Shure uc4 Service Manual

Shure Incorporated
222 Hartrey Avenue
Evanston IL 60202-3696 U.S.A.

UC UHF Wireless System

SERVICE MANUAL CHANGE NOTICE

UC4 DIVERSITY RECEIVER

Changes or corrections have been made to this service manual. Update your service manual by replacing
the pages listed in the table below with the ones attached to this change notice.

CHANGES EFFECTIVE [DATE]

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Revision 1 pages: ALL Revision 2 pages: ALL

Revision 2 pages: 14,15,19,20,21,22,26,27 and 30 Revision 3 pages:14,15,19,20,21,22,26,27 and 30

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attached to this notice

INSERT

SERVICE MANUAL REVISION HISTORY

Release Part Number Date Code

Original 25A1045 RI
Revision 1 25B1045 SB
Revision 2 25C1045 TB
Revision 3 25C1045 TK

E1999, Shure Incorporated

Printed in U.S.A.

UC4 Diversity UHF Receiver

Characteristics

General

The Shure UC4 Diversity UHF Receiver is a microprocessor­controlled single diversity receiver operating in the 692 to 716 MHz and
774 to 862 MHz frequency range. The UC4 is used in mid-level installed
sound, rental, and concert sound applications.

Controls and Connectors

R

A B

1

Service Manual

25C1045 (TK)

2

12

1. Diversity Indicators

2. Squelch Control

3. Rf Level Indicators

4. Audio Level Indicators

5. Low Transmitter Battery Indicator

6. Group Rotary Switch

7. LED Display

8. Channel Rotary Switch

9. Equalization (

Service Note: Shure recommends that all service procedures be performed by a Factory­Authorized Service Center or that the product be returned directly to Shure Incorporated.
Licensing: Operation may require a user license. Frequency or power-output modifica­tions may violate this product’s approvals. Contact your country’s communications authori­ties.

3 4

13 14 15

EQ) Adjustment Controls

Figure 1. UC4 Controls and Connectors

5

16

7

6

10. Level (Volume) Control

11. Power On/Off Switch

12. Power Input Connector

13. Balanced (

MIC/LINE Side Switch

14.

15. Unbalanced (

LOGIC OUT Connector

16.

17. Antenna Input Connectors

8

17

LOW Z) Output Connector

HIGH Z) Output Connector

10

119

E1999, Shure Incorporated Printed in U.S.A.

25C1045 (TK)

Shure UC4 Diversity Receiver

Circuit Description

The audio circuit and rf circuit description will describe only one
channel because the other channel is identical for both. The local
oscillator (LO) section is common for both channels and will be
described separately.

Audio Section

AUDIO A
AUDIO B

NOISE A
NOISE B

MARCAD

DIVERSITY

CIRCUIT

LOW BATTERY

DETECTOR

4-POLE

LP

FILTER

TONE KEY

DETECTOR

COMPANDER DE-EMPHASIS

TTL

CIRCUIT

MUTING
CIRCUIT

SQUELCH

TTL OUT

TONE

CONTROL

TO AUDIO LEVEL BAR DISPLAY

OUTPUT

STAGE

XLR OUT
1/4” OUT

Figure 2. UC4 Audio Section Block Diagram

The audio for each channel comes from the appropriate channel
detector output of the rf section. Each channel’s audio then enters its
own adjustable gain stage.

This adjustable gain stage is used to match the audio levels coming
from each rf channel, as well as to set the correct level necessary for the
compander.

From the gain stages, each channel enters an analog switch. Noise
outputs also come from each channel detector outputs. Each noise
output enters a bandpass noise filter that measures the 50 kHz noise
present in the audio signal. The noise level is proportional to the signal­to-noise ratio of the channel.

Parts Designations

MARCAD diversity system, a rectified version of the noise is

In the
sent to a bank of comparators. A version of the channel noise that is 6
dB less also enters the comparators.

The noise from one channel is compared to the noise from the other
to make sure they are within 6 dB of each other. If the noise levels are
within 6 dB of each other, the comparators send a logic high signal to the
control of each channel’s analog switch, allowing the audio to pass
through.

