Marantz 14, 15 Solid State Amplifier Service Manual

Below you will find brief information for Model 14, Model 15 Solid State Amplifiers. This document serves as a comprehensive guide for servicing these Marantz amplifiers, detailing their circuit description, technical specifications, and necessary test equipment. It outlines procedures for critical adjustments like D-C balance and bias, along with extensive troubleshooting tips for common field issues, ensuring optimal performance and reliable operation of the solid-state amplifier.

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SECTION
TABLE OF CONTENTS
Introduction
Circuit Description
Technical Specifications
Test Equipment Required for Servicing
Conversion to 240 Volt Operation
Disassembly Instructions
Performance Verification Test Procedure
Output Trimming Procedure
Trouble Analysis Procedure
FIGURE
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LIST OF ILLUSTRATIONS
TITLE
Trim Box Schematic Diagram
240 Volt Conversion Diagram
Performance Verification Test Set-Up
Location of D-C Balance Adjustment
Oscilloscope X-Y Display Showing Clipping
Residual Output of Analyzer Showing Clipping
Residual Output of Analyzer, Rated Distortion at 2000 Hz
Residual Output of Analyzer, Rated Distortion at 20,000 Hz
Residual Output of Analyzer, Rated Distortion at 20 Hz
Residual Output of Analyzer at Clipping, Without Evidence of
Parasitic Oscillation at 20 Hz
Residual Output of Analyzer at Clipping, With Evidence of
Parasitic Oscillation at 20 Hz
Solid State Amplifier Transistor and Diode Locations
Solid State Amplifier Model 14, Schematic Diagram and Volt-
age Chart
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INTRODUCTION
This service manual was prepared for use by
Authorized Warranty Stations and contains service
data for the Marantz Models 14 and 15 Solid State
Amplifiers.
Adjustment information and troubleshooting hints
included in this manual are intended for use by the
knowledgeable and experienced technician only. All
instructions should be read carefully and understood
fully before proceeding with any service. No attempt
should be made to proceed without a good under-
standing of the Solid State Amplifier operation and
an adequate proficiency in the use of the test equip-
ment required for servicing.
Symptoms (and their remedies) listed in the
Troubleshooting Section are those which might occur
in some units—based upon information derived from
a significant sampling of units in the field. As the
Marantz Company becomes aware of other field prob-
lems, supplementary service bulletins will be issued
to all stations. To improve this service, all problems
(and their solutions) not covered in this service
manual should be brought to the attention of the
Service Manager at our New York location.
NOTE
Performance Verification, Output Trim-
ming, and Trouble Analysis Procedures in
this manual apply to a Model 14 amplifier
or to each of two modules comprising a
Model 15 amplifier.
CIRCUIT DESCRIPTION
The signal to be amplified is fed from the input
jack through C8 and R14 to the base of Q103.
Refer to the schematic diagram of the amplifier, Fig-
ure 13. Resistor R14 and capacitor C9 is an R-F
filter which bypasses to ground any R-F appearing at
the input jack. This eliminates the possibility of
detected R-F from reaching the loudspeaker termi-
nals and causing unwanted signals in the loudspeak-
ers. Q103 is one-half of a differential amplifier
consisting of Q102 and Q103. The constant current
supply for this differential amplifier is Q101. Q101
is biased by a network of resistors, diodes, and a
zener diode in order to establish a slow turn-on
characteristic, and a constant current of about 4
milli-amperes. Slow turn-on allows all other equip-
ment to be stabilized before sound can be heard
from the loudspeakers.
The combination of C1, R1, R2, and R17 comprise
a time constant circuit for turning on Q101. If Q101
is not turned on, Q102 through Q106 will not be
turned on either, because the drive current for these
transistors is derived from Q101. As a result, there
will not be any current drive in the printed circuit
board. Without current drive there will be no current
flowing through Q107 and the bias network. Q108
and Q111 will remain at cut-off, and therefore the
output voltage will be at virtual ground or zero.
