.2.1 Top and Bottom Cover Removal
Step 1. Using #2 (or #1) Phillips screwdriver, remove five screws which secure top cover to
cabinet. Lift cover away.
Step 2. Repeat for bottom cover. The unit is now accessible for service to the units shown in
figure 4-1.
TABLE 4-1 TROUBLESHOOTING
Trouble Symptom Remedies
A. Entire graphic 1. Check fuse under hinged panel. Replace with correct rating,
controller inoperative. sio-bio.
Pushbuttons do not 2. Suspect wiring of power switch and power transformer.
glow. 3. Export model: check voltage selection.
B. Pushbuttons glow, 1. Press stereo (S) MODE pushbutton and set TEST TONE switch
but unit has no pro- ON. Is 1000-cycle tone heard? If not, refer to symptom C. If only
gram output on either in one channel, trouble is in line amplifier portion of faulty channel.
channel (no noise is If tone is heard in both channels, refer to symptom D.
heard with maximum
VOLUME on MIC
channel).
C. Pushbuttons glow,
but unit has neither
program audio or test
tone output.
Faulty —21-volt power supply.
Faulty line amplifier in both channels.
Faulty MODE switch or wiring.
Faulty low-level amplifiers plus faulty oscillator (symptom E).
PONE
11
D. Test tone is OK, but
program audio is dead.
E. Test tone not heard.
F. No stereo effect
(MODE switch S
button is depressed).
FIGURE 4-1 TOP VIEW
1. Interchange program audio between each of the low-level (PH1,
PH2, or MIC). -
If all inputs are dead, trouble is in the low-level (Q101-Q103) portion
of the amplifier board (or the TAPE MONITOR switch is on).
2. Program audio is dead. Check for faulty connections to phono-
graph pickup, bad cartridge, or faulty tape read head.
1. Faulty test oscillator. To make sure, set TEST TONE switch ON
and connect headphones (or a small loudspeaker) to either of the
front panel OUT TO RECORDER jacks. Then press the TEST and S
buttons at the same time. If the test oscillator is operating, the tone
should be heard.
1. Slide BALANCE control to either extreme. If one channel is not
operating, refer to B and C above.
2. If both channels are operating, check for any condition which
could cause channel' mixing. such as defective system cabling,
cartridge, multiplex tuner, or tape deck.
- 12
FIGURE 4-2 BOTTOM VIEW
3. If program source is at fault, look for wrong stylus pressure,
improper tape player head alignment or improper multiplex.
F-M tuning.
G. Hum in system. 1. Check interconnecting cables for proper shield bonding to plugs.
- 2. Connect #18 ground wire between the amplifer GROUND post
and the system tape deck or turntable motor frame.
3. Move SG520 away from power amp, which may have stray
magnetic field.
4. Check SW307, F-22 switch and fuse F301.
4. Check —21-volt regulator.
5. Suspect ripple in amplifier power supply due to faulty electrolytic
filter capacitor.
6. If hum still exists in a complex system installation, connect the
system GROUND to a true earth ground (cold water pipe, etc.).
4.2.2 Channel A Service.—The channel A amplifier circuit board is accessible from the top of the cabi-
net. To test channel A, proceed as follows: |
Step 1. Connect an audio signal generator to the A PHONO 1 jack. Set the level to approxi-
mately 10.0 millivolts (@ 1 Кс.
Step 2. Press the PH1 button and apply power.
13
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LAME foire e TE ai NR
TT ese e
ys
Step 3. Using an accurate electronic ac voltmeter (HP Model 400 recommended), trace the
signal level at each stage of the amplifier. Refer to figure 4-9 which shows the component loca-
tions.
Step 4. Refer to the troubleshooting chart, table 4-1, when a signal fault is encountered.
Step 5. When a faulty component is found, refer to paragraph 4.4 for replacement recommen-
dations and to Section 5 for parts list.
4.2.3 Channel B Service.—The channel B amplifier must be removed for service. Turn ac power off.
Proceed as follows:
Step 1. Using a #2 (or #1) Phillips screwdriver, remove six 6-32 screws which secure the chan-
nel B circuit board to its chassis.