2

25C1045 (TK)

Shure UC4 Diversity Receiver

If the noise levels are not within 6 dB of each other, the channel with
a noise voltage 6 dB greater than the other channel is not allowed to
pass through the analog switch; that is, the comparator puts a logic
low signal on the control line for the analog switch.

Each channel’s noise is also compared to an adjustable squelch
level; a dc level. If either noise voltage is greater than the squelch
threshold, it is shut off.

The outputs from the analog switches are connected together at the
audio combining stage, a unity gain buffer stage where the audio from
Channel A is combined with the audio from Channel B.

The output from this stage splits into three paths. The first path goes
to a high Q tone key detection circuit. This is a crystal filter in which the
level of tone key is converted to dc and compared against a fixed dc volt­age.

The second path enters a low Q bandpass filter centered around 32
kHz. This filter is for low battery detection in the receiver. The lower Q
allows for small frequency variation of tone key from various transmitters,
without the large amplitude variations that the crystal filter would have.
The filtered signal is then rectified and averaged. The dc that is obtained
from this is amplified, triggering a comparator for the low battery LED
display.

The third path is into the compander via a 24 kHz low-pass filter with
a 32 kHz notch. The audio is expanded and de-emphasized here. The
compander output then goes off the board to a high and low frequency
equalization circuit.

A user-adjustable gain stage follows. The signal is then brought
back to the main audio board, where it enters a balanced and unbal­anced output stage. The balanced output can be set for either mic or
line level, where the mic level is 30 dB down from the line level.

For the audio level meter, audio is tapped off from the 24 kHz filter’s
output and goes through a full wave precision rectifier and averaging cir­cuit. This dc signal then enters a dc amplifier stage used to adjust levels
for the LEDs.

The output from this stage drives the audio level meter on the front
panel board. For the rf level meters, a dc voltage from the detector chip
for the received signal strength indicator (RSSI) drives the bargraph IC
on the front board.

Parts Designations325C1045 (TK)

Shure UC4 Diversity Receiver

Rf Section

DIELECTRIC

FILTER

LNA

DIELECTRIC

FILTER

FIRST
MIXER

RF CHANNEL A

FIRST IF

FILTER

SECOND

MIXER

SECOND IF

FILTER

FM

DETECTOR

AUDIO A
NOISE A
RSSI A

FROM

MICROPROCESSOR

DIELECTRIC

FILTER

FIRST LO

SYNTHESIZER

LNA

SECOND LO

VCO

DIELECTRIC

FILTER

LOW PASS

FILTER

FIRST
MIXER

FIRST IF

FILTER

RF CHANNEL B

SECOND

MIXER

SECOND IF

FILTER

FM

DETECTOR

AUDIO B
NOISE B

RSSI B

Figure 3. UC4 Rf Section Block Diagram

The rf input signal is provided from the antenna ports to the receiver
by BNC connectors. Antenna port A is connected to J101 (channel A),
and antenna port B is connected to J201 (channel B).

The rf circuit description will describe only one channel because the
other rf channel is identical. The local oscillator (LO) section is common
for both channels and will be described separately.

Rf Channel

The rf signal is pre-selected to the 782 – 806 MHz frequency range
with two dielectric filters. The first dielectric filter is located between the
antenna port and the low noise amplifier (
located between the

LNA block and mixer input.

LNA). The second filter is

Parts Designations

The

LNA and the first mixer consist of a dual gate GaAs MOSFET.

The first conversion gives the first intermediate frequency (IF) signal at
50 MHz.

The first IF signal is amplified with

MMIC, band limited with a SAW

filter, and then down-converted to the second intermediate frequency (IF)
at 10.7 MHz with a second down-converter.

The second

IF signal is filtered by 10.7 MHz ceramic filters and

amplified by a 10.7 MHz pre-amp (Q105).

