Shure Incorporated
222 Hartrey Avenue
Evanston IL 60202-3696 U.S.A.
T Wireless System
SERVICE MANUAL CHANGE NOTICE
T4 DIVERSITY RECEIVER
Changes and corrections have been made to the Service Manual for the T4 Receiver. To update your Service
Manual, remove the pages identified in the tables below and replace them with the pages attached to this
Change Notice. Note that there are no changes to pages not specifically identified in the tables below.
T4 RECEIVER SERVICE MANUAL REVISION HISTORY
Release
Part Number
Date Code
Color
Original
25A1020
QG
White
Revision 1
25B1020
SB
Pink
Revision 2
25C1020
SI
White
Revision 3
25C1020
TF
White
Revision 4
25C1020
CC
White
Revision 5
25C1020
EA
Red
CHANGES EFFECTIVE JANUARY 13, 2005
REMOVE
these pages from the
T4 Service Manual
INSERT
these new Revision pages into the
T4 Service Manual
21 & 22
21 & 22
E1999, Shure Incorporated
25–1020–1 (EA)
Printed in U.S.A.
®
Service Manual
25C1020 (EA)
T4 Diversity Receiver
Characteristics
General
This manual tells how to service and align the Shure T4 Diversity Receiver
(Figure 1). This single-channel, crystal-controlled unit operates within the
169 MHz to 238 MHz VHF-FM band.
Á
Á
ÁÁÁÁÁÁÁÁÁÁ
ÁÁ
Á
Á
ÁÁÁ
Á
ÁÁ
ÁÁÁÁÁÁÁÁÁÁ
ÁÁÁÁ
ÁÁ
ÁÁÁ
ÁÁ
ÁÁ
ÁÁ
Á
ÁÁÁÁÁÁÁÁÁÁ
Á
Á
Á
ÁÁ
Á
Á
Á
Á
ÁÁ
Á
ÁÁÁ
Á
ÁÁÁÁÁÁÁÁÁÁ
ÁÁ
1
2
DC INPUT
T4G
SQUELCH
MIN
MAX
12-18 VDC
9
1
2
DC INPUT
SQUELCH
T4V
3
12-18 VDC
MIN
MAX
3
4
5
6
7
8
Figure 1. Controls and Connectors
1. “DC Input” jack
6. “Audio Peak” LED
2. Squelch control
7. Volume control
3. Antennas
8. Audio “Output” (1/4Ȃ phone
jack)
4. “Power” LED
9. “Balanced Low Z” audio output (XLR)
5. “Diversity” LEDs
E1999, Shure, Inc.
Printed in U.S.A.
25C1020 (EA)
Service Note: Shure recommends that all service procedures be performed
by a factory-authorized service center or that the product be returned directly
to Shure Brothers Inc.
1
Characteristics
Shure T4 Diversity Receiver
Circuit Description
The Shure Model T4 is a single-conversion superheterodyne diversity FM
receiver operating in the 169–238 MHz band. It is intended for use with the
matching Shure T Series wireless transmitters.
RF Stages
Two complete, independent RF sections provide diversity reception. Signals
enter via the single-element, quarter-wave antennas.
Channel A: The signals pass through a double-tuned filter (L3 and L4) before entering MOSFET amplifier Q1. The output of this stage is double-tuned by
L5 and L6, which also provide impedance-matching to Gate 2 of GaAs MESFET
(gallium arsenide metal semiconductor field effect transistor) mixer Q3. Gate 1
receives the local oscillator signal from transistor Q5. A third-overtone quartz
crystal in the 50–70 MHz range provides frequency control. The collector circuit
of the oscillator is tuned by L8 to the third harmonic of the crystal (160–230 MHz)
to provide the proper injection frequency for a 10.7 MHz intermediate frequency
(IF).
Channel B: This channel is identical in design to channel A. The signals
from the antenna pass through a double-tuned filter (L12 and L13) before entering MOSFET amplifier Q6. The output of this stage is double-tuned by L14 and
L15 and fed to Gate 2 of GaAs MESFET mixer Q8. Gate 1 receives the local oscillator injection from buffer transistor Q4, which is tuned by L7. The buffer stage
helps isolate the diversity channels from one another by preventing crosstalk
through the common local oscillator section.
IF and Audio-Detection Stages
Channel A: L2 tunes the output of mixer Q3 to 10.7 MHz before the signal
enters ceramic filter FL3. Transistor Q2 provides IF amplification to make up for
the losses in the filters. After passing through a second IF filter, FL2, the signal
enters amplifier/detector U1. The detected audio from pin 6 is amplified by
U105C.
Channel B: L11 tunes the output of mixer Q8 to 10.7 MHz before the signal
enters ceramic filter FL6. Transistor Q7 provides IF amplification before the signal
passes through the second ceramic filter, FL5, and enters amplifier/detector U2.
The detected audio from pin 6 is amplified by U108B.
Noise-Operated Squelch
A noise-operated squelch system provides both diversity-channel selection
and muting. Noise signals are obtained from the additional detector outputs at
pin 7 of U1 and U2.
Noise Signals
Channel A: The squelch level control (R16) adjusts the noise signal from U1
before it is amplified by U105A. Active high-pass filter UI05D removes audio
components that could cause false triggering. The noise is then rectified by D101
and smoothed by C111 to provide a dc voltage that varies with the amount of
noise present on the detected signal.
Characteristics
2
25C1020 (EA)
Shure T4 Diversity Receiver
Channel B: This follows an identical scheme: noise signals from U2 are adjusted by squelch level control R41 before being amplified by U108C, filtered by
U108A, rectified by D107, and smoothed by C140.
Comparator Circuits
U106C and U106D compare the dc noise signals from the two channels.
When these signals are comparable, U106C and U106D direct analog switches
U103C (Channel A) and U103B (Channel B) to allow both channels to pass
through. The signals from each channel are correlated while the noise is uncorrelated, which makes possible a theoretical signal-to-noise improvement of 3 dB.
When the dc noise signals are not comparable, the channel with less noise is
chosen.
U106A imposes an additional criterion on Channel A, and U106B does the
same for Channel B. Each channel’s dc noise voltage is compared to a threshold
set by user-adjustable R112 (Squelch). A channel whose noise exceeds this
threshold is squelched. If both channels exceed their thresholds, the audio output of the receiver is squelched. Squelching is accomplished by tying together
the outputs of U106A and U106C (Channel A) or U106B and U106D (Channel
B). These outputs also control the yellow “Diversity” status indicators. Comparator U102 provides additional attenuation in the squelched state by shutting off
compandor U3.
Audio Output
The audio signals from the two channels pass through analog switches
U103C and U103D, are buffered by U109A, and enter U3, which provides a 2:1
logarithmic expansion. An additional IC amplifier (U109D) operates in conjunction
with U3 to provide a lower noise floor. The output of this stage passes through
the Volume control (R126) to the “Output” connector (J101). A bridging amplifier
formed by U109B and U109C provides the “Balanced Low Z” output.
“Peak” LED
This red indicator warns the user when the transmitter deviation is approaching the limit of 15 kHz. This function is implemented by a window comparator
(U102C and U102D) and a pulse stretcher (U102B) that makes short transients
more visually apparent.
Power
The green “Power” LED indicates when the external power converter (or a
battery pack) is supplying power to the receiver. The circuitry operates normally
with an input of 12–18 Vdc. D10 provides reverse polarity protection, and U101
supplies voltage regulation. The “Dc Input,” audio “Output,” and “Balanced
Low Z” output connectors are filtered to prevent local oscillator radiation from the
cables.
25C1020 (EA)
3
Characteristics
Shure T4 Diversity Receiver
Notes
Notes
4
25C1020 (EA)
Shure T4 Diversity Receiver
Preliminary Tests
Listening Tests
Before disassembling the unit, operate it to determine whether it is functioning normally. First and most important: Review the customer’s complaint (if available) and focus your tests on the problem. If this proves inconclusive or you want
somewhat more extensive checks, perform the following functional tests.
Functional Tests
The following tests require partial disassembly of the unit:
RF Test
The following is the best “fast” test of a receiver’s RF performance. A receiver that passes this test can be removed from the list of suspects for any “dropout” or “range” problem.
Initial Set-up
1. Set the receiver’s Squelch control to its middle position and the Volume
control to its maximum position.
2. Set the RF signal generator to the receiver’s frequency.
3. Remove the receiver’s antenna (see “Disassembly,” page 7). Plug the
BNC end of the 50 Ω test cable into the RF signal generator. Tack-solder
the cable’s center conductor to the receiver’s antenna input (TPA1 or
TPB1), and the shield to a ground plane as close as possible to the antenna input (TPA2 or TPB2).
Test
1. Connect power to the receiver and turn it on.
2. Verify that the unit unsquelches with RF signals greater than –89 dBm.
3. When the unit unsquelches, verify that the “Diversity” LED glows.
Audio Tests
Initial Set-up
1. Set the RF generator as follows:
Level: –60 dBm
Deviation: 15 kHz
Modulation: Ext
2. Set the audio analyzer as follows:
Amplitude: 1.4 Vrms
Frequency: 1 kHz
3. Using a 3.3 kΩ load, connect the receiver’s unbalanced audio output to
the input of the audio analyzer, and engage the 400 Hz and 30 kHz fil-
25C1020 (EA)
5
Preliminary Tests
Shure T4 Diversity Receiver
ters. The receiver’s Volume control should still be in its maximum position.
Tests
1. Verify the following receiver measurements:
S
Audio level is 400 mVrms, "90 mV. Record your measurement as a
reference level for the next two steps.
S
Thd is <0.75%.