Step 2. Lift three power leads (red, grey, black twisted together) out of the way. Then lift the
channel B circuit board up.
Step 3. Tilt the circuit board up to a vertical position and tuck a few strips of paper under
the edge to insulate the edge connections from the chassis.
Step 4. In this position, apply power and test the circuits as explained in paragraph 4.2.2, for
the A channel. Refer to table 4-2 for troubleshooting.
4.3 TEST TONE OSCILLATOR DISASSEMBLY AND SERVICE
When the test tone oscillator is known to be inoperative, service it as follows (it is not neces-
sary to remove the front panel):
Step 1. Lay the chassis on its side panel, with the oscillator board components facing up.
Step 2. Using a #2 (or #1) Phillips screwdriver, remove four 6-32 screws which secure the oscil-
lator circuit board to its subpanel.
Step 3. Lift the circuit board out into the clear.The leads are long enough to allow the board to
be placed on the bench for testing.
Step 4. Refer to the troubleshooting suggestions in table 4-3, and to figure 4-3 for component
locations and test point.
NOTE If the transistor and voltages appear OK, but the circuit does not oscillate, the trou-
ble is probably one of the three capacitors in the circuit. |
FIGURE 4-3 TEST TONE OSCILLATOR
14
Trouble Symptom
A. Pop or thump
during turn on or off.
B. Low output level from
low-level portion (Q101-
Q103).
C. Low output level from
line-amplifier portion
(Q104-Q110).
D. No output.
FIGURE 4-4 POWER SUPPLY
Remedies
1. Adjust A-C switch and output shorting switch contacts. Short on
SW 501 ab. should be maintained while switch SW 501 C in either
direction (see figure 4-8).
1. Voltage gain at 1 kc should be 42-44. If less, suspect open
bypass capacitors.
1. Voltage gain at 1 kc should be 3-12. If less, suspect open
bypass capacitors.
1. Using a 20,000 ohms-per-volt meter, verify that at least 1 volt
dc exists between the collector and emitter of each transistor.
If the voltage is near zero, transistor is shorted and must be
replaced.
2. Check each coupling capacitor by measuring ac signal level at
each side of the capacitor. A greatly reduced signal indicates an
open capacitor.
NOTE When applying a test signal, make sure that level does not exceed 0.25 volt.
15
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6 FRONT PANEL DETAIL
FIGURE 4
17
RONT PANEL CONTROLS
ARY F
7 SECOND
FIGURE 4-
18
8 AC AND OUTPUT SWITCH DETAILS
FIGURE 4
19
Trouble Symptom Remedies
A. Low 1-kc tone 1. Faulty coupling capacitor C404 or bypass capacitor C401. Check
amplitude (at input and replace if necessary.
to Q104).
B. No Oscillation. 1. Faulty transistor, Q401.
2. Open capacitors C402 or C403.
3. No power. Make certain that —21-volt power is supplied through
TEST switch contacts.
4. Open potentiometer R504.
5. As a last resort, suspect toroid L401 and check it on a Q meter
* or inductance bridge. If it has a shorted turn, the inductance and
Q will be low.
4.4 POWER SUPPLY SERVICE
To test the power supply, lay the SG520 chassis on its top. All components of the power supply
are readily accessible and are shown in figure 4-4. With power applied, measure all of the volt-
ages and compare them with the voltages shown in figure 4-4.
4.5 FRONT PANEL DISASSEMBLY
To remove the front panel, lay the SG520 chassis on its side and remove three screws on each
side of the panel (at rear of trim strip). Carefully lower the front panel to a near horizontal posi-
tion. The wires are not long enough to allow the panel to be pulled clear of the chassis so all
panel repairs must be carefully made to prevent wire breakage. Panel components are identified
in figures 4-5, 4-6, 4-7.
4.6 PUSHBUTTON SERVICE
The pushbutton banks can be subject to intermittent contact closure. This condition may be due
to either (1) an accumulation of oxide on the contacts or (2), loss of contact wiping pressure.
To correct condition (1), spray on a contact cleaner such as G-C type 8666 Spra-Kleen. To in-
crease wiping pressure, use a pair of needle-nose pliers to bend the stationary contacts together.