During turn-on, the voltage present at the junction
of C1 and CR104 may be negative. To prevent this
from affecting the turn-on time constant, CR104
clamps this point to ground during turn-on. CR104
also provides a discharge path to ground for C1 dur-
ing turn-off. Rapid discharge of Cl ensures proper
functioning of the slow turn-on feature in the event
the amplifier is turned-on immediately after it has
been turned-off. The network consisting of CR101,
CR102, CR103, and R4 insures that Q101 always
delivers a constant current of 4 milli-amperes under
high or low line voltage conditions.
The differential amplifier consisting of Q102 and
Q103 delivers current to a second differential am-
plifier Q105 and Q106. In order to supply a push-
pull drive to drivers Q108 and Q111, current inver-
sion is required. This is accomplished in Q104, a
PNP transistor functioning as a current inverter.
Q105 delivers current to the base of Q104, which
inverts the signal. The collector of Q104 and the
collector of Q106 supply the plus and minus drives,
respectively. This allows the circuit board to deliver
current to drivers Q108 and Q111 in a symmetri-
cal push-pull fashion. Diodes CR106 and CR107
limit the input signal swing into Q105 and Q106 dur-
ing short circuit conditions in the output.
The Solid State Amplifier uses two full-wave power
supplies (separate B+ and B— supplies) and is a
complementary-symmetry configuration. The entire
amplifier, with the exception of the input network, is
direct-coupled.
Resistor R8 (3.3K ohms, 2 watt) shunted by C3
(10UF, 100 volt electrolytic) allows the collector of
Q105 to operate at a lower potential, thus reducing
its dissipation. (This is essentially a current amplifier
rather than a voltage amplifier.)
The D-C balance control R19 sets the output ter-
minals at virtual ground potential (zero D-C). Small
tolerances are compensated for by adjusting the D-C
operating point of the input differential amplifier
Q102 and Q103 so as to establish a zero D-C output
reference voltage at the loudspeaker terminals. lt is
essential that this voltage be kept as low as possible.
D-C feedback from the loudspeaker terminals is ap-
plied through resistor R13 (10K-ohms) and R12
(91K ohms) to the base of Q102. The signal at the
loudspeaker terminals, therefore, is the source from
which the base of Q102 gets its drive. The resistance
of this network corresponds to R15 (100K-ohms)
from the Q103 base to ground. Thus the differential
amplifier sees the same D-C resistance on its bases,
and therefore the transistors operate under the same
D-C conditions. The A-C gain of the amplifier is estab-
lished by the combination of resistors R11 and R13.
R12 is by-passed by capacitor C5 (.47 UF), so that
a-c is not developed across it. Diode CR105 ensures
that the voltage across C7, a polarized capacitor,
never exceeds —0.7 volt.
Q107 in conjunction with CR110 and control R30
constitute a “variable diode’ circuit which enables
the proper bias voltage to be set across Ql07
coliector-to-emitter while still maintaining a logarith-
mic or diode characteristic. This is the bias setting
for the output stages Q110 and Q113.
Drivers Q108 and Q111 deliver current through
series regulators Q109 and Q112 to the base of the
output transistors Q110 and Q113. The base of the
regulators Q109 and Q112 are connected to the plus
and minus power supplies through zener diodes
CR109 and CR111, respectively. This serves to limit
the current through the regulators to the output
stages as follows. As the current in the output stages
rises, the voltage drop across resistors R27 and R35
(.47-0hm, 10 watt) increases. When this voltage drop
plus the voltage drop from base-to-emitter of tran-
sistors Q110 and Q113, plus the voltage drop from
base-to-emitter of regulators Q108 and Q112 equals
the zener voltage, any further increase in current
through the regulators to the output stage is limited.
In other words, as the current from Q108 or Q111
drivers increases, the tendency of the whole regu-
lator system is to rise even further. However, since
the base of the regulators are clamped by the zener
diodes to a fixed potential, any further increase in
current will be by-passed around the regulators
through R24 and R32 (100-ohms, 1 watt) and there-
fore will not appear at the base of the output devices.
Lamps DS101 and DS102 in the collectors of the
output stages serve a dual purpose: (1) they dissi-
pate long term power from the output devices dur-
ing accidental short circuit which may occur at the
loudspeaker terminals or during overload conditions
as the amplifier is driven to its clipping point and
beyond, (2) They act as overload indicators to signal
that the unit is being over driven. They do not dis-
sipate an appreciable amount of instantaneous power.