The 10.7 MHz signal goes to the second IF gain block with a
detector. The audio output is buffered and then processed as stated in
the audio section circuit description. The noise output is amplified to pro­vide signal for the noise squelch circuitry. The Received Signal Strength
Indication (RSSI) output of the detector drives the LEDs that are located
on the receiver’s front panel.

4

25C1045 (TK)

Local Oscillator (LO)

The first local oscillator (LO) is common for channel A and channel B

rf strips. The LO is a phase-locked loop (PLL) system.

The PLL consists of a prescaler/synthesizer, voltage-controlled
oscillator (VCO), a loop filter, a VCO, an rf power divider, and a bandpass
filter. The PLL limits the LO signal before injection to the first down con­verter, Q102 and Q202.

The prescaler receives the rf signal from the VCO via the coupling
capacitor, C333. The output from the phase detector is connected to an
external loop filter that controls the tuning voltage input to the VCO. The
prescaler/synthesizer IC is a serial-programmable input IC. It receives
the frequency programming data from the microprocessor, which is set
by the user, as described in the digital circuit description.

Digital and Display Section

Shure UC4 Diversity Receiver

ROTARY
SWITCH

ROTARY
SWITCH

(FREQ)

AUDIO

RSSI A

RSSI B

(CH)

EEPROM

MICROPROCESSOR

LED DRIVER

LED DRIVER

LED DRIVER

SHIFT

REGISTER

TO SYNTHESIZER

7 LED BAR

5 LED BAR

5 LED BAR

SHIFT

REGISTER

Figure 4. UC4 Digital and Display Section Block Diagram

Parts Designations525C1045 (TK)

Shure UC4 Diversity Receiver

Microcontroller

The microcontroller section consists of a U703 microcontroller and a

two digit, seven segment, LED display.

The LED display indicates frequency in terms of compatible channels
in a group. The LED display on the left indicates the current group. The
LED display on the right indicates the channel. Each LED is capable of
displaying digits 0 – 9. However, the channel LED also displays alpha
letters A – F.

Serial shift registers, U705 and U705, latch the current LED display.
A serial Load Enable (LE) signal of the display driver section is also
shared with the rf interface section.

A 4.0 MHz oscillator, Y701, provides the operating frequency to the
microcontroller. The oscillator circuit includes capacitors C702, C703,
with the crystal oscillator, Y701.

Resistor R704, C704, and U702 make up the reset circuit. The
microcontroller is reset if the supply voltage to it drops below 4.3 Vdc.

Memory

The memory section consists of U701, a non-volatile Electrically
Erasable and Programmable Read Only Memory (EEPROM). The

EEPROM stores the mapping of the compatible groups and channels

with respect to rotary switch positions.

The microcontroller serially communicates with the memory via data
and clock lines to read the frequency corresponding to the group and
channel position. Write to the memory only occurs during factory pro­gramming. During normal usage, this memory is used as a look-up table
only.

Resistors R702 and R703 allow in-circuit programming of the U701

EEPROM by letting data and clock lines be driven independently of the

microcontroller port pin states. R701 is the pull-up resistor for the data
line.

Audio / Rf Interface

The OUT ENAB signal gives the microcontroller the ability to mute
the audio during turn on and off, and frequency changes.

The microcontroller sets the phase-lock loop (PLL) to the required
signal using the DATA signal (U703, pin 12) to send the frequency initiali-
zation and set-up data. This data is clocked into the PLL by the micro­controller through the
Enable (
into a PLL’s internal registers to initialize and set the frequency.

LE) signal (U703, pin 10). The LE signal loads the clocked data

CLOCK signal (U703, pin 12) and the Load

Parts Designations

6

25C1045 (TK)

Shure UC4 Diversity Receiver

Rotary Switches for Frequency Selection

A 10-position group switch (S701) and a 16-position channel switch
(S702) select the receiver frequency. The current position of these
switches is displayed on the 7-segment LED display. Both rotary
switches share the same U703 microcontroller port pins (3 through 6)
for a multiplexed switch read operation.

The individual switches are selected by pins 7 and 8 of the U703
microcontroller. Resistors R705 through R708 are the pull-ups for switch
position read. Dual diodes D701 through D704 isolate the switches dur­ing multiplexed read operation.