This can be done by twisting each contact half inward. |
4.7 Replacement of Resistors and Capacitors.—Resistors and capacitors on the circuit boards must be
replaced as follows:
Step 1. When a component is suspected, clip one of the leads at midpoint to remove it from
the circuit.
Step 2. Check the component.
Step 3. If faulty, clip the other component lead at midpoint.
Step 4. Loop the new component leads over the old stub leader and solder.
CAUTION
DO NOT APPLY HEAT DIRECTLY TO THE PRINTED CIRCUIT BOARD. THIS MAY
CAUSE CIRCUIT FOIL TO LIFT FROM THE BOARD.
F22 RELAY — CIRCUIT DESCRIPTION AND OPERATION
The DC activating signal for the F22 relay is applied between the chassis ground of the SG520
preamplifier and the shield connection of the channel A output cable. Although the shield of
the channel A cable operates at ground potential for the AC signal, a DC potential of about
+20 volts between the CHA shield and the chassis ground. The polarity of the DC signal deter-
mines the mode of operation of the two relays.
The AC power relay, Ryl, is connected through a full wave bridge, Dz, so that a DC signal of
either polarity will energize the relay. Th 500 MFD capacitor, C1, supplies enough delay so
that any momentary interruption in voltage as the polarity is reversed will not cause the relay
to drop out.
The stereo balance relay is connected through a single diode, D1, so that it is polarity-sensitive.
The relay operates only if there is a positive DC voltage at the channel A ground connection.
20
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When the Graphic Controller is first turned on, a control signal of —20 volts appears at the
shield of the channel A output. This operates the AC power relay to turn on the Energizer or
power amplifier. The A-B relay, Ry2, is not actuated because of the series diode. Tracing the
connections through the A-B relay contact, indicates that both loudspeakers are connected in
the normal manner exactly as if the relay were not in the circuit at all.
When the Graphic Controller “test” pushbutton 1$ depressed, the polarity of the control signal
is reversed so that a +20 volt signal appears at the shield of channel A. The AC power relay re-
mains closed and the A—B relay is now actuated. If you will trace the connections through the
contacts Fig. 3-3, you will find that both of the Energizer black output terminals have been dis-
connected and the speakers are now connected in series between the two red Energizer output
terminals. This effectively causes the speakers to respond only to an A—B or difference signal,
enabling the aural null feature to be used.
When trouble-shooting the operation of the F22, remove the cover and see if the two relays are
operating as described Fig. 3-2. In other words, whenever the Graphic Controller is turned on,
the armature of the power relay should be pulled in, but the A—B relay should not be affected.
When the test button is depressed, .the power relay should remain pulled in and the A—B
should also be actuated. If the two relays seem to be operating properly, then the only possible
source of trouble in the system is in the connections between the A—B relay, the loudspeakers,
the power amplifier or Energizer. On the other hand, if the relays are not actuated in the proper
sequence, can check the operating voltage and polarity with an ordinary voltmeter.
NOTE: That it is vitally important that the shield of the channel cable be continuous, and that it
not be connected to the chassis. |
Section 5
REPLACEMENT PARTS AND SCHEMATICS
5.1 REPLACEMENT PARTS. |
Replacement parts for the SG520 Graphic Controller are listed in the following pages. It is rec-
ommended that only JBL replacement parts be used in this high-quality amplifier.
5.1.1 Resistors.—All resistors are the deposited carbon film type. Any failures should be replaced with
the same type. *Ordinary molded composition carbon resistors must not be used. Replace-
ments are availabie directly from JBL.
5.1.2 Capacitors.—Most of the electrolytic capacitors used in the SG520 are specially made. Replace-
ments should be ordered directly from JBL by part number or reference number. Under no cir-
cumstances should inferior-rated electrolytics be substituted. Lower capacities in any circuit will
impair performance. Lower working voltage ratings will cause premature failure. Capacitors have
been selected for low-noise specifications.
*Technicians who are familiar with professional or military dc amplifiers will remember that car-
bon resistors can be more noisy and have a greater resistance change with temperature.