2. Change the audio analyzer’s frequency to 100 Hz, and disengage the
audio analyzer’s 400 Hz filter. Verify that the receiver’s unbalanced audio
output is within +2 dB, –1 dB of the reference level recorded in step 1.
3. Set the audio analyzer’s frequency to 10 kHz. Verify that the receiver’s
unbalanced audio output is –7.5 dB to –10.5 dB of the reference level
recorded in step 1.
4. Model T4V only: Place a 150 Ω load across the receiver’s balanced output, then connect this output to the audio analyzer. Verify that the output
is 65 mVrms, "15 mV. Remove the 150 Ω load.
5. If you are finished testing the receiver, remove the test cable and reinstall the antenna (see “Reassembly,” page 8).
Units that Pass
If the receiver passes these tests, then it is functioning as expected and
shouldn’t require alignment. If you did not use the customer’s microphone transmitter for these tests, check it for proper operation. If it also checks out of it it was
not sent in with the receiver, inform the customer that the product has retested
within specifications.
Preliminary Tests
6
25C1020 (EA)
Shure T4 Diversity Receiver
Disassembly and Assembly
To access the printed circuit (pc) board, disassemble the receiver.
CAUTION
Observe precautions when handling this static-sensitive device.
Disassembly
1. Disconnect all power to the receiver.
2. Collapse the antennas and rotate them until they lie flat against the case.
Place the receiver upside down. Remove and set aside the four screws
securing the bottom of the case (Figure 2).
Case
mounting
screws
Case
mounting
screws
Volume knob
Antenna
mounting
screw
Antenna
mounting
screw
Figure 2. Bottom View of Case
3. Place the receiver in its normal operating position and rotate the antennas to their vertical positions. Note that an adhesive-backed nameplate
at the at the rear of the unit holds the upper and bottom parts of the case
together. To open the case, carefully separate the upper part from the
bottom part at the front of the unit. Carefully swing the bottom part of the
case away until the two halves are at a 90° angle, to allow removal of the
circuit board and antennas (Figure 3).
4. After the circuit board has been removed, pull off and retain the Volume
knob.
25C1020 (EA)
7
Disassembly and Assembly
Shure T4 Diversity Receiver
Antenna
Case top
Circuit
board
É
É
Case bottom
Volume knob
Mounting screw
Figure 3.
Reassembly
1. Slide the Volume knob back on: note how it is keyed to the flat part of the
shaft.
2. Rotate the antennas to their vertical positions. Place the pc board, component-side up, inside the top half of the case: after feeding the antennas through their holes, make sure the notches in the case align with the
Volume knob, the LEDs align with the holes in the upper half of the case,
and that the board is fully seated on the studs.
3. Swing the two halves of the case together until they snap in place.
4. Rotate the antennas until they lie flat against the case. Turn the receiver
upside down and secure the assembly with the four screws removed
earlier (Figure 2, page 7). Check that the Volume knob rotates freely.
Antenna Replacement
The antennas can be replaced without disassembling the case. Rotate the
antenna you are replacing to its vertical position, collapse it, and remove the
mounting screw through its access hole in the bottom of the case (Figure 2). Insert the new antenna and start the screw from the bottom, leaving it loose
enough for you to rotate the entire antenna between your fingers. Rotate the antenna in this way as you lightly press it into the case until you feel the base seat
in the slot of the bracket on the pc board. Tighten the screw.
Disassembly and Assembly
8
25C1020 (EA)
Shure T4 Diversity Receiver
Service Procedures
Reference Material
The Shure Wireless System T Series User’s Guide provides a description of
the unit as well as operating instructions, troubleshooting suggestions, and technical data.
Special Equipment and Tools
In addition to the standard items described in the Service Equipment manual,
you will need:
S
a wireless microphone with the same frequency (usually a T1, T2, or
T11) to verify that the receiver is working properly
S
an audio amplifier with a high-impedance input (w10 kΩ) and a
monitor speaker, for listening tests
System Operating Frequencies
Each receiver’s circuit board has a resistor next to the group letter (A–H,
J–L) that identifies the range of frequencies on which the receiver can operate
(see Figure 4). Table 1 shows the Group Letter and its associated frequencies.
Note that this chart applies only to T4 receivers.
Table 1
Pc Board Groups
Group
Frequency Range
A 169.000–173.975 MHz
B 174.000–179.975 MHz
C 180.000–185.975 MHz
D 186.000–191.975 MHz
E 192.000–197.975 MHz
F 198.000–203.975 MHz
G 204.000–209.975 MHz
H 210.000–215.975 MHz
J 216.000–222.975 MHz
K 223.000–229.975 MHz
L 230.000–237.975 MHz
Tables 2 and 3 provide information for identifying the system frequency. The
Crystal Code, together with the appropriate Shure model number, identifies a
specific operating frequency for transmitters and receivers. Note that, although a
Crystal Code always designates a specific frequency, it may be used with different Group Letters on other products.
25C1020 (EA)
9
Service Procedures
Shure T4 Diversity Receiver
Table 2
FCC-Approved Operating Frequencies
Group
A
Crystal Code Freq. (MHz)
V
169.445
A
W
171.845
B
CA
176.200
B
CC
177.600
C
CE
182.200
C
CF
183.600
D
CG
186.200
E
CL
192.200
F
CQ
202.200
G
CV
208.200
Table 3
ETSI-Approved Operating Frequencies
Group
Service Procedures
Crystal Code Freq. (MHz)
A
B
B
B
B
B
B
B
B
C
C
C
C
C
D
D
E
F
F
F
F
G
J
AQ
AY
AZ
ZZ
BA
NB
BB
ND
NE
NH
NK
NL
CS
S
NP
NR
NX
NY
NZ
PU
PB
PD
PP
173.800
174.100
174.500
174.500
174.800
175.000
175.000
176.600
177.600
182.000
183.600
184.600
184.800
184.800
189.000
190.600
197.600
198.600
200.350
201.650
203.000
204.600
217.000
J
PR
218.600
J
PS
219.600
L
PV
232.825
L
PX
233.125
L
PY
234.625
L
PZ
237.325
10
25C1020 (EA)
Shure T4 Diversity Receiver
Changing the Frequency
The operating frequency of the T4 Receiver may be changed within a specific group by changing the crystal on the pc board (for group information, see the
preceding section). Check the receiver for proper operation before attempting to
change its operating frequency. After installing the new crystal, perform the alignment procedures. Then run an operational test to ensure the receiver is functioning properly. Finally, update the label to show the new frequency and letter identification code.
Note: To ensure proper operation, obtain the crystal from Shure and verify
that it operates within the frequency range of the pc board. Since crystals are
marked with the nominal oscillating frequency, not with a letter code, you can
use the following equation to determine the frequency at which a receiver will
operate with a given crystal:
Carrier Frequency = (3
nominal crystal freq. in MHz) + 10.71
Alignment
The alignment steps must be done together, as a single, continuous procedure. Before beginning, be sure to do the setup described in the following subsection, “Test Conditions.”
Test Conditions
The following are the standard test conditions for the T4 Receiver:
S
With a #1 Phillips screwdriver, remove the antennas.
S
Load the the unbalanced, audio output (J101) with a 3.3 kΩ resistor.
S
For RF adjustments, connect a 33 kΩ resistor between ground and
the following points:
Channel A: TPA4 (pin 13 of U1)
Channel B: TPB4 (pin 13 of U2)
S
Set the potentiometers as follows:
Volume (R126): Fully CW
Squelch (R112): Midrange
Audio level (R106 and R168): Midrange
Mute level (R16 and R41): Midrange
Test Cable
1. Obtain a 50 Ω coaxial cable for connecting the circuit boards to various
test equipment. (To construct this cable, see “50 Ω Test Cable Assembly”
in the Service Equipment manual.) Refer to Figure 4 for the locations of
the test points, controls, and tuning components.
2. Tack-solder the cable to the pc board as follows:
Channel A: Center conductor to the antenna input (TPA1) and shield to
ground (TPA2)
Channel B: Center conductor to the antenna input (TPB1) and shield to
ground (TPB2)
25C1020 (EA)
11
Service Procedures
Shure T4 Diversity Receiver
Presettings
Most field units should already be tuned closer to the desired settings than
these approximations. However, you may need to preset units when you are
changing the frequency or an RF coil, or when an unskilled person has attempted
to retune them.
Minimum inductance occurs when the core is level with the top of the
can. Turning the core further counterclockwise or even removing it will
not appreciably affect the inductance.
Maximum inductance occurs when the core is about two turns less than
its full clockwise rotation—about 3.2 mm (1/8 in.) below the top of the
can. Never screw the core against the board.
The manufacturer’s setting of the two smaller, IF coils (L2 and L11) is close
to their ideal setting, so you generally would not preset them. For coils L3–L8
and L12–L15, refer to Table 2 or 3 (page 10) to determine where the desired frequency lies within the board’s group. For frequencies near the bottom of a group,
use the maximum-inductance settings; for frequencies near the top of the group,
use the minimum-inductance settings.
Display Check
1. Connect an external 12–15 Vdc supply to the dc input (J103). The green
“Power” LED should glow.
2. Check for 9 Vdc ("0.35) at TP9 (pin 3 of voltage regulator U101).
Test-Equipment Settings
1. Plug into the RF generator the BNC end of the 50 Ω cable you soldered
to the pcb (antenna and ground). Set the generator’s controls as follows:
S
–20 dBm on the receiver’s operating frequency
S
"15 kHz FM deviation with 1 kHz modulation
2. Activate the 400 Hz high-pass and 30 kHz low-pass filters on the audio
analyzer.