The multiplexed scheme to read switches does not allow switch
change detection based on interrupts. Also, the switches cannot be
constantly scanned to determine changes because the scanning fre­quency is in audio range, which makes it hard to filter out.

In a steady state, the switch common pins are inputs to pins 7 and 8
of the U703 microcontroller, while pins 3 through 6 of the microcontroller
are outputs In this state, pins 4, 5, and 6 are held low which pin 3 is held
high. This forces the logic high level on switch common pins if the
switches are set on odd positions. For even position settings, the contact
on pin 1 is open from the switch common pin, and the internal pull-down
resistors force logic low to the U703 microcontroller, pins 7 and 8.

Any switch change is done by state toggle from odd to even, or vice
versa. Only this change is detected and followed by a multiplexed switch
read. In this case, U703 microcontroller pins 7 and 8 selectively become
grounded outputs to read the selected switch’s state on pins 3 through 6.

A multiplexed switch read is preceded by an audio mute. The
receiver audio is muted to allow a quiet change to another frequency.

Power Switch Interface

When a receiver is switched off, the MT signal goes to logic low on
U703, pin 19. This interrupts the microcontroller to immediately mute the
audio so that the receiver turns off without any audio pop.

Parts Designations725C1045 (TK)

Shure UC4 Diversity Receiver

Notes

Parts Designations

This page intentionally left blank.

8

25C1045 (TK)

Shure UC4 Diversity Receiver

Functional Test

Verify operation and reported malfunction, referring to the product
User’s Guide for a description of the unit as well as information on its
operation, troubleshooting, and technical data.

Disassembly and Assembly

! CAUTION !

Observe precautions when handling this static-sensitive device.

Disassembly

Top Cover Removal

1. Remove two screws and washers each from the top, left, and
right sides of the receiver (6 screws).

2. Slide the top cover off of the receiver to expose the circuit
boards.

Front Panel Removal

1. Pull up on the top two tabs to partially release the front panel
from the chassis.

2. With a thin tool and the unit upside down, pry the front panel
away from the chassis at the two slots located on the bottom
of the front panel.

3. With the front panel disengaged from the chassis, carefully pull
the front panel away from the chassis.

Printed Circuit Board Removal

1. Pull the power knob off the power switch.

2. Disengage the front four standoffs from the chassis by pinching
the standoff ends, which will free the front circuit board.

3. Except for the dc power receptacle, remove all screws, nuts, and
washers from the back of the unit.

4. Unplug the connector between the dc power receptacle and the
circuit board.

5. Remove the remaining five screws that secure the circuit board.

6. Raise the front of the circuit board to clear the chassis; then
move the circuit board forward to free the rear components and
lift the circuit board out.

Parts Designations925C1045 (TK)

Shure UC4 Diversity Receiver

Reassembly

1. Insert the rear circuit board components into their mating chassis
holes, and lower the circuit board into its correct position.

2. Secure the circuit board with the previously removed screws.

3. Plug in the connector between the dc power receptacle and the
circuit board.

4. Replace all previously removed screws, nuts, and washers to the
back of the unit.

5. Snap the front circuit board with standoffs into the chassis front.

6. Push the power knob in to snap it back onto the power knob
shaft.

7. Line up the front panel, and push the front panel toward the
chassis. Make sure the ribbon cables are positioned to clear
light pipes.

8. Latch both bottom and top tabs to the front of the chassis.

9. Slide the top cover onto the chassis until the cover is tight
against the front panel.

10. Secure the top cover with the previously removed screws.

Parts Designations

10

25C1045 (TK)

Service Procedures

Reference Material

Refer to the Service Equipment Manual for standard test equipment.

Optional Modification

“F” Version (Or Later) Printed Circuit Boards (pcbs)

The UC4 can be modified to match different gain structures required
by different Shure UHF transmitters. There are two types of gain struc­ture in the UC4 in which one has more gain in the output stage and in
the audio LED circuitry. The UC4 can work with a U-series transmitter,
although the battery meter circuitry is not compatible between systems.
The modification in the table below alters the UC4 audio and LED gain.