5.1.3 Transistors.—All transistors are selected for current gain, low noise, and other important charac-
teristics. Experience has shown that the current gain (8) from one transistor to the next in any
production batch varies so much that sometimes one will not work well in the circuit. For this
reason, all transistors carry special part numbers and must be ordered from JBL. Note the
color code dot when ordering.
5.2 INFORMATION SERVICE.
Information on parts and service tips can be obtained from the JBL factory Service Department.
Write a letter explaining any unusual problem to:
JBL
Service Department
3249 Casitas Avenue
Los Angeles, California 90039
If it is necessary to return a faulty subassembly or the complete amplifier, first request ship-
ping permission. Then pack the equipment in an over-size carton, completely surround it in cush-
ioning material, and ship by Railway Express or truck express. Be sure to insure the shipment
and prepay the shipping charges. Mark the carton: Fragile — Delicate Electronic Equipment.
22
F22 COMPONENTS
FIGURE 5
23
-21V
Rilo REC
|
LOW LEVEL AMPLIFIER T Cll6
0.001ME
RII8
RIO3 R109 ‹ 180
100K 15K 2N2614
(7 0103
AMF CIO7
CIO3 + are | ME +
25MF 71 Ql F
PHONO 9—- — ОК Dio cios | PHONO
| OUTPUT
INPUT NS + TOOMF 27K RII3
RIOS | | T4 0.047 MF
> 75K 27K R104!
с104 R112 RIS
| 2K
10MF
| RIO6 160
| К RIOS
RIOT с105 Clos
| ' | 300 L 400MF
MF +
| +
| C 108 T 25MF 10K
cios | 121 Г сиз + 120
| 047MF 30K 022MF R
|
| R122 RI23 | Cll RIZ4 | cur
| 5.1K 1.5K i Un
| ~ 18K ~ 100PF
| PHONO 0015] 7
; RIAA
| | TAPE NARTBi—
| MIC FLAT
LOW LEVEL AMPLIFIER
24
REFERENCE NO.
Q
O © OO
Oo
O
о 009009000900 о о 060090 6 000 ©
101, 102, 104
108, 201, 202,
204, 208
103, 203
106, 109
206, 209
107, 110
207, 210
105, 205
101, 102, 137
201, 202, 237
103, 108, 120
127, 131, 135
203, 208, 220
227, 231, 235
104, 132, 204
232
105, 205
106, 206
107, 118, 133
207, 218, 233
109, 115, 121
209, 215, 221
110, 210
111,211
112, 212
113, 213
114, 125
214, 215
116, 130, 134
216, 230, 234
117, 123
217, 223
119, 219
121, 221
122, 222
124, 224
126, 226
128, 129
228, 229
136, 236
101, 102, 107
122, 125, 158
201, 202, 207
222, 258, 225
103, 127, 129
133, 203, 227
229, 233
105, 205
106, 151, 153
206, 251, 253
AMPLIFIER CIRCUIT BOARD
DESCRIPTION
TRANSISTORS
2N508 (selected)
2N2614
2N2712
2N3215
2N3638
CAPACITORS
REFER TO MAIN CHASSIS
25 mF 25V
10 mF 6V
300 mF 6V
100 mF 15V
4 mF 25V
.047 mF 100V
.015 mF 109
.0015 mF 59%
.0001 mF 500V
022 mF 10%
400 mF 3V
.001 mF 500V
2 mF 25V
75 mF 25V
‚47 mF 100V
Refer to Front Panel
200 mF 15V
100 mF eV
.1 mF 100V
.005 mF 500V
RESISTORS
5100 OHM L2W 5%
100K OHM 14W 5%
75K OHM 15W 5%
51K OHM LW 5%
PART NO.
11171
11390
11394
11451
12095
11397
11402
11395
11396
11400
11408
12009
12012
11409
12010
11398
11404
11401
11403
11407
11932
11931
11405
11412
11461
10072
10842
11047
USER NET
$ 2.00
.75
.98
4.95
1.35
1.20
.81
1.41
1.20
‚81
1.32
$ .54
1.44
1.20
.54
.30
.30
.30
.30
29
AMPLIFIER CIRCUIT BOARD CONT.