Service Procedures
12
25C1020 (EA)
Shure T4 Diversity Receiver
Antenna B
TPB2 TPB1
Group designator
(see Table 1)
U101
D108
C150
XLR audio output
connector (J102)
D109
C145
Note: Used only on
Presenter and Vocal
Artist models
R168
B
U108 L108
Phone jack
!/4-in. (J101)
R41
L12
B
B
C118
C48
Edge of
case bottom
L13
B
Volume control
TPB4
Power input (J103)
L14
U2
Note: Use Shure
PS20 or PS20E
R126
Knob
B
Channel B
L15
B
L11
U109
TPB3
B
TP9
L7
Crystal (see
Tables 2 and 3)
B
U102
“Audio Peak”
(red)
Y100
U3
L8
B
“Diversity” (RF)
(yellow)
A
(On earlier L2
U107 units only.) A
Squelch control
(R112)
TPB7
TPA7
A
L6
Channel A
A
U1
U103
“Power” (green)
L5
TPA4
TPB5
A
U104
U106
TPB6
L107
L4
A
R16
A
TP8
Note: L107 and L108 are
not found on earlier units.
TPA3
C6
TPA5
L3
A
TPA6
R106
U105
A
Antenna A
TPA2 TPA1
Figure 4. Major Components
25C1020 (EA)
13
Service Procedures
Shure T4 Diversity Receiver
Coil Adjustments
Each channel has to be adjusted separately.
A: Channel A RF and IF
1. Disconnect the power to the receiver. Mute Channel B by grounding
TPB7 (pin 14 of U106). Reconnect the power.
2. Adjust the signal generator’s RF output so that you obtain a reading of
approximately 2 Vdc at TPA4. If this is unattainable even with the full –20
dBm generator output, adjust IF coil L8 until you obtain a reading above
2 V. If you cannot get more than 1.25 V, return L8 to its preset position
and adjust coil L2.
3. Adjust coils L2, L8, L3, L5, L4, and L6 (in that order) for maximum voltage at TPA4. Use a hex tuning wrench for all adjustments except L2,
which requires a non-metallic screwdriver (like a Toray driver). Reduce
the generator output as required to keep the signal voltage under 3 Vdc.
Perform the final adjustments with a generator output of approximately
–85 dBm.
Note: For coils other than L2, the “sharpness” of the tuning depends on
the operating frequency within the frequency group. At the upper and
lower edges of a group, a distinct peak may be difficult to observe. In this
case, adjust the core for maximum indication.
B: Channel A Audio
Note: Before making the following adjustments, power up the circuit
board for at least one minute. This allows the FM detector to stabilize.
1. Set the RF signal generator for an output level of –60 dBm, a modulation
of 1 kHz, and a deviation of 15 kHz.
2. Version E and later boards only: With the probe of an ac voltmeter on
TPA5 (pin 8 of U105), adjust L107 for peak output.
3. Adjust R106 for 0 dBu (775 mV), "0.1 dB, at TPA5 (pin 8 of U105).
4. Reset the signal generator to its minimum output level (or “Off”). Check
that both ”Diversity” LEDs turn off.
5. Set the signal generator as follows:
Level: –50 dBm
Ext. Modulation: 50 kHz
Deviation: 15 kHz
Adjust R16 for 1 Vdc ("0.5 Vdc) at TPA6 (the positive end of C111).
6. Turn off the modulation of the signal generator. Set its output to the minimum level, then gradually increase the level until the “Diversity A” LED
turns on. This should occur with an RF input between –102 dBm and
–87 dBm (typically –95 dBm).
7. Disconnect power from the receiver. Remove the jumper from TPB7 and
the RF input from TPA1 and TPA2.
C: Channel B RF and IF
1. Make sure that the RF generator is connected to the antenna input for
Channel B. Mute Channel A by grounding TPA7 (pin 13 of U106).
Service Procedures
14
25C1020 (EA)
Shure T4 Diversity Receiver
2. Connect power to the receiver.
3. Adjust the RF output of the signal generator RF output so that you obtain
a reading of approximately 2 Vdc at TPB4. If this is unattainable even
with the full –20 dBm generator output, adjust IF coil L7 until you obtain a
reading above 2 V. If you cannot get more than 1.25 V, return L7 to its
preset position and adjust coil L11.
4. Adjust coils L11, L7, L12, L14, L13, and L15 (in that order) for maximum
voltage at TPB4. Use a hex tuning wrench for all adjustments except L11,
which requires a non-metallic screwdriver (like a Toray driver). Reduce
the generator output as required to keep the signal voltage under 3 Vdc.
Perform the final adjustments with a generator output of approximately
–85 dBm.
Note: For coils other than L11, the “sharpness” of the tuning depends on
the operating frequency within the frequency group. At the upper and
lower edges of a group, a distinct peak may be difficult to observe. In this
case, adjust the core for maximum indication.
D: Channel B Audio
Note: Before making the following adjustments, power up the circuit
board for at least one minute. This allows the FM detector to stabilize.
1. Set the signal generator for an output level of –60 dBm, a modulation of
1 kHz, and a deviation of 15 kHz.
2. Version E and later boards only: With the probe of an ac voltmeter on
TPB5 (pin 7 of U108), adjust L108 for peak output.
3. Adjust R168 for 0 dBu (775 mV), "0.1 dB, at TPB5.
4. Reset the signal generator to its minimum output level (or “Off”). Check
that both “Diversity” LEDs turn off.
Level: –50 dBm
Ext. Modulation: 50 kHz
Deviation: 15 kHz
5. Set the RF signal generator as follows:
Adjust R41 for 1 Vdc ("0.5 Vdc) at TPB6 (the positive end of C140).
6. Turn off the modulation of the signal generator. Set its output to the minimum position, then gradually increase the level until the “Diversity B”
LED turns on. This should occur with an RF input between –102 dBm
and –87 dBm (typically –95 dBm).
7. Disconnect power from the receiver. Remove the jumper from TPA7 and
the RF input from TPB1 and TPB2.
E: Final Steps
1. If you were unable to align the unit, refer to the “Bench Checks” section,
which follows immediately.
2. When you have finished working on the unit, reassemble it, as described
in the earlier “Reassembly” subsection on page 8.
25C1020 (EA)
15
Service Procedures
Shure T4 Diversity Receiver
Bench Checks
Note: In this section, test points for Channel A are given first, and the corresponding test points for Channel B are enclosed in square brackets.
DC Power
n Check for 9 Vdc (±0.35 Vdc) at TP9 (pin 3 of U101):
S
If the voltage is lower than normal (but not zero): Check for 15 Vdc at the
input of U101 (pin 1), a reversed electrolytic capacitor (C152), or a stage
that is drawing excessive current.
S
If the voltage is zero: Check for solder bridges or shorted foil traces (defective pcb).
S
If the voltage is higher than normal or the other tests prove negative: Replace U101.
n Check for 5 Vdc (±0.25 Vdc) at TP8 (pin 10 of U3).
Tuning
n First check that that the RF signal is being applied to the correct diversity
channel and that the other channel is being muted with the jumper.
n If the voltage reading at TPA4 [TPB4] does not vary when the RF coils are
adjusted, check the operation of the local oscillator. If everything is working
properly, you should obtain a reading of 1–2 Vdc with a –95 dBm RF input
signal, depending upon component parameters and receiver frequency. If
you do not obtain this reading, try the following:
S
With the RF generator turned off, use a spectrum analyzer to measure
the injection level at TPA3 [TPB3] for approximately –15 to –20 dBm.
S
If the preceding level is correct, use a frequency counter to verify that the
local oscillator signal is 10.7 MHz (±.015 MHz) below the operating frequency of the receiver.
Example: To receive 169.445 MHz, the local oscillator frequency
should be 158.745 MHz (±.015 MHz). Crystal Y100 operates at a
third of this frequency, or 52.915 MHz. The nominal crystal frequency, which is stamped on the part, is 3.333 kHz lower
(52.911667 MHz) in this example. This discrepancy arises because
the load reactance of the oscillator is not precisely zero.
n If any of the RF coils will not tune properly, check for frequency-dependent
capacitors that are missing or have the wrong value. If the IF coil will not
tune, check C9 [C52].
n If all the coils tune but the RF signal is low, compare the dc voltages and
components at RF amplifier Q1 [Q6] with those of a properly working unit.
Muting
n With TPA7 [TPB7] connected to ground, the selected diversity channel should
be squelched and the “A” [“B”] LED should be off, whether or not an RF input
Bench Checks
16
25C1020 (EA)
Shure T4 Diversity Receiver
signal is present. If you obtain different results, compare the dc voltages at
U106, U107 (earlier units only), U103, and U105 [U108] with those of a properly working unit, or replace the pc board.
n If the muting circuit works but has insufficient adjustment range, set the RF
generator for a –95 dBm signal and check TPA4 [TPB4] for 1–2 Vdc, as described in the preceding, “Tuning,” subsection. If you get a lower reading,
consider the following:
S
Low RF levels at the input of U1 [U2] will cause inadequate noise at the
output of U105D [U108A].
S
In order for the noise squelch circuit to function, the detector portion of
U1 [U2] must also be functioning properly (see the following, “Audio,”
subsection).
S
If necessary, check the component values and dc voltages (versus those
of a known working unit) of the following:
Noise amplifier U105A [U108C]
High-pass filter U105D [108A]
Audio
n If there is no audio at the output of the receiver:
S
To verify that the receiver is not squelched, defeat the squelch circuit by
rotating R16 [R41] fully CCW. There should be 9 Vdc at TPA7 [TPB7],
and the yellow “A” [“B”] “Diversity” LED should be on.
S
If the preceding test does not yield the proper results, check for a problem in the squelch circuitry (see the “Muting” subsection, immediately
above).
n Next, check pin 6 of U1 [U2] for an audio signal of approximately –15 dBV. If
there is no detected audio:
25C1020 (EA)
S
Check C1 [C44] and the components connected to pins 7–10 of U1 [U2].