The stud rectifiers CR112 and CR113 minimize
distortion, especially at the high frequency end of
the band. Coil L5 shunted by resistor R37 (2.2-ohms,
1 watt) reduce the small amounts of very high fre-
quency excursions that would appear at the loud-
speaker terminals.
TECHNICAL SPECIFICATIONS
Input Signal for Rated Power Output. 0 1 volt rms
Input Impedance . 100K ohms
Frequency Response 1.112111 11000. ... Within 1 db, 10 to 60 KHz.
Power Output, 20 Hz to 20,000 Hz (each channel) . 70 watts rms at 4 ohms load
60 watts rms at 8 ohms load
40 watts rms at 16 ohms load
Damping Factor . .. . ... | Greater than 150 with 8-ohm load
Overload Recovery . .. ........ Instantaneous
Total Harmonic Distortion. . . Less than 0.1% with 4 to 16 ohm load—
typically 0.03% with 8-ohm or higher
load—at full rated output, at any fre-
quency from 20 to 20,000 Hz. Distortion
decreases as output level is lowered.
Total Noise (shorted input broadband). ........... Better than 90 dB below
60 watts into 8 ohms
Power Bandwidth# 111111111111 110 8 Hz to 60 KHz at 8 ohms
Continuous output at mid-frequencies&reg; ........... 70 watts at 8 ohms
Dynamic (music) output at mid-frequencies* .. 85 Watts at 8 ohms
Difference in frequency response*. 111111111001 +0.05 dB
Power Requirements*# 111111111111 105 to 135 volts
50 to 60 Hz.
240 watts
Dimensions .......... LL 110 15-3/8 inches wide
5-3/4 inches high
&amp; inches deep
Weight (as shipped) ......... Model 14—18 pounds; Model 15—34 pounds
* From IHF Standard (IHF-A-201 1966)
“* Split primary windings permit adaptation to 210-270 volts
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Specifications subject to change without notice
TEST EQUIPMENT REQUIRED FOR SERVICING
Table | lists the test equipment required for servicing the Model 14 and 15
Solid State Amplifiers. The trim box listed in the table must be fabricated from
the components shown in the schematic diagram, figure 1.
TABLE |. TEST EQUIPMENT REQUIRED
Distortion Analyzer ........... Hewlett Packard 331A or 333A
Audio Oscillator . | Hewlett Packard H20-200CD
&Ouml;scilloSscOpe ........................ Tektronix 503 (or equal wideband)
RCA Senior Volt-Ohmyst .. 11111111 LL LL LL LL 1110 WV-98C
2 Load Resistors ............... Dale NH-250 (8 ohms +0.5%, 250 watts)
Wattmeter ....... .......... aaa Simpson Model 390
Trim BOX... LL LL LL LL LL 1110 See figure 1
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Figure 1. Trim Box Schematic Diagram
CONVERSION TO 240 VOLT OPERATION
To convert the amplifier from 120 Volt opera- 2. Secure the terminal with a 6-32 x 1/4-inch
tion to 240 Volt operation, proceed as follows. Figure machine screw.
2 shows {he connections for both before and after 3. Connect the black/white and black/green
t f dst h | inal.
1. Install a threaded insulated terminal (Marantz ransformer leads together at this terminal
part number 87-1020) in the spare hole 4, Change fuse to 1-1/2A, AGC or 3AG.
located near the line cord.
BLK/YEL — BLK/YEL
21/2 A. AGC | 1/2 A. AGC
OR 3AG OR 3AG
) TERMINAL
87-1020
120V 240V
50-60 Hz 50-60 Hz
&copy;
BLK TPS
Figure 2. 240 Volt Conversion Diagram
DISASSEMBLY INSTRUCTIONS
MODEL 14. To disassemble the Model 14 Solid State
Amplifier for servicing, proceed as follows:
1. Remove the four larger Phillips head screws
from the top grill and remove the grill.
2. Remove the rubber feet securing the grill at
the bottom of the amplifier. Remove the grill.
3. Remove the four Phillips head screws that se-
cure the rear panel to the main chassis. This will
permit access to the printed circuit board.