REFERENCE NO. DESCRIPTION PART NO. USER NET
CAPACITORS
R 108, 208 160 OHM Y,W 5% 11456 30
R 109, 155
209, 255 15K OHM 14W 5% 11046 .30
В 104, 110, 113
152, 204, 210
213, 252 27K OHM 15W 5% 10255 .30
R 111, 132, 211 |
232 270K.OHM 15W 5% 11469 .30
R 112,212 300 OHM 14W 5% 12013 .30
R 114, 136, 214
236 43K OHM LW 59 11608 .30
В 115, 143, 150 |
215, 243, 250 2200 OHM LW 5% 10943 30
R 116, 138 |
216, 238 240 OHM 1LW 5% 11458 .30
R 117,217 7500 OHM Y,W 5% 11463 30
R 118, 218 180 OHM 1LW 5% 11457 30
R 119, 219 2000 OHM 15W 5% 12014 ‚30
R 120, 137, 154
220, 237, 254 10K OHM 15W 5% 11464 $ .30
R 121, 221 130K OHM 1LW 5% 12011 .30
R 123, 223 1500 OHM 1W 5% 10078 .30
R 124, 224 18K OHM LW 5% 11466 .30
R 126, 226 |
162, 262 REFER TO FRONT PANEL
R 128, 228 220K OHM LW 5% 10163 ‚30
R 130, 161
230, 261 4700 OHM LW 5% 10074 .30
R 131, 160 |
231, 260 1000 OHM 14W 5% 10940 .30
R 134, 234 REFER TO FRONT PANEL
R 135, 235 REFER TO FRONT PANEL
R 139, 239 REFER TO FRONT PANEL — OUTPUT LEVEL —
R 140, 240 330 OHM 14W 5% 10082 .30
В 141, 241 3600 OHM LW 5% 10942 30
R 142, 242 56K OHM Y,W 5% 11930 .30
R 144, 244 560 OHM 1LW 5% 10952 .30
R 145, 147
245, 247 3000 OHM LW 5% 11460 .30
R 146, 149
246, 249 REFER TO FRONT PANEL — TONE CONTROLS —
R 148, 248 24K OHM LW 5% 10989 ‚30
R 156, 159
256, 259 82 OHM LW 5% 11455 .30
В 157, 257 110K OHM 16W 5% 11467 30
L 101, 201 Inductor 100 mH 11413 8.25
FRONT PANEL ASSEMBLY
REFERENCE NO. DESCRIPTION PART NO. USER NET
C 122,222 Capacitor 2 MFD 100V 11375 $ 2.25
R 126, 226
162, 262 Resistor 100 OHM 15W 5% 11507 .30
R 134, 234 Resistor 270 OHM 15W 5% 11508 .30
R 135, 235 Resistor 13K OHM 14,W 5% — 11465 .30
R 139, 239 Pot. 1,000 OHM 10% Output Level 11929 1.80
30
+
REFERENCE NO.
R 146, 149
246, 249
R 301
R 302, 303
R 304
R 305
~ SW 301
SW 302
SW 303
SW 304, 305
. 401
SW 305
SW 502A, 8
SW 501
C 507
J 301
J 103, 203, 105
205, 109, 209.
- 501
PL 501, 502, 503
504
MODEL SG520
REFERENCE NO.
401, 403
402
404
401
402
0 С) © ©
FRONT PANEL ASSEMBLY (Cont.)
DESCRIPTION
Slide Pot, Tone Controls
Pot. 10K OHM 2095 Dual Phono Balance
Pot. 10K OHM 209%
Dual Phono Balance
Slide Pot. Balance Control
Slide Pot. Volume Control
Selector Switch Assy.
Mode Switch Assy.