To modify different UC receivers, check the label on the UC4 and
add or remove parts according to the following table:

Shure UC4 Diversity Receiver

PCB Label

LED R602 X X

LED R647 X
GAIN R651 X
GAIN R648 X
GAIN R649 X
GAIN D604 X

These modifications can only be done on

Measurement Reference

dBu is a measure of voltage, and dBm is a measure of power.

For example, the HP8903 should be labeled dBu instead of dBm
because it is a voltage measurement. These two terms are often used
interchangeably even though they have different meanings.

Audio levels in dBu are marked as dBm on the HP8903.

Place for Use

with UC

Reference

Designator

Transmitter

Group A

“F” version (or later) pcbs.

Place for Use

with UC

Transmitter

Group B,C,D,E

Place for Use
with U-series

Transmitters

dB Conversion Chart

0 dBV = 2.2 dBu

0 dBu = 0 dBm, assuming the load = 600 Ω

Parts Designations1125C1045 (TK)

Shure UC4 Diversity Receiver

Test Equipment

Most test equipment needed is described in the Shure Wireless

Service Equipment Manual. The following test equipment (or approved

equivalent) is also needed.

Equipment Type Model

Audio analyzer *Hewlett-Packard 8903B

Digital multimeter Fluke 87
Rf signal generator Hewlett-Packard 8656B
Frequency counter Hewlett-Packard 53181A
Spectrum analyzer Hewlett-Packard 8591

Shure UC transmitter Shure UC1 / UC2

*Audio levels in dBu are marked as dBm on the HP8903B.

Table 1

Test Equipment

Test Equipment Set-Up

The alignment procedure is sequential and does not change,

unless specified.

1. Use RG58 or any low loss, 50 Ω cables for all rf connections.

2. Keep the test cables as short as possible.

3. Include the insertion loss of the cables and connectors for all rf
measurements.

4. Dc voltages may be present at rf test points. As a precaution,
use dc blocks to protect the test equipment

Parts Designations

12

25C1045 (TK)

Test Set-Up

Shure UC4 Diversity Receiver

TPRF2

J201

FL201

FL205 FL105

FL212

FL216

FL215

LABEL

C319 C318

TPRF1

U303

Y301

U301

C323

C3301

Y302

C316

C336

C330

FL101

FL115

J101

FL112

TPRF3

FL116

TP36

Y501

R225

J501

C605

U601

FL217

FL117

U405

C601

U406

C239

C610

C602

C502

C627

TPB6

D402

U402

U201

J602

FL218

C611

TPB5

S601

C622 C624 C623

U603

U403

C418

U404

C404

J402

R406

FL219

C236

U605

TPA6

+ 5 V**

R125

R405

C621

C618

C603

U401

TPA5

C606

C403

C401

J601

C513

C147

C607

U602

+ 10 V**

U501

J901

D901

TK ON TK OFF

S501

C504

C509

C903

J401

D902

*

C904

+

U901

C906

U902

C905

* F version and earlier
** G version and later

*

C908

C139

U701

+

U703

Y701

U101

FL118

FL119

Figure 5. UC4 Major Test Component Locations

1. Install the receiver antennas.

2. Set the receiver to any unused frequency in the area. Select a
television channel that is inactive in the area and then scan for a
frequency at which the yellow LEDs are not lit. Note this as the
operating frequency, “f 0”.

3. Remove the top cover from the receiver.

C136

S901

Parts Designations1325C1045 (TK)

Shure UC4 Diversity Receiver

Table 2 lists the group and channel switches, and the
operating frequencies for all the tests that follow.