4. The other components are accessible by remov-
ing four Phillips head screws holding the U-shaped
extrusion on which the rear panel is mounted. Two of
these screws are located at each side of the amplifier.
MODEL 15. To disassemble the Model 15 Solid State
Amplifier for servicing, proceed as follows:
1. Disconnect the power cord inter-connecting the
two modules.
2. Being very careful not to mar the panel finish
or the hex head bolts, remove the four bolts that
secure the panel to the amplifier modules.
3. Gently pull the panel forward and disconnect
the pilot lamps.
4. Loosen and remove the No. 8 cap screws using
a 9/64-inch Allen wrench.
5. Remove the four Phillips head screws from the
center plate that holds the two modules together. The
plate is at the rear of the amplifier.
6. Separate the modules and proceed with dis-
assembly of the Model 14.
PERFORMANCE VERIFICATION TEST PROCEDURE
A. TEST EQUIPMENT. Refer to Table | for the test
equipment required.
B. PRELIMINARY PROCEDURE.
1. Set up the amplifier module to be tested and
the test equipment as shown in figure 3.
2. If a Model 15 is to be tested, disconnect the
interconnecting power cord between modules
and test one module at a time.
3. Make sure that the connections between the
the resistive load and the LOUDSPEAKER ter-
minals of the amplifier module have negli-
gible resistance compared with the resistance
of the load itself. Appreciable resistance in
the wiring adds to the total load, resulting in
inaccurate measurement of output power.
C. IDLING CURRENT AND D-C BALANCE TEST.
1. Connect a shorting plug to the INPUT jack
of the amplifier module.
2. Make sure that the Variac is set for zero volt
before applying line power to the amplifier.
3. Turn up the Variac slowly while observing the
voltmeter and the wattmeter. When the line
voltage reaches approximately 90 volts, the
amplifier should turn on, and the line watt-
meter should indicate between 5 and 15
watts. If the wattmeter indicates either zero
watt or greater than 100 watts, a defect
exists. Turn off the Varaic and refer to the
Trouble Analysis section of this manual.
4. Advance the Variac until the voltmeter indi-
cates 120 volts. If the wattmeter does not
indicate 30 = 1 watt, adjust bias potenti-
ometer R30, as follows:
a. Remove the top grill cover from unit.
b. Using a long, narrow, insulated screw-
driver, adjust bias control R30 until 30
watts is obtained on the wattmeter. The
bias control is located in the lower left
hand corner of each module.
5. Turn off the Variac (using switch only) and
discharge C15 and C21 (the large electro-
lytics), using a 10-ohm, 1l-watt resistor. Do
not use a screwdriver to discharge the
capacitors.
6. Set the controls of the DC VTVM for plus (+)
DC measurement on the 1.5-volt scale. Short
the VTVM test leads together and offset the
pointer to the zero center of the scale.
7. Connect the negative lead of the VTVM to the
ground (gray) LOUDSPEAKER terminal and
the positive lead to the hot (red) terminal on
the amplifier.
8.
10.
Temporarily remove the amplifier line cord
from the Variac and turn on and adjust the
Variac for 120 volts output. Turn off the
Variac, and reconnect the amplifier line cord.
Turn on the Variac, applying the full 120-volt
line to the amplifier, while observing the
VTVM. If the meter pointer swings off-scale
in either the positive or negative direction,
remove power and refer to the Trouble
Analysis Section.
If the meter indicates on-scale, but not at the
zero center established in step no. 6, remove
the access cover screw (See Figure 4) and
adjust potentiometer R19, using a small,
narrow-blade screwdriver, so that a zero cen-
ter scale indication is obtained. This repre-
sents zero volts, de.
D. TOTAL HUM AND NOISE TEST
1.
2.
Connect a shorting plug to the INPUT jack
of amplifier module.
Connect an 8-ohm resistive load and a dis-
tortion analyzer across the LOUDSPEAKER
terminals.
Set the distortion analyzer controls for volt-
age measurement, and apply power to the
amplifier.
If the analyzer indicates greater than 0.0007
volts (—90 dB), refer to the Trouble Analysis
Section. Typical noise values are 0.0002 volt
(—100 dB).