S
On earlier units only: Make sure that FL1 [FL4] is an 86A8920 ceramic
discriminator and not an 86A8910 ceramic filter, which is similar in appearance.
S
Check the dc voltages at U1 [U2] against those of a known working unit.
If no other problem is found, replace the IC.
S
If audio is present at pin 6 of U1 [U2] but not at the output of the receiver,
trace the signal through signal amplifier U105C (TPA5) [U108B (TPB5)]
and expander U3/U109D. When measuring at audio TPA5 [TPB5], use a
1 kΩ resistor in series at the test point to prevent loading the amplifier.
S
Check the Volume control (R126) and the components going to the audio output jack (J101).
S
On vocal models, check for a signal at the Low Z microphone-level output, J102. If no signal is present, check U109B, U109C, and associated
components.
S
Check the dc voltages on any stage that is not working properly; then
look for wrong or missing components. Replace the ICs in the faulty
stage if no other problem is found.
17
Bench Checks
Shure T4 Diversity Receiver
n If you cannot set the audio level properly with R106 [R168], make sure that
the other diversity channel is squelched: only one channel should be activated during this adjustment.
n If you can set the audio levels properly for each channel while the other is
squelched, but these levels change significantly when both channels are activated, check U103.
n If the audio level is correct but the unit exhibits high total harmonic distortion
(thd), vary the RF input frequency 20 kHz above and below the operating
frequency. If the thd drops to an acceptable level, check the local oscillator
frequency. If it is within specifications, repeak the quadrature coil, L107
[L108], for maximum ac output at TP5 [TP8] (see step 1 of “Channel A Audio,” page 14 [step 1 of “Channel B Audio,” page 15]). On earlier units only,
which do not have L107, replace ceramic discriminator FL1 [FL4].
n If the audio circuitry works properly but the red audio peak LED either fails to
light when the standard test signal is applied or remains on when there is no
modulation, check the dc voltages at U102B, U102C, and U102D against
those in a known working unit. Also check the peak LED itself. Replace any
defective components.
Bench Checks
18
25C1020 (EA)
Shure T4 Diversity Receiver
Notes:
25C1020 (EA)
19
Notes:
Shure T4 Diversity Receiver
Replacement Parts and Drawings
On the next page, the parts are listed according to the designations from the
pc board (see Figure 5, page 25) and the schematics at the end of this manual.
Parts shown on the circuit diagram and not listed below are available through
electronic-parts distributors.
On the pages following the parts list are the drawings of the printed circuit
boards and the schematics.
Product Changes
This section briefly describes significant changes to the T4.
Op Amps: The older part for U105, U108, and U109 (manufactured by Raytheon) was replaced. No other component changes were involved.
“E” Revisions: These revisions of the pc boards temporarily changed the IF
detector, deleted U107, changed a number of resistors and capacitors, made
eight coils and a resistor frequency-dependent, and changed Q3 and Q8 from
bipolar mixers to GaAs MESFET (gallium arsenide metal semiconductor field-effect transistor) mixers.
FM Detector: A temporary shortage of the Sanyo chip caused the temporary
substitution of a Harris FM detector. It used two additional resistors, R174 and
R175. Should you replace the Harris detector with the Sanyo unit, be sure to remove those two resistors.
Frequencies: The “G” version of the pc board introduced many new European frequencies, five additional board groups (E–J), and a consequent reassignment of some frequencies to different board groups. The revised board received both some component changes and an altered layout.
Quadrature Coil: The extensive changes on the “G” pc boards, referred to
in the preceding paragraph, included the replacement of ceramic discriminators
FL1 and FL4 with quadrature coils L107 and L108.
Test Points: On earlier versions of the pc boards, the test points were designated as “TP1A,” “TP1B,” etc.; on newer boards, the designations are “TPA1,”
TPB1,” etc.
“J” Frequency Code: Starting in the summer of 1997, T Series transmitters
and receivers tuned to 175.000 MHz have been labeled as “BB” rather than “J.”
The change was made to avoid confusion with the different meaning of the “J”
designation in the LX88 and ELX88 units. It is only a labeling change; the units
are physically the same.
“L” Frequencies: The “F” pcb assembly mainly addresses the addition of a
new “L” group with new European frequencies. There were also a number of minor changes to capacitors, partly small corrections, mainly adaptations to simplify
parts procurement and stocking.
Replacement Parts and Drawings
20
25C1020 (EA)
Shure T4 Diversity Receiver
Parts Designations
The following comments apply to the parts list and the schematic:
Resistors: All resistors are surface-mount with 1/10 W rating and 1% tolerance.
Capacitors: Unless otherwise noted, non-polarized capacitors are surfacemount NPO dielectric types with a 100 V capacity and a 5% tolerance, and polarized capacitors are tantalum types.
Table 1
T4 Hardware Replacement Parts
Reference
Designation Description
Shure Part No.
A1 Printed Circuit Board Assembly
90_8550F
[In the underlined space, insert the
proper Group Code-Letter from
Table 2 or 3, page 10.]
E1 Antenna
95A8320
K1 Case Screws, Antenna Mounts & Antenna
Screw Kit
RPW612
Case Screw
30C1245A
Antenna Mount Bracket
53A8322
Antenna Screw
30C1208A
Hardware Kit
90VY1371
MP1 Case (top)
65B8198
MP2 Case (bottom)
65A8199
MP3 Knob (for Volume control)
65B8235
MP4 Screw, Hi–Lo, Pan (for case)
30C1245A
MP5 Nameplate, Polycarbonate, Rear (Euro)
39A8368
MP6 Nameplate, Polycarbonate, Rear (Domestic)
39B8368
Table 2
T4 PCB Replacement Parts
Reference
Designation Description
Shure Part No.
C6, 48 Capacitor, Electrolytic, 470uF, 16V, 20%
86S629
C105,114,144, Capacitor, Electrolytic, SMD, 10uF, 35V,
149,151,153 20%
151BF106MC
C111,116,127, Capacitor, Electrolytic, SMD, 1.0uF, 50V,
132,140,141, 10%
156
151BG105KB
C118,145,150 Capacitor, Electrolytic, 47uF, 63V, 20%
86BE629
C129 Capacitor, Electrolytic, SMD, 4.7uF, 35V,
20%
151BF475MB
C152 Capacitor, Electrolytic, SMD, 100uF, 16V,
20%
151BD107MD
25C1020 (EA)
21
Replacement Parts and Drawings
Shure T4 Diversity Receiver
D101,107,110, Diode, Signal, Switching, SOT–23, 100VDC
111,112,113 (MMBD7000L)
184A08
D108, 109 Rectifier, Silicon, 140VDC
184A20
FL2, 3, 5, 6
86A8910
Ceramic Filter, 10.7MHz
J101 Phone Jack, Stereo, Right Angle, 1/4-inch
95A8329
J102 XLR connector (Vocal units only)
95A8400
J103 DC Power Jack
95A8328
L1,10,101,102 Ferrite Bead, SMD 805, 600 OHM
,103,104,105,
106
L2, L11 If Coil, 4.7uH
162A12
82A8005
L7, 8 Tunable, 10 mm, RF Coil, Red, 45nH
L9 Inductor, SMD 1008, .22uH (220nH)
L107, 108 Quadrature Coil, 10.7MHz
82A8003
162C06
82A8004
Q1, 6 MOSFET (metal-oxide-semiconductor fieldeffect transistor) SOT–143, (3SK131)
Q2, 4, 5, 7 Transistor, UHF/VHF, RF, SOT–23, NPN,
(MMBTH10L)
Q3, 8 Amplifier, 2 Gate, Hi Gain, Lo Noise, SOT143
(3SK177)
R16, 41, 106, Potentiometer, Linear Taper 5 kΩ
168
183A23
183A03
183A12
46C84
R112 Potentiometer, Linear Taper, 100 kΩ
(Squelch)
46A8008
R126 Potentiometer, Log Taper, 10 kΩ (Volume)
46A8046
U1, U2 Integrated Circuit, FM IF, SO–16 (LA1235)
86A8877
U3 Compandor, SOL–16 (SA571D)
U101 9 V Regulator (MC7809CT)
188A01
86A8944
U102, 106 Comparator, Quad, Low Power, SO–14
(LP339M)
188A123
U103 Switch, Multiplexer, Quad, SO–14
(HEF14066)
188A19
U104 LED Bar, Green/Yellow/Yellow/Red
95A8519
U105,108,109 Quad Op Amp, SO–14 (MC33179D)
Y100 Crystal
188A49
40_8003A
[In the underlined space, insert the
appropriate Crystal Code from
Tables 2 and 3, p. 10]
Note: The tables on the following pages list frequency-dependent parts.
Replacement Parts and Drawings
22
25C1020 (EA)
Shure T4 Diversity Receiver
In the following four-part table, “Grp” is the board’s frequency group, and “Desig” is the number of the
resistor that designates the Group Number. The parts are listed across the tables in alphanumeric order.
All capacitor tolerances are in picofarads.