Table 2

Group Carrier Frequencies

(in order by carrier frequency)

Group

Group

Code

Group

Switch

(S302)

Channel

Switch

(S301)

Operating

Frequency

“f 0” (MHz)

UA A 8 8 798.125

UB G 8 8 707.625
MB B 8 8 808.375
MC F 8 8 779.500
MD B 8 8 808.500

JB D 3 3 807.375

KK E 8 8 847.500

Parts Designations

14

25C1045 (TK)

Alignment

Shure UC4 Diversity Receiver

1. Connect the UC4 receiver as shown below in Figure 6.

2. Connect the rf signal generator EXT modulation input to the
audio analyzer output.

3. Set the rf signal generator for external FM.

4. Set the audio analyzer’s output impedance to 50 ohms and
adjust audio signal amplitude in small increments until both the
HI EXT and LO EXT lights on the rf signal generator turn off.
This should occur at an amplitude of about 1.43 V.

5. Engage the audio analyzer’s 400 Hz high-pass and
30 kHz low-pass filters.

6. Set the rf signal generator deviation as given in table below.

7. Turn the volume potentiometer full clockwise (maximum).

8. Set the Group select switch (red knob) according to Table 2.

9. Set the Channel select switch (black knob) according to Table 2.

10. Set the low EQ full clockwise and set high EQ to mid-range.

11. Set the squelch to mid-range.

12. Set the MIC / LINE output switch to LINE.

13. Apply 15 Vdc to the power input of the receiver.

14. Turn the tone key switch to OFF.

UC4 RECEIVER (FRONT)

AB

SQUELCH

UC4 RECEIVER (BACK)

S501

(TONE KEY SWITCH)

TK ON TK OFF

AUDIO ANALYZER

RF SIGNAL GENERATOR

NOTE: DC VOLTAGES ARE PRESENT AT MOST
RF TEST POINTS. USE A DC BLOCK ON THE
RF SIGNAL GENERATOR TO PROTECT
TEST EQUIPMENT.

UC4 Receiver Audio Analyzer Rf Signal Generator

Output: Unbalanced Measurement: AC level EXT: FM

Gain: Maximum Output amplitude: 1.43 V INT: OFF

Squelch: Mid Frequency: 1 kHz Output amplitude: –108 dBm

Tone Key (S501): OFF Filters: Frequency: See Table 2

Group switch: See Table 2 Low-Pass (30 kHz): ON Deviation:

Channel switch: See Table 2 High-Pass (400 Hz): ON UA,UB,MB,MC,MD: 45 kHz

JB: 27.7 kHz

KK: 15 kHz

Figure 6. Alignment Test Set-Up

Parts Designations1525C1045 (TK)

Shure UC4 Diversity Receiver

Power Section

Checking the dc power will insure the correct dc biasing

is applied to the operating circuits.

C908

C904

AUDIO ANALYZER

+10 V

CHASSIS GND

UC4 Receiver

Power: ON (+15 Vdc) Connect + : F version and earlier:

Operating freq: See Table 2 Connect – : GND (chassis)

Audio Analyzer

C904 (+ side)
C908 (+ side)

G version and later:

+10 V
+5 V

Figure 7. UC4 Power Section Test Set-Up

1. For “F” and earlier pcb versions, measure +10.0 Vdc ± 0.2 Vdc at
the + side of C904 (10 V regulator out).

For “G” and later pcb versions, measure +10.0 Vdc ± 0.2 Vdc at
the test pad labeled + 10 V.

2. For “F” and earlier pcb versions, measure +5.0 Vdc ± 0.2 Vdc at
the + side of C908 (5 V regulator out).

For “G” and later pcb versions, measure +5.0 Vdc ± 0.2 Vdc at
the test pad labeled + 5 V.

Parts Designations

3. Measure the dc current drain from +15 V supply with the amp
meter. It should be less than 500 mV.

16

25C1045 (TK)

Local Oscillator

Shure UC4 Diversity Receiver

Performing the local oscillator alignment insures that the unit is fine­tuned to the operating frequency selected by the user. Adjusting C3301
controls the voltage-controlled oscillator (VCO) tuning voltage and the
synthesizer reference frequency.