Switch, Tape Monitor
Switch, DPDT, RUMBLE, SCRATCH
Test Tone, Tape, Phono
Switch, Loudness
Power Knob & DPDT Switch
Switch Snap Action, AC Pwr
Capacitor, .047 MFD 600V
Jack, Headphone
Jack, Mike, Aux Input,
Recorder out
Fuse 3/10 Amp. Slo-Blo
Fuseholder
Switch DPDT
Insert Nylon
Pilot Light #1820
Pilot Light Bracket
Door Assembiy
End Cap Left
End Cap Right
Front Panel
Knob, Bass A
Knob, Bass B
Knob, Treble A
Knob, Treble B
Knob, Balance
Knob, Volume
Knob, Loudness
TEST TONE OSCILLATOR
DESCRIPTION
Capacitor 2 mF 25V
Capacitor .22 mF 100V
Capacitor .1 mF 100V
Resistor 13K OHM 15W 5%
Resistor 6800 OHM 15W 5%
Resistor 1600 OHM 1LW 5%
Resistor 10K OHM 1W 5%
Potentiometer 5K OHM
Inductor 100 mH
Transistor 2N2614
Diode IN2090
PART NO.
12439
11845
11342
12440
12441
11355
11356
11803
11361
11448
11317
11380
11941
11364
11471
11378
11377
11317
11470
11420
11482
11354
12205
12202
12211
11366
11367
11368
11369
11370
11371
12174
PART NO.
11401
11606
11405
11465
11604
11675
11464
11344
11413
11390
11602
USER
USER NET
12.00
. 4.50
4.50
21.00
21.00
33.00
21.00
3.15
.54
5.45
3.90
3.15
‚36
3.60
36
30
.69
$ .54
21
48
3.45
13.50
3.16
3.16
39.00
3.00
3.00
3.00
3.00
3.00
3.00
3.00
31
501
501, 502, 503
504, 505
506
501, 502
503
504
505
506
501
502, 503, 504
505, 506, 507
508, 509
Q 501
Q 502
0007202777000 À
SW 503
C 101, 102, 137
201, 202, 237
C 508, 509
S 501, 502, 503
504, 505, 506
SW 307
F 301
J 101, 102, 104
106, 107, 108
110, 111, 112
201, 202, 204
206, 208, 207
210, 211, 212
SW 503
505, 506
J1,2,3,4
Ryl
Ry2
Dl
D2
F1
POWER SUPPLY
Transformer, Power Dom.
Transformer, Power Exp.
Capacitor 2000-2000-1000 mF
Capacitor 2000 mF
Capacitor 2000-2000 mF
Resistor 20 OHM 1LW 5%
Resistor 270 OHM 1W 5%
Resistor 1000 OHM 1,W 5%
Resistor 2200 OHM 1,W 5%
Resistor 5 OHM 5W Wirebound
Diode Zener
Diode, Bridge Encapsulated
Transistor, 2N176
Transistor, 2N2614
Socket, 2N176
Insulator, Mica 2N176
Insulator, Capacitor Mtg.
Terminal Strip, 10 Term.
Terminal Strip, 2 Term.
Voltage selector
REPLACEMENT PARTS LIST AND PRICES
MAIN CHASSIS
.0068 MFD 500V
.01 MFD 500V
Socket, AC
Switch, F22 Relay
1 amp. Fuse
Fuse holder
Individual Jacks
Input Jack Mounting
Strip Assy.
110/220V Selector
(Export only)
Top Cover
Bottom Cover
Case
Foot, Mounting
Ground Terminal
F22 PARTS LIST
Input Jack
Power Relay
A-B Relay
Silicon Diode
Diode, Bridge
Capacitor 500 mF 25V
4 Amp. Slo-Bio
2 Amp. Slo-Blo
Fuse holder
Binding Post Black
11385
11643
11605
11503
11386
11603
11506
10940
10943
11392
12864
11387
11840
11390
10028
10027
10030
11391
10237
15
REFER TO MAIN CHASSIS
13188
13189
10182
11361
11611
11377
11514
11644
11347
11599
12896
11600
10244
10021
11976
11977
11602
11387
11147
11774
1261?