E. OUTPUT CLIPPING TEST
1.
Connect the audio generator to the INPUT
jack of amplifier module. Set frequency to
2000 Hz.
Connect the 4-ohm resistive load and the dis-
tortion analyzer to the LOUDSPEAKER 1ег-
minals.
Set distortion analyzer controls for voltage
measurement on the 30-volt scale.
Turn on the amplifier and increase the out-
put of the audio generator, until clipping oc-
curs, as displayed on the oscilloscope. See
Figure 5.
Vary the output of the audio generator while
observing the oscilloscope display. Verify
that the distortion analyzer indication is be-
tween 17.32 and 18.0 volts at the point where
clipping is barely discernible. If the clipping-
point voltage is below 17.32 volts or above
18.0 volts, refer to the Output Trimming
Procedure Section of this manual.
6. Set the distortion analyzer controls for dis-
tortion measurement on the 109 scale, at
2000 Hz.
Adjust the controls of distortion analyzer, if
required, to obtain an oscilloscope display
similar to that shown in Figure 6.
Observe the sharp clipping spikes at each
end of the pattern. As the audio generator
output is varied slightly, the spikes should
become visible at the same time, and should
have equal amplitudes. If the spikes do not
appear simultaneously, or have noticeably
different amplitudes, refer to the Output
Trimming Procedure.
F. HARMONIC DISTORTION TEST
1.
2.
Connect the audio generator to the INPUT
jack of the amplifier module.
Connect the 4-ohm resistive load and the
distortion analyzer to the LOUDSPEAKER
terminals.
Set the frequency controls of the audio gen-
erator and the distortion analyzer to 2000 Hz.
Set the controls of the analyzer for voltage
measurement on the 30-volt scale.
Adjust the generator output level until the
analyzer meter indicates 16.73 volts. (This
represents 70 watts into a 4-ohm load.)
Measure the total harmonic distortion with
the analyzer and verify that it is less than
0.1%. See Figure 7.
Set the frequency controls of the generator
and the analyzer to 20,000 Hz and repeat
steps 4, 5, and 6. See Figure 6.
Set the frequency controls of the generator
and the analyzer to 20 Hz and repeat steps
4, 5, and 6. See Figure 9.
G. PARASITIC OSCILLATION AND SHORT CIRCUIT
TEST.
1. Set frequency controls of audio generator and
distortion analyzer to 20 Hz.
2. Set distortion analyzer controls for distortion
measurement on the 109; scale.
3. Connect the 4-ohm resistive load and the dis-
tortion analyzer to the LOUDSPEAKER ter-
minals of the amplifier.
4. Adjust the generator output level until clip-
ping occurs, as displayed by the oscilloscope.
See Figure 10.
5. Verify that the display is free of parasitic
oscillations. If parasitics appear, as shown in
Figure 11, refer to the Trouble Analysis
Section.
|
6. Disconnect the 4-ohm resistive load from the
amplifier, but do not disconnect the distor-
tion analyzer.
7. Adjust the generator output level until clip-
ping occurs. See Figure 10.
8. Verify that the display is free of parasitic
oscillations. If parasitics appear, under this
no-load test condition, refer to Trouble An-
alysis section.
CAUTION
Do not perform short circuit test if
amplifier shows any signs of para-
sitic oscillation.
9. Connect a short circuit across the amplifier
LOUDSPEAKER terminals for about 10 sec-
onds. The overload indicator lamps should
light very brightly until the short circuit is
removed.
OUTPUT TRIMMING PROCEDURE
1. Set up test equipment and amplifier as in Har-
monic Distortion test (paragraph F), steps 1 thru 4.
2. If amplifier starts to clip before 17.32 volts (75
watts) decrease the value of R28 or R36 by shunting
with another resistor. The proper value may be de-
termined by connecting the trim box (figure 1) across
R28 or R36 and selecting the value that will permit
the amplifier to clip symmetrically between 17.32
and 18 volts (75 to 80 watts).
3. In some cases it may be necessary to use two
resistors in parallel in order to obtain proper clipping
point voltage.
4. If it is not possible to obtain a high enough
clipping point voltage with the above method, it will
be necessary to try substitution of the output, driver,
or regulator transistors.