Table 3
Frequency-Dependent Parts I
C8, C51
C10
C11
C12, C56
C17
C18
A R210
Not used
1 pF (0.1)
12 pF
18 pF
15 pF
Not used
Grp Desig
B R211
1 pF (0.1 )
Not used
12 pF
15 pF
12 pF
1.8 pF (0.1)
C R212
Not used
1 pF (0.1)
10 pF
15 pF
12 pF
1 pF (0.1)
D R213
1.8 pF (0.1)
NA
10 pF
12 pF
12 pF
Not used
E R214
1 pF (0.1)
1 pF (0.1)
20 pF
12 pF
10 pF
1 pF (0.1)
F R215
Not used
Not used
20 pF
12 pF
10 pF
Not used
G R216
Not used
Not used
18 pF
10 pF
10 pF
Not used
H R217
1 pF (0.1)
1.8 pF (0.1)
15 pF
8.2 pF
8.2 p
F
1 pF (0.1)
J R218
1 pF (0.1)
1.8 pF (0.1)
15 pF
18 pF
15 pF
1.8 pF (0.1)
K R219
Not used
1 pF (0.1)
15 pF
18 pF
15 pF
1.8 pF (0.1)
L R220
1 pF (0.1)
1.8 pF (0.1)
12 pF
15 pF
15 pF
Not used
Frequency-Dependent Parts II
Grp C19, C63
C20
C21
C33, C36
C40
C42
C54
A 56 pF
12 pF
NA
15 pF
20 pF
20 pF
1 pF (0.1)
B 56 pF
10 pF
1 pF (0.1)
15 pF
20 pF
20 pF
NA
C 56 pF
10 pF
NA
12 pF
20 pF
20 pF
1 pF (0.1)
D 56 pF
8.2 pF (0.25)
1 pF (0.1)
12 pF
20 pF
20 pF
NA
E 56 pF
8.2 pF (0.25)
1 pF (0.1)
10 pF
20 pF
20 pF
1 pF (0.1)
F 56 pF
8.2 pF (0.25)
NA
10 pF
20 pF
20 pF
NA
G 47 pF
6.8 pF (0.25)
NA
8.2 pF (0.25)
20 pF
20 pF
NA
H 47 pF
5.6 pF (0.25)
1 pF (0.1)
10 pF
20 pF
20 pF
NA
J 56 pF
15 pF
1 pF (0.1)
6.8 pF (0.25)
10 pF
10 pF
NA
K 56 pF
15 pF
NA
6.8 pF (0.25)
10 pF
10 pF
1 pF (0.1)
L 56 pF
12 pF
1.8 pF (0.1)
5.6 pF (0.25)
10 pF
27 pF
1 pF (0.1)
25C1020 (EA)
23
Replacement Parts and Drawings
Shure T4 Diversity Receiver
Frequency-Dependent Parts III
Grp C55
C60
C64
C61
C65
C77, C78
A 12 pF
15 pF
1 pF (0.1)
12 pF
Not used
3.3 pF (0.1)
B 12 pF
15 pF
Not used
10 pF
1 pF (0.1)
3.3 pF (0.1)
C 10 pF
12 pF
1.8 pF (0.1)
10 pF
NA
1.8 pF (0.1)
D 10 pF
12 pF
1 pF (0.1)
8.2 pF (0.25)
1 pF (0.1)
1.8 pF (0.1)
E 20 pF
12 pF
Not used
8.2 pF (0.25)
1 pF (0.1)
1 pF (0.1)
F 20 pF
10 pF
1 pF (0.1)
8.2 pF (0.25)
Not used
1 pF (0.1)
G 20 pF
10 pF
NA
6.8 pF (0.25)
Not used
1 pF (0.1)
H 18 pF
8.2 pF (0.25)
1 pF (0.1)
6.8 pF (0.25)
Not used
1 pF (0.1)
J 18 pF
18 pF
Not used
15 pF
1.8 pF (0.1)
3.3 pF (0.1)
K 15 pF
15 pF
1.8 pF (0.1)
15 pF
1 pF (0.1)
3.3 pF (0.1)
L 12 pF
15 pF
Not used
12 pF
1.8 pF (0.1)
3.3 pF (0.1)
Frequency-Dependent Parts IV
L3, L4, L6,
L12, L13, L15
R24
R26
A 82A8003
82A8003
1.82 kΩ
24.9 kΩ
Grp L5, L14
B 82A8003
82A8003
1.82 kΩ
24.9 kΩ
C 82A8003
82A8003
1.82 kΩ
24.9 kΩ
D 82A8003
82A8003
1.82 kΩ
24.9 kΩ
E 82C8003
82A8003
1.82 kΩ
24.9 kΩ
F 82C8003
82A8003
1.82 kΩ
24.9 kΩ
G 82C8003
82A8003
1.82 kΩ
24.9 kΩ
H 82C8003
82A8003
1.82 kΩ
24.9 kΩ
J 82C8003
82C8003
1 kΩ
12.1 kΩ
K 82C8003
82C8003
1 kΩ
12.1 kΩ
L 82C8003
82C8003
1 kΩ
12.1 kΩ
Replacement Parts and Drawings
24
25C1020 (EA)
1 TPB5
TPB2
TPB1
1
TPB4
1
1
TPB3
TP9
1
1
TPA3
TPB7
1
TPA7
TPA4
1
TPB6
TPA5
TP8
TPA6
1
TPA1
TPA2
Shure T4 Diversity Receiver
Figure 5. T4 Receiver Pc Board, Component Side
25C1020 (EA)
25
Replacement Parts and Drawings
Replacement Parts and Drawings
26
TP1A
TP2A
TP7A (U106, Pin 13) If 9 Vdc, Channel is ”ON”
TP5A
TP4A
TP5B
TP7A
TP3A
TP9
TP3B
TP4B
TP1B
TP6B (Positive end of C40) 1 Vdc
TP7B (U106, Pin 14) if 9 Vdc, Channel is ”ON”
TP6A (Positive end of C111) 1 Vdc
TP2B
TP5B (U108, Pin 7) Audio
TP5A (U105, Pin 8) Audio
TP7B
TP4B (U2, Pin 13) RF Alignment
TP6B
TP3B RF Test Point
TP4A (U1, Pin 13) RF Alignment
TP9 (U101, Pin 3) 9 Vdc
TP2B 50 Ω Input Cable
TP3A RF Test Point
TP8
TP6A
TP1B 50 Ω Input Cable
Channel B
TP2A 50 Ω Input Cable
TP8 (U3, Pin) 5 Vdc
TP – Test Points
TP1A 50 Ω Input Cable
Channel A
Shure T4 Diversity Receiver
Figure 6. Earlier Version of T4 Receiver Pc Board, Side 1
25C1020 (EA)
N27
Channel A
C4
.001
A101 TPA1 C8
N12
N24
N19
*
C13
C12
C77 N87
1
53A8322
18 pF* 1 pF 3.3 pF*
C19
1 L3 L4 1
56 pF*
3
3
4
4
TPA2
82A8003
R1
49.9k
R6
49.9k
9V
N4
N7
R7
33.2
N6
C7
0.5 pF
N10
Q1 2
N15 C9 N16 DOT
Q3 N14 R9
C14 N21 3 2 D
1 3
D
N11
G2 3
1 82A8003* 4
C10
33.2
C11
47 pF
N20 G1
3
1.8 pF* 12 pF*
3 N23
3
G1
183A12
2
150
pF
4
1
4
C15
3SK131/V12 4 1 S
4 R22 S N29
C17 C18
L2 6
R14
270 pF
183A23
L5
L6 1
15 pF* * TPA3
N26
20k
C26 C165 7
9V 100 N27
1 8
R19
C22
9V
C20 C21 R17
C24
.047 150 pF
*
100
.001
100
N31 R20
12 pF*
R15
.001
20k
100
C29
N202
.047
9V
R5
1.82k
N13
86A8910
FL3
Ceramic
Filter
C2
.047
N5
L1
162A12
R3
392
DOT
3
13
1
Q2
FL2
183A03 2 86A8910
2 N22
R11
Ceramic
825 R13
Filter
10
N30
R18
C25
499
.047
C3
.047
N17
1
2
4 L107 82A8004
3
1
6
N9
N2
11
8
R4
10k
9
10
N3
R8
4.99k
3
+
C6
470 µF
16 V
C5
.047
15 N18
U1
86A8877
C16 N25
7
LA1235
.01 R16
FM Detector
N28
C30
14
5k
150 pF
2
5
13 6
N32
12 N33
16
4
TPA4
R174**
C28
N36
4.99k
.047
C27
.047
C31 Audio
.001
R12
332
C23
.047
N8
8
CW
Muting
N34
L8
C76
C75
.001
82A8003
R24 N39
.001
N38 R23
4
C33
3
1.82k
C32
1.82k
C36
15 pF*
1
10 pF
R172
15 pF*
C37
R52 N86 49.9k
N42
.001
R25
3
N40
R51
N43 N41499
49.9k
N89
499 N85
C39
1
3
Q4
R173 Crystal
10 pF
N44 1
Q5 183A03
Quad Coil
183A03 2
24.9k
N46
L108
C40
2 N45
82A8004
R27
R26
Y100
20
pF
C41
R28
2
24.9k
1.82k
4
C43
xxMHz 40-8003
33 pF
499
L10 N51
C42 N47 .001
N75
9V
3 1
6
C164
162A12
47 pF*
L9
N50
I210 N210 R210 N212
R31
33 pF
C45
R30
C46
Channel B
A
I212
220 nH
N52
49.9k
.047
.047
10k
+ C48
10k
I211 N211 R211 N213
C47
R32
R44
R33
B
I213
R34
.047
R35
11
392
9
8
10
C49
470
µF
4.99k
10k
N203
1.82k
N55
20k
1
N54 DOT
R212
49.9k N53 N57 R36
.001
16V
C50
U2
33.2
N56
C
N59
TPB3
15 N58
N60
1 3
3
A102 TPB1 C51 N61
C52
R38
N64
N65
10k
DOT
1
N62
2D
R39
Q7
2 N63
L14 0.5 pF L15
N73
FL5
86A8877
R213
C53 N66
1 3
C58
7
*
G2
1
4
D
G2
332
C55
183A03 2 Ceramic
D
C57
C78
LA1235
Q6 C54
3
C56
Q8 33.2 1 47 pF
CW
10k
12pF* 3
3
1
N67 N88 N68
2 N70
G1 3
FL6
R40
3
N71
.01
4
2
150
pF
1.8pF*
Filter
FM Detector
R41
N72
C73
N75 4
3SK131/V12 4 1 S
825 R42
C59
G1 4 1 S 183A12 L11 6
Ceramic
53A8322 18 pF* 1 pF 3.3 pF*
1 C60 C61
I214 N214 R214 N216
Muting
86A8910
5k
150 pF
270pF
183A23
R43 82A8003* 82A8003
I216
E
R50
2
4
5
13
L12
L13
6
16
C62
12
N76
10
Filter
4
10k
15 pF* *
1
N74
C63
N79
N77
.047
N69 20k
I215 N215 R215 N217
TPB4
86A8910
C71 C166 7 8
9V 100
C64 C65
3
56 pF*
3
3
F
I217
R45
R175**
N80
C66
R46
C68
4
12
p*
1
N78 N83
R47 .047 150 pF N82
C69
TPB2
*
C70
4.99k
100
499
.001
R21610k
C67
9V
.047
.001
100
.047
G
R49
.047
10k
82A8003
C72
14
100
R217
C74
.047
H
5V
.001 Audio
10k
9V
188A49
5
Pin 6 of U1
I218 N218 R218
U103A 1
7
14 10
J
U105B
N36
10k
13
12
R219
C102
U103D
N220
2
K
6
11
188A19
I219 N219 10k
N101
5V .33
188A19
TPA
5
7
188A49
R101 10
N90
R220
L
I220
N102
8
N103
100k
U105C
10k
9
8 9
C105
R103
R102
10 µF
6.81k
U103C
Pin 7 Channel A
35V
N105 N104 40.2k
188A19
C104
+
6
9V
(Pin 2 of R16)
120 pF
D101
CW
9V
R104
N34
R105
N106
N107
1
N108
200k
B Channel Bias
R107
5k
200k
20 mV ref.