11377
10244
10.50
6.60
6.60
6.60
24.00
30
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Publication SMSG50
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PREAMPLIFIER CIRCUIT BOARD
28
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— ose — —e
OFF
)
—
)
fl)
)
Pa d
p
—e
9 ¢— Phono Input A
| RIAA LOW LEVEL Phono
AMPLIFI ER Output A
(A-Channel)
NARTB 100 SERIES
Flat
FRONT OUTPUT 3109 100
TO RECORDER уу
CHANNEL A, REAR R126
110
\
О
— — — — e
3209 2226
т )
4
+ FRONT OUTPUT
TO RECORDER
$ CHANNEL B, REAR T3210
+
& + Phono Input B
RIAA
LOW LEVEL Phono
AMPLIFIER Output 8
(B- Channel)
`МАКТВ 200 SERIES
FLAT
STEREO REV CHA cH8 A+B TEST
_ | | | | |
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| | | | | | | POWER AMP
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| | | | LINE AMPLIFIER | m
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| Sw303 | [] | ! | | 100 SERIES
| TAPE | о”
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| | | | | | | | | | POWER SUPPLY
| | | | | | =
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| | | | | | | SW306 —O0— HEADPHONE
| | | | | | | | | OUTPUT
| ! | | | | | | Hi SCRATCH J301
| | | | | | | | | FILTER
I | | | | | | | |
1 | | | | | | | | | | 100
| | | | | | | I | | R262
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| 1
| a | ! | | LINE AMPLIFIER
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|] 200 SERIES
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| ТОМЕ: ASSEMBLY Reg. Г |
| OSCILLATOR _ | LAMPS FOR
— ASSEMBLY 500 SERIES SELECTOR AND
400 SERIES | MODE SWITCH
TONE | amp |! FIGURE 3-1
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BLOCK DIAGRAM
JBL GRAPHIC CONTROLLER
27
—_. = Ge SE Sm cme wens
LINE AMPLIFIER
(A-Chonnel)
100 SERIES
500 SERIES
LINE AMPLIFIER
(B-Channel)
200 SERIES
POWER
SUPPLY
ASSEMBLY
LF RUMBLE
ТОМЕ.
OSCILLATOR
ASSEMBLY
400 SERIES
Test Tone Qurpu!
Phono
Output A
J210
LOW LEVEL
AMPLIFIER
(A-Channel)
100 SERIES
LOW LEVEL
AMPLIFIER
(8- Channel)
200 SERIES
FRONT OUTPUT
CHANNEL A, REAR
CHANNEL B, REAR
TO RECORDER
FRONT OUTPUT
TO RECORDER
Phono Input B
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sw308
TAPE HEAD
FRONT
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1
SW301 AUX
MAG PHONO
TAPE
10K
|
|
|
INPUTS
J101-8
PHONO 1
TAPE PLAY
AUX FRONT
AUX REAR
CHANNEL "A"
PHONO 2
MIC (Rear)
PHONO 1
BALANCE
R301
CHANNEL "8"
PHONO 1
PHONO 2
-21V
REG
1K
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R146
BASS
сиг 30K
Tw
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3K 82
3 oo SW 304 ) QI09
L.F. FILTER 2NZ7°2
Q104 Io
cis | ZNäzıs 101
L
c123 2N3215 | ' * cise 100MH
MF
ci27 * ‚OUTPUT
BMF
VOLUME | |
R305 + TREBLE
or \ |+ ro RISO H.F. FILTER
R133 7 | DK ‘ 82 IK SW 306
100K 100MF |
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RI44
RI35 560
13K
; RI43 CI36
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OUTPUT
LEVEL
LINE AMPLIFIER
LAMP
-21v R502 RS50I + 24v
REGULATED 20 20
| Ese T 501 o MAA
3/10A SLO BLO 1000MF =
_ SWS | V/WH GREEN | C503 [_c502 }`с50! 1
L40I Q 401 nu
100 MH 2N2614 C307 И 0502-5
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C402 0. 22MF dos 0047 ME Г | | | BLUE .
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a . 6 C505
R405 1 —— BLK № - con 050! >< 2000MF 2000MF
em ¢ 40l 10K © SWITCH SHOWN +| 2000MF |+| | ZAZ28A |+ |+
2MF | IN 220-VOLT POSITION d ANA IL MALLORY
R407 + (export model only) 506
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TONE OSCILLATOR POWER SUPPLY ASSEMBLY
25