5. If clipping occurs at a point above 18 volts (80
watts), the value of resistor R28 or R36 should be
increased.
6. To increase the value of R28 or R36, remove
the black jumper wire connecting one end of the
resistor to the socket contact of output transistor
Q110 or Q113 (DTM-13 or DTM-14) and substitute
a suitable length of resistance wire. Use of 24 gauge,
1/4-ohm per foot wire (approximate requirements)
will result in convenient lengths. |
7. The length of the resistance wire required must
be determined empirically.
8. If the clipping point voltage still remains high,
substitute the output, driver, or regulator transistors.
TROUBLE ANALYSIS PROCEDURE
The trouble analysis procedure that follows con-
tains some of the typical troubie symptoms encoun-
tered in the field and their remedies. Other field
problems will be covered through service bulletins
(supplementary to this manual) which will be issued
to all stations. Other servicing aids included in this
manual are a component location illustration, figure
12, which locates those transistors and diodes com-
monly requiring servicing in the field, and the sche-
matic diagram of the Solid State Amplifier, figure 13.
The schematic diagram contains a Voltage Chart
which lists typical voltages taken at various test
points in a normally-operating amplifier.
NOTE
Performance Verification is necessary fol-
lowing any repair.
SYMPTOM
1. Excessive line consumption (100 watts or more).
PROCEDURE
a. Check for shorted rectifiers CR114, CR116
(DHC 200R), CR115, CR117 (DHC 200), Clb,
C21.
b. Check for shorted transistors Q107 through Q113
(DTM10, 11, 12, 13, 14), or zener diodes CR109
or CR111 (DIN4732A). Also check for open
lamps DS101, DS102, control R30, and bias
diode CR110.
CAUTION
Because the driver and output stages are direct coupled, many components may fail as a direct result of an
initial component failure. If a shorted transistor or Zener diode is found, or an open lamp, control or bias
diode, be sure to check the remaining driver and output components for short or open circuits before re-energiz-
ing the amplifier. After replacement of any of these components, increase the Variac voltage slowly while
monitoring the wattmeter as described in paragraph C of Performance Verification.
2. No line consumption or zero bias.
3. High d-c voltage at loudspeaker terminals before
time delay circuit is deactivated.
4, High d-c voltage at loudspeaker terminals at all
times.
5. No D-C Balance.
6. High hum and noise level.
7. Parasitic Oscillation.
Check for open fuse, transistors Q101 (DTM6), Q107
through Q113 (DTM10, 11, 12, 13, 14), zener diode
CR109 or CR111 (DIN4732A), or overload indicators
DS101 and DS102.
Check transistors Q105 and Q106 (DTM8), and Q104
(DTM9) for leakage. Voltage on these transistors
should not vary more than 1 volt.
Check for shorted transistors Q104 (DTM9), Q105 or
Q106 (DTMS).
Check for open transistors Q104 (DTM9), Q105 or
Q106 (DTM8).
Check by substitution transistors Q101, Q102, and
Q103 (DTM6). Note that Q102 and Q103 are a
matched pair and must be replaced as a pair.
a. Remove capacitors C14 (.22 UF) and C17 (.0047
UF).
b. Check by substitution transistors Q113 (DTM13)
and Q114 (DTM14).
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ALL WAVEFORMS TAKEN WITH OSCILLOSCOPE
SENSITIVITY SET AT 10 MV/CM.
ACCESS COVER SCREW
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OSPEAKER
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= MAX
Figure 4. Location of D-C Balance Adjustment
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Figure 12. Solid State Amplifier Transistor and Diode Locations
TEST
POINT
Q101
Q102
Q103
Q104
Q105
Q106
Q107
Q108
Q109
Q110
Q111
Q112
Q113
B+
B—
BASE
(V)
+30
+0.7
+0.72
+41
—40
—40
—0.56
+1.33
+41
+42
—1.2
—41
—42
+42
—42
EMITTER
(V)
+30
+1.34
+1.34
+42
—41
—41
—1.8
+0.7
+42
+42
—0.66
—42
—42
VOLTAGE CHART
NOTES
COLLECTOR
(V)
+1.34
—40
—40
+13
+1.8
—1.7
+1.3
+41
+41
+0.8
—41
—41
—0.8
NOTES AND CONDITIONS:
1. All DC voltages &pound;109.
2. All voltages measured using a VTVM.
3. All voltages measured while maintaining a
120-volt line input. |
4. All voltages measured with input jack shorted.
5. Transistor voltages measured with respect to
B—.