TPA6
C110
N110
R108
R106
1M
1
2
N113
150 pF N111
CW R112
C107
C108
R109
N117
N114
R110
N118
N115
1
2
R111
N116
N125
3
20k
U105A
2
100k
R114
5V
33 pF
C111 + 10M
6
10M N171
499 N112 C109 184A08
C112
330 pF C113
100k
N121 3
Mute Drive
R115
49.9k 1.0
R117
188A49
3
150pF
1
.1
N123 5 188A49
R118
R113 50V
150pF
R119 330pF
U102A
100k
200k
1.5k
C163
7 N128 R120 N126 +C114 N127
+ C116
N125
20 mV ref.
4.75k N124 13 4
9V
U109D
9V
R121
7 188A04
1
10 µF, 35V 3 Volume
C118 N132 R125 N133 J101
499
R122
10 10
C158 9V
U105D 14
49.9k
50V
R126 2
6
5V
LP339MX
9V
R123 R171
2.21k
+
C157
R128
188A49
C119
C120
.001
47 µF, 63V C121 3.32k 2 3
10k
12 11
.001
1
R127
6.81k
N136
R129
CW
.1
5
1
R130 .001
3
N135
100k
N134
.0039
1M
R131
R132
TPA7 9V
N137
100k 100V
N139
U106A 2
L101
9V N140
9V
16.5k
4
N138
24.9k
R133
R134
162A12
R139
12
R136 N141
N131
1M
* R137
D110
1k
188A04
* + 9V
R138
1
49.9k
LP339MX
N201
9
1M
C123
3
9V
C124 N143
14
5V
11
2 3 Yellow
*
U102C
U104B
.001
13
8
184A08
9V
6
188A04
U106C
4 95A8519
N146 C126
10
5 16 7 13
2
LP339MX
C161
8
*
R141
1 N145 100k
188A04
188A04 9V
C127
11
R142
U3
R143
R169
N147
.001
+
15 27.4k
C128
LP339MX R145
U109A 1
R144
13
4
3
188A01
1k
12
1 µF,
7
0 N150 2
184A08
U102D
.01
100k
NE
571
D
2
N152
10k
3
10
188A49
N149 U102B
3
50V C129 N155 3
D111
14 N151
N153
Compandor
TPB7
U106B 1
188A04
Pin 7 U2 Channel B
+
7
C130
6
C131
2
10
LP339MX
12
1 4 11
R146
4.7 µF, 35V
Red
188A04
5
.047
100
pF
(pin 2 of R41)
49.9k
9
LP339MX
N158
N157
C159
8 U104D 95A8519
N154
C125
9
R147
N80
.01
+
N160 R148 N161
2
.01
C132
D107
14
N162 30.1k
200k
C136
D112
1
R149
N166 8 U106D
1
9
150 pF
184A08
3
50V
C134
188A04
5V TP8
N165 20k
N167 C135
N168
TPB6
5V U108C 8
C137
LP339MX
33 pF
1
330 pF
.01
C138
R151
R152
3
N170
N171
2
188A49
N164 6
C139
10
R155 +
R154 330 pF
Yellow
499
200k
.1 N173
2
C140
5V
N175
4.75k
D113
U104C 95A8519
184A08
49.9k 1
1
Channel B
N174
9V
5
1
U108A
50V
N200
R156
3
C141
5V
12 188A49
5
C162
Pin 6 of U2 N83
188A49
U103B
2
R150
4
3
49.9k
1
+ 13 4 .001
188A19
1k
U108D 14
50V
C144 N177 R157 N179 C145 N178
C143
184A08
14
N180
9V
13
.33
9V
+
R158 N119 U109C
4 3
5V
47 µF
10 µF 750
R159
L102
TPB
5
C160
L106 162A12
188A49
11
5
N93
R160
C146
12
100k
162A12
.001
63V
N199
5V
35V
N182
68.1
.001
188A49
100k N181 U108B 7
100V
2 3 J102
N176
11
D1
1
6
R162
C147
R161
Output
6.81k N183
.001
R163
68.1
R164
188A49
10
N184
Power
12-18Vdc
D10
100V
N185
40.2k
C149
C150
R165
TP
9
N190
+
N193
100k +
C148
* Leave off R134, R136, C123.
N189
U109B 8
C151
9V
J103
D108
+
R166
L103
750 N191 47 µF
C156
10 µF, 35V
10 µF
L104
+
N188 I
N187
O
N186
2
9
On
first
production:
1
U101
1 N194 120 pF
10k
162A12
63V
35V
1
3
R167
D109
R170
2
50V
R168
162A12
3 - 1
+
C154
1k
+ UA7809C G
N197
R17 = R45 = 49.9Ω
CW
5k
10k N195
C152
C153 86A8944
.001
N198
3
1 Green
R7 = R36 = 33.2Ω
100 µF
N196
10 µF
16V
L105
U104A 95A8519
35V
C40 = 10 pF
I92
C155
2
162A12
.001
**R174 and R175 are only used with the Harris FM Detector.
I91
B Channel Bias
82A8003
4
L7
3
1
T4 Schematic
(from 90-8550E-11)
Channel A
A101 TPA1
53A8322
C4
.001õF
C8*
C12*
C77*
C13
1 pF
1
3
4
* C19
TPA2
1
3
4
R6
49.9ĂkΩ
C7
0.5 pF
R7
33.2ĂΩ
Q1 2
D
G2 3
* C10
G1
3SK131/V12 4 1 S
183A23
* *C21 R17
C20
100ĂΩ
* L3 * L4
*C11
9V R14
100ĂΩ
C24
.001õF
4
3
1
3
4
* L5
C22
.001õF
* L6
C9
R9
DOT
1 3
D
3
33.2
47 pF
3
183A12
2
150 pF G1
4
1
C15
4 R22 S
L2 6
C18
270 pF
* TPA3 20ĂkΩ .047õF C165 1 7 8
R19
9V
C26 150 pF
100ĂΩ
R20
R15
20ĂkΩ
100ĂΩ
C29
.047õF
82A8003
4
L7
3
1
C76
.001õF
R23
R24
1.82ĂkΩ 1.82ĂkΩ
R172
C37
49.9ĂkΩ .001õF
C33*
R52
499ĂΩ 3
C39
10 pF
Q4
183A03 2
R27
1.82ĂkΩ
TPB1
A102
*
C17
1
53A8322
C56*
C63*
TPB2
R35
49.9ĂkΩ
C49
.001õF
C57
*C78
1 pF
4
3
1
* L12
1
3
4
G2
G1 3
3SK131/V12 4
183A23
* *C65 R45
C64
100ĂΩ
L13 *
R36
33.2ĂΩ
2D
Q6 *C54
1S
C68
.001õF
C75
.001õF
R25
49.9ĂkΩ
*C40
24.9ĂkΩ
R26
Y100
xxMHz 40-8003
C55
*
R43
9V 100ĂΩ
1
3
4
0.5 pF
* L14
L15 *
C102
0.33õF
5V
188A49
R101 10
8
100ĂkΩ
U105C
9
R103
R102
6.81ĂkΩ
40.2ĂkΩ
C104
C105 +
10 µF
120 pF
35V CW
C60
*
C43
.001õF
L9
220 nH
4 L107 82A8004
1
6
R8
4.99ĂkΩ
+
C6
470 µF
16 V
C5
.047õF
15
U1
86A8877
C16
7
LA1235
.01õF R16
FM Detector
C30
14
5ĂkΩ
2
5
150 pF
13 6
12
16
4
TPA4
R174**
C28
4.99ĂkΩ
.047õF
C27
.047õF
Audio
C31
.001õF
150 pF
*C61
9V
R44
20ĂkΩ
7
13
6
R34
1.82ĂkΩ
DOT
1
3
DOT
1
Q7
1 3
183A03 2
2
FL6
R40
2
825ĂΩ
C59
Ceramic
R42
270ĂpF
Filter
10ĂΩ
86A8910
R46
C69
499ĂΩ
9V
.047õF
R49
100ĂΩ
9V
U103A 1
188A19
8
U103C
188A19
9V
D101
R33
392ĂΩ
C52
R38
2
D
G2
47 pF
33.2ĂΩ
Q8
3
1 4
G1 4 1 S 183A12 L11 6
R50
20ĂkΩ
C71 C166 7 8
3
R47 .047õF 150 pF
100ĂΩ
C72
.047õF
188A49
U105B
TPA5
R18
499ĂΩ
1
3
CW
Muting
Quad Coil
L108
82A8004
2
4
2
C58
5
2
2
3
C32
10 pF
C66
.001õF
Pin 6 of U1
R11
825ĂΩ
8
R4
10ĂkΩ
8
9
10
11
R51 499ĂΩ
3
Q5 183A03
R28
499ĂΩ
C42*
1
86A8910
FL3
Ceramic
Filter
L8
82A8003
TPB3
4
3
R3
392ĂΩ
3
1
R5
1.82ĂkΩ
1
C50
5V
Pin 7 Channel A
(Pin 2 of R16)
4
3
1
* C36
R173 Crystal
24.9ĂkΩ
C41
33 pF
C164
33 pF
R31
49.9ĂkΩ
C51*
1
Q3 2
C14
9V
Channel B
L1
162A12
C2
C3
.047õF
.047õF
DOT
13
Q2
FL2
183A03 2 86A8910
Ceramic
R12
332ĂΩ
R13
Filter
10ĂΩ
C23
C25
.047õF
.047õF
9V
R1
49.9ĂkΩ
12
2
14 10
7
11
9
6
C45
.047õF
3
L10
162A12
11
1
FL5
Ceramic
Filter
86A8910
R39
332ĂΩ
3
C46
.047õF
3
24
C62
.047õF
C70
.047õF
1
6
R30
10ĂkΩ
9
8
10
U2
86A8877
LA1235
FM Detector
5 12 13 6 16
TPB4
C67
14 .047õF
+ C48
470 µF
16V
C47
R32
4.99ĂkΩ .047õF
15
7
C53
.01õF
R41
C73
150 pF 5ĂkΩ
R175**
4.99ĂkΩ
C74
Audio
.001õF
CW
Muting
A
B
C
D
E
F
G
H
J
U103D
188A19
K
L
I210 R210
I212
10ĂkΩ
R211
I213
10ĂkΩ
R212
10ĂkΩ
R213
10ĂkΩ
I214
R214
I216
10ĂkΩ
I215
R215
I217
10ĂkΩ
R216
10ĂkΩ
R217
10ĂkΩ
I218
R218
10ĂkΩ
R219
N220
I219
10k
R220
I220
10k
I211
9V
*
R105
200ĂkΩ
B Channel Bias
R107
20 mV ref.
1ĂMΩ
1
2
CW R112
R109 C109
C107
C108
R110
1
2
R111
3
2 100ĂkΩ
R114
5V U105A
R113
33
pF
C111
+
6
10M
330ĂpF
499ĂΩ 0.1õF 184A08
10ĂMΩ
C112
3
330 pF
Mute Drive
100ĂkΩ
R115
1õF
R117
188A49
3
C163
1
5 188A49
R118
150ĂpF
49.9ĂkΩ 50V
R119 C113
U102A
100ĂkΩ
200ĂkΩ
1.5ĂkΩ
150ĂpF
R120
7
+ C116
+C114
13 4
20 mV ref.
4.75ĂkΩ
9V
U109D
9V
R121
7 188A04
1õF
10 µF, 35V 3 Volume
14
C118
499ĂΩ
R125
R171
R122
10ĂΩ
C158
J101
U105D
9V
49.9ĂkΩ 2.21ĂkΩ
50V
R126 2
6
5V
LP339MX
9V
R123 10ĂΩ
+
C157
.0039õF R128
C119
10ĂkΩ 1
47 µF, 63V C121 3.32ĂkΩ 2 3
.001õF 100ĂkΩ
12 11 188A49 .001õF
R127
CW
0.1õF R129
5
1
3
R130 .001õF
6.81ĂkΩ
1ĂMΩ
R131
R132 C120
TPA7 9V
100ĂkΩ 100V
U106A 2
L101
9V
9V
16.5ĂkΩ
4
R134
24.9k
R133
162A12
R139
12
R136
N.S.
1ĂMΩ
D110
1ĂkΩ
188A04
R137
N.S.
R138
1
+ 9V
LP339MX
49.9Ăk
9
1ĂMΩ
C123
3
9V
C124 Ω
14
5V
11
2 3 Yellow
N.S.
U102C
U104B
.001õF
13
8
184A08
9V
6
C126 N.S.
188A04
U106C
4 95A8519
10
5 16 7 13
2
LP339MX
C161
8
R141
1
188A04
188A04 9V
C127
11
R142
U3
R143
R169
+
15 27.4ĂkΩ
.001õF
C128
LP339MX R145
U109A 1
R144
13
4
3
188A01
2
1ĂkΩ
12
1 µF,
7
184A08 100ĂkΩ
U102D
.01õF
0ĂΩ
100ĂkΩ
NE
571
D
2
3
10
10Ăk
188A49
3
50V C129
D111
14
3 Compandor
U102B
TPB7
U106B 1
188A04
Pin 7 U2 Channel B
ΩC130
+
7
6
C131
2
10
LP339MX
12
1 4 11
R146
4.7 µF, 35V
Red
188A04
5
.047õF
100 pF
(pin 2 of R41)
49.9ĂkΩ
9
LP
339
MX
C159
8 U104D 95A8519
C125
9
R148
R147
+
.01õF
2
C132
D107
.01õF
200ĂkΩ
C136
30.1ĂkΩ
U106D 14
D112
1õF
R149
8
1
9
150 pF
184A08
3
50V
C134
188A04
5V TP8
C135
TPB6
20ĂkΩ 5V U108C 8
C137
LP339MX
33 pF
1
330 pF
C138
R151
.01õF
R152
3
2
188A49
C139
10
6
49.9ĂkΩ +
R154 330 pF
Yellow
2 200ĂkΩ 499ĂΩ 0.1õF
C140
5V
4.75ĂkΩ
D113
U104C 95A8519
184A08
R155 1õF
1
Channel B
9V
5
1
U108A
50V
C141
R156
3
5V
12 188A49
5
Pin 6 of U2
C162
.001õF
188A49
U103B
2
R150
49.9ĂkΩ
4
3
1õF
+ 13 4
188A19
1ĂkΩ
U108D 14
50V
C144
C145
C143
R157
184A08
9V
13
.33
9V
U109C 14
+
R158
4 3
5V
47 µF
10 µF 750ĂΩ
R159
L102
C160
L106 162A12
11
5 188A49 TPB5
R160 63V C146
12
162A12
100ĂkΩ
5V
35V
.001õF
7
.001õF
188A49
68.1ĂΩ
100ĂkΩ
U108B
100V
2 3 J102
11
D1
1
6
C147
R162
R161
Output
R163
.001õF
6.81ĂkΩ
68.1
R164
10 188A49
Power
12-18Vdc
D10
100ĂV
* FrequencyĆdependent parts: see TableĂ7 near the end of
C149
40.2Ăk
C150
R165
TP
9
+ Ω C148
100ĂkΩ +
U109B 8
C151
9V
the manual.
J103
D108
+
R166
L103
750ĂΩ 47 µF
C156
10 µF, 35V
10 µF
L104
+
I
O
120 pF
2
9
U101
1õF
1
162A12
63V
10ĂkΩ
**R174 and R175 are only used with the Harris FM Detector.
35V
1
R167
3
D109
R170
2
R168
162A12
50V
3 - 1
UA7809C
G
+
C154
1k
+
CW
5ĂkΩ
N.S. (not stuffed): Leave off R134, R136, C123, C126.