6. B+ and B— measured with respect to ground
bus.
CIRCUIT NO. MARANTZ NO. CIRCUIT NO. MARANTZ NO.
CRIOI D1IN4736A QIOI DTM6
CRIO2,8 DMR2360 Q!lO2,3 MATCHED DTM6
CRIO3,5,6,7 DBTRI557 QI04 DTM9
CRIO4 DXIN457 @105, 6 DTMS8
CRIO9, II DIN4732A Ql107, DTMIO
СКО DBTRI559 Q108,12 DTMII
CRIIZ2 DMRII2OR QI09, II DTMI2
CRII3 DMIT2O Qll3 DTMI3
CR114,116 DHC200R ео DTMI4
UNLESS OTHERWISE SPECIFIED: CAPACITORS IN DECIMALS ARE uf
ALL OTHER ARE pf
F DENOTES PRECISION FILM RESISTORS
Xx DENOTES COMPONENTS SELECTED FOR OPTIMUM CIRCUIT OPERATION,
ALL RESISTORS ARE IN OHMS, 1/4 W EXCEPT AS NOTED.
A DENOTES COMPONENTS THAT MAY BE OMITTED FROM UNITS.
—]]
|
р-не == ——————— — —
ANN e —Ф
8 1
CRIOI 330 RE R7 R29 CIS
47 47 820 5450uf
RI e 1 RS | SW 50V
56K RI R40 22 LS |
150 * 0104 Y CRIOB —
Cl DSIO3
т: 50 uf CRIO2 + &copy; 6.3V
50V FA
Q 101 p
02 c3 RS шт =
в? CRIO3 ET Sout lOuf $ 3.3K LAMP
IOOK 50V IOOV 2W Lea
| 038 CRII4 TI
RA —14
3.3K |
1/2W |
4 CRIO4 CRII5
crue
o р , .
Lor CRII2 FUSE
100uf CRIT 2.5AMP
cs ви &copy;) 25V { 3AG
ir 470 LCI7
; — 0047
RIZ r13(F) A CRII3
‘ wv
эк IOK
OL и”
3.3M ||
QI02 100
с12
‚00! R37
? ! 2.2 L
TA | IW 5
05102
RI8 RED
cio + 750 SPKRS
‚001 RIO?
6
CRIO | GRAY
RI4 L cn Ll
33K T 033 —
nes RI9
100 500
4 .
QIO3
| C20
750 =
R2
| 2 e La
R22 R39 c2i
RIT 47 3.3K 5450 uf
IBOK SOV
VW +—— 4 +
Figure 13. Solid State Amplifier Model 14,
Schematic Diagram and Voltage Chart
12
SY PR
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Key features

70 watts RMS output at 4 ohms load (per channel)
Frequency response within 1 dB, 10 to 60 KHz
Total Harmonic Distortion less than 0.1% (typically 0.03%)
Damping Factor greater than 150 with 8-ohm load
Instantaneous overload recovery
Two full-wave power supplies (separate B+ and B-)
Complementary-symmetry configuration
Direct-coupled design (except input network)
Slow turn-on characteristic for system stabilization
Overload indicator lamps (DS101, DS102)

Frequently asked questions

To convert, you need to install a threaded insulated terminal, secure it with a screw, connect the black/white and black/green transformer leads together at this terminal, and then change the fuse to a 1-1/2A, AGC or 3AG type.

The amplifier delivers 70 watts RMS at 4 ohms, 60 watts RMS at 8 ohms, and 40 watts RMS at 16 ohms per channel, across the frequency range of 20 Hz to 20,000 Hz.

To adjust D-C balance, connect a shorting plug to the INPUT, set a VTVM for zero center, and connect its leads to the loudspeaker terminals. With 120V line power applied, adjust potentiometer R19 (located under the access cover screw) until the VTVM indicates a zero center scale.