10ĂkΩ
C152
C153 86A8944
.001õF
3
1 Green
100 µF
10 µF
16V
L105
U104A
On first production:
35V
I92
C155
2
95A8519
162A12
R17 = R45 = 49.9ĂΩ
.001õF
R7 = R36 = 33.2ĂΩ
I91
C110
150 pF
R108
20ĂkΩ
200ĂkΩ
R106
5ĂkΩ
1
TPA6
B Channel Bias
R104
T4 Schematic
C40 = 10 pF
(from 90-8550F-11)
Ceramic Discriminator
9V
Antenna
TP1A
1
A101
N24
C8
R6
24.9k
18pF*
N19
C13
1pF
C19
56pF*
4
3
1
L3
N87
C77
N20
N6
C20
12pF*
D
2
C11
12pF*
C7
100
C24
.001
N11
0.5pF
N14
TP3A
L6
4
N23
3
1
82A8003
3
4
82A8003
N27
C22
.001
R14
9V
C21
* R17
100
N10
L5
1
499
G2
C10
3SK131/V12 G1 3
1.8pF*
1S
4
183A23 N26
3.3pF*
L4
1
3
4
TP2A
82A8003
R7
N7
Q1
N12
C17
15pF*
183A03
Q3
C18 150pF
*
R15
7.5K
L7
C39
1pF
4
3
1
C33
15pF*
R52
N41
N43
1.0K
Q4
183A03
3
N38
R23
C34
*
N86
332
332
C35
*
L2
R11
FL3
825
2
Ceramic Filter
C15
270pF
64
1
R13
10
C26 N31
.047
C29
.047
C23
.047
3
C1
56pF
2 4 14 5 12 13
N32
TP4A
C28
.047
C27
.047
9V
R20
100
9
R26
Y100
12.1K
xxMHz Crystal
40–8003
4
3
1
3
1
C30 .01
150pF
N85
R28
499
N47
C43
.001
L9
220nH
Ceramic Discriminator
1
N73
TP2B
C51
*
C56
18pF*
C63
56pF*
N59
N67
C57
C78
82A8003
C55
12pF*
N75
R43
9V
100
N56
C50
N60
0.5pF L15
1 L14
4
3
3 N71
4
C60
1
82A8003 82A8003
15pF*
C66
.001
TP3B
C58
C61
*
N69
N63
3
1
183A03
Q8
150pF
R44
7.5K
R38
N76
R47
499
R50
C52
N64
33.2
1
6
2
C71
.047
N65
47pF
4
L11
C59
270pF
N62
86A8910
R40
2 FL6
825
Ceramic Filter
DOT
1 3
78
3
N82
9V
C72
.047
R49
100
N51
1
R42
10
R46
499
N54 DOT
N55
3
1 3
86A8910
Q7
R39
FL5
183A03
332
2
2
Ceramic Filter
N70
N72
C62
.047
N79
C69
.047
C44
56pF
DOT
3 1
R29
287
86A8920
2 FL4
N50
R30
C46
.047
C45
.047
N57
499
Q6
2D
G2
C54
N88
N68 3SK131/V12 G1 3
1.8pF*
4
1
3.3pF*
1pF
183A23 S
N74
L12 L13
1
4
C64 C65
3
3
R45
C68
12pF* *
1
4
100
.001
82A8003
N61
162A03
R33
392
R34
1.82K
R36
N49
L10
9V
R35 N53
24.9k
N34
Audio
C32
1pF
R31
49.9K
C49
.001
Muting
N33
N36
CW
C31
.001
N75
Antenna
A102
TP1B
N25
R16
5K
6 16
N48
Channel B
26.7k
C16
7
Q5
183A03
2 N45
C40
20pF
C42
47pF*
N18
15
+ C6
470uF
16V
R10
N40
N42
R51
1.0K
N44
2
C5
.047
R8
2.21K
10
U1
86A8877
LA1235
FM Detector IC
N28
N30
C25
.047
R18
499
1
332
N9
8
11
L8
82A8003
C36
15pF*
R25
49.9K
1
C41
.001
47pF
3
N8
37.4K
C75
N39 .001
N46
R27
1.0K
N16
DOT
1 3
86A8910
Q2
FL2
183A03
N17
2
2
Ceramic Filter
N22
R12
332
DOT
3 1
86A8920
2 FL1
N3
R2
287
R4
N5
3
78
R22
R24
C37
.001
R5
1.82K
N13
DOT
1 3 86A8910
1
R19
499
9V
82A8003
N15
2
N29
82A8003
C76
.001
C9
33.2
3
N21
1
C14
R9
N2
162A03
C3
N4
C4
.001
*
C12
R3
392
.047
R1
49.9K
N1
C2
Channel A
L1
.047
N27
N52
8
11
1
3
332
9
U2
86A8877
LA1235
FM Detector IC
N77
C70
.047
2 4 14 5
R32
2.21K
10
12 13 6 16
TP4B
N78 C74
C67
.001
.047
15
N58
C47
.047
R37
+ C48
470uF
16V
26.7k
C53 N66
7
C73
150pF
.01
R41
5K
CW
Muting
N80
N83
Audio
37.4K
E
1999, Shure Brothers Inc.
27C1020 (SB)
T4 Earlier Version Schematic
(page 1 of 2)
Pin 6 of U1
N36
N101
TP5A
188A120
10
RC4156M
8
U105 C
9
R103
R102
6.81K
22.1K
N105
N104
C104
C105 +
220pF
10uF CW
35V
N106
N34
C110
150pF
R104
N107
N108
100K
N111 R108
20k
5V
U105 A
3
C107
1
188A120
330pF
R119
4.75k
RC4156M
C113
330pF
N124
C159
.001
6
3
U107 A
7
1
12
11
RC4156M
9V
R135
100K
5V
TP6A
N113
3
2
184A08
R113
49.9K
C109
R109
499
.1
4
9V
C111 +
1.0
50V
R121
49.9K
14
C157
.001
188A120
N114
N134
R107
1M
R110
N117
10M
R117
100K
N125
R122
2.21K
9V
4
U107 B
2
188A04
5
C158
.001
5
N135
R140
100K
11
N144
C125
.01
14
12
N148
U103 D
7
C128
.01
R159
100K
N181 188A120
TP5B
5
RC4156M
U108 B
7
D107
1
C135
N167
188A120 330pF C139
R154
4156M
330pF
4.75k
Channel B
N174
(Pin 6 of U2)
5V
N83
C143
.33
5V
C134
LP339MX
10
7
LP339MX
33pF
2
N170
R152
C138
R151
200K
.1
499
3
2
184A08
N173
1
U108 A
3
TP6B
N168
N171
R155
49.9K
RC4156M
4 188A120
188A04
9
LP339MX
14
U106 D
N166
C137
.01
8
N125
8
LP339MX
C163
14
U107 C
150pF
9
Move 150 pF
close to pin 8
of NE571.
N116
R114 N123
100K
5
C112
150pF
+ C116
1.O
50V
188A04
N201
3
Yellow
N145
9V
R145
100K
24.9k
R139
1.0K
184A08
D101
1
3
2
5V
U104 B
R169
4
1
2
N154
2
D112
184A08
1
100K
184A08
3 D111
TP7B
188A120
2
3
188A04
U109 A
3
RC4156M
C131
100pF
N146 C126
16.5K
R136 N141 *
*
9V
C123 +
*
C124
.001
C114
Volume
N126 +
N127
C118
10uF x 35V
3
10k
2
9V R126
C119
47uF x 63V
1
.1
R129
R130
CW
1M
100K
R120
7
N128
188A120
6
R128
C120
6.81K
.0039
N137
R132
R131
9V
Mute Drive
RC4156M
U109 D
N136
TP7A
1
6
20mV Ref.
R123 R171
10
10
13
188A04
499
9V
R134
R137
49.9K
N143
N140
9V
R133
1M
9
8 6
N164 1
6
U104C
95A8519
5
D101
1
N200
3
2
R150
1.0K
184A08
9V
N175
R156
49.9K
9V
N182
1
L101
162A03
9V
C161
.001
N149
R144
4
10K
C130
.047
3
U102 B
R143
1.0K
N153
2
7
Red
U104 D
8
12
5
188A04
95A8519
R158
N119
100K
12
C162
.001
4
U109 C
N177
C144
R157 N179 C145 N178
N180
+
x
47uF x 63V
L102
10uF 35V 750
162A03
R160
C146
68.1
.001
N176
100V
14
11
RC4156M
C155
3
N139
9V
D1
L105
162A03
N133
2 J101
9V
5V
POWER 12–18VDC
L103
162A03
J103
N186
+
N187
2
3
– 1
162A03
C154
.001
N196
I91
3.32K
R138
1M
188A04
5
C141
188A120
1.0
+ 13
50V
C160
.001
6
11
R162
6.81K
N183
R163
N185
22.1K
C151 +
C148
10uF
35V
220pF
N194
1
2
5K
CW
R168
3
R125
N131
14
U102 C
LP339MX
8
16 7 13
N147 C127
11
15 R141
U3
2
+
12 27.4K
188A01
13
N150
0
1.0 x 50V
N151 U102 D
NE571D
N152
14
Compandor IC
+ C129 N155 3
188A04
10
R146
4.7uF x 35V
4 11 9 10
LP339MX
1
N158
49.9K
N157
R147
C132 +
1.0
30.1k
50V
N162
TP8
5V
*
R142
N132
C121
.001
100V
Yellow
+C140
1.0
50V
4 188A19
5
3
U103 B
10
8
B Channel Bias
5V
3
U106 B
N161
9V
R127
100K
2 N138
U106 C
10
11
100K
U108 C
9V
LP339MX
2
188A19
R148
R118
1.5K
20mV Ref
LP339MX
Pin 7 U2 Channel B
(Pin 2 of R41)
N80 N160
C136
R149
150pF
9
N165 20k
N171
10M
13
9V
R105
200K
1
R112
100K
3
N110
CW
2
N121
U106 A
188A04
4
12
U103 A
9
B Channel bias
R111
188A19 1
N142
188A04
12
LP339MX
D101
N112
U105 D
5V
9V
9V
9V
N118
33pF
R115
200K
13
Note: Net name must be equal at
each B Channel bias point.
1
5K
R106
C108
N115
2
N103
6
Pin 7 Channel A
(Pin 2 of R16)
N102
188A19 8
100K
U103 C
C102
.33
R101
5V
D10
R164
D108
9V
D109
I
O
U101
3
1
G
86A8944 UA7809C
N188
C153 +
10uF
35V
I92
N184 10
TP9
+ C152
100uF
16V
R170
1.0K
N198
1 Green
95A8519
2 U104 A
*Leave off R134, R136, C123
First production assembled with
R17=R45=49.9 ohms and
R7=R36=33.2 ohms
C40=10 pF
100K
C156
1.0
50V
+
U109 B
R166
10K
9
N197
R161
68.1
188A120
R167
8
C149
R165
+
10uF x 35V 750
N195
N193
L106
162A03
N199
2 3 1
C147
.001
100V
C150
N189
47uF x 63V
N190
J102
Output
L104
162A03
N191
10K
RC4156M
.001
E
1999, Shure Brothers Inc.
27C1020 (SB)
T4 Earlier Version Schematic
(page 2 of 2)