FREQUENCY COUNTER

CH 2

CH 1

UC4 Receiver Frequency Counter

Power: ON (+15 Vdc) Operating freq: See Table 2

Operating freq: See Table 2 Connect CH 2: TPRF1 and GND

Channel switch: See Table 2

Group switch: See Table 2

TPRF1

C3301

Figure 8. UC4 Local Oscillator Test Set-Up

1. Use a BNC to rocket cable or a shield test lead to attach a spec­trum analyzer or frequency counter to TPRF1. (Remove sheild
top cover to access test point TPRF1.)

2. Adjust C3301 for (f 0 + 50 MHz) ± 5.0 kHz. If using a spectrum
analyzer, adjust the span so the frequency accuracy measure­ment is better than 5 kHz. (Refer to the instrument manual.)

Parts Designations1725C1045 (TK)

Shure UC4 Diversity Receiver

Rf Alignment

Channel A and B rf alignments are performed to increase the input

signal strength of the receiver and filter out noise.

Tuning FL115 and FL215 maximizes the rf sensitivity (input signal
strength). Tuning FL119 and FL219 minimizes the fm detector’s total
harmonic distortion (THD).

Rf Channel B

NOTE: DC VOLTAGES ARE PRESENT AT MOST

RF TEST POINTS. USE A DC BLOCK ON THE
RF SIGNAL GENERATOR TO PROTECT
TEST EQUIPMENT.

J101

TPRF3

AUDIO ANALYZER

RF SIGNAL GENERATOR

FL115

FL119

UC4 Receiver Audio Analyzer Rf Signal Generator

Output: Unbalanced Measurement:

Gain: Maximum Output amplitude: 1.43 V INT: OFF

Squelch: Mid Frequency: 1 kHz Output amplitude: –106 dBm

Tone Key (S501): OFF Filters: Frequency: See Table 2

Low-Pass (30 kHz): OFF

High-Pass (400 Hz): OFF

A weighting ON

SINAD/LOG-LIN
DISTN/RATIO

EXT: FM

Figure 9. UC4 Rf Alignment Channel B Test Set-Up

1. Connect the rf signal generator to J101 (TPRF3).

2. Set the rf signal generator amplitude output to –106 dBm.

3. Measure the audio at TPA5 and adjust FL115 for maximum
signal-to-noise (SINAD). The typical level is 12.0 dB; the lower
limit is 8.0 dB. Press the SINAD and LOG-LIN buttons for this
measurement in dB.

TPA5

Parts Designations

4. Turn off the A weighting filter and turn on the 30KHz and 400Hz
filters on the audio analyzer. Set the rf signal generator to –60
dBm and adjust FL119 for minimum total harmonic distortion
(THD) at TPA5 (≤ .7%). Press the DISTN button for this mea­surement in percentage.

5. Turn off the 30KHz and 400Hz filters and turn on the A weighting
filter. Set the rf signal generator back to –106 dBm and make
sure that the SINAD is still greater than 8.0 dB at TPA5. Press
the SINAD and LOG-LIN buttons for this measurement in dB.

18

25C1045 (TK)

Shure UC4 Diversity Receiver

Rf Channel A

J201

TPRF2

TPB5

FL219

FL215

AUDIO ANALYZER

RF SIGNAL GENERATOR

NOTE: DC VOLTAGES ARE PRESENT AT MOST
RF TEST POINTS. USE A DC BLOCK ON THE
RF SIGNAL GENERATOR TO PROTECT
TEST EQUIPMENT.

UC4 Receiver Audio Analyzer Rf Signal Generator

Output: Unbalanced Measurement: SINAD/LOG-LIN

DISTN/RATIO

Gain: Maximum Output amplitude: 1.43 V INT: OFF

Squelch: Mid Frequency: 1 kHz Output amplitude: –106 dBm

Tone Key (S501): OFF Filters: Frequency: See Table 2

Group switch: See Table 2 Low-Pass (30 kHz): ON Deviation:

Channel switch: See Table 2 High-Pass (400 Hz): ON UA,UB,MB,MC,MD: 45 kHz

A weighting: ON JB: 27.7 kHz

EXT: FM

KK: 15 kHz

Figure 10. UC4 Rf Alignment Channel A Test Set-Up

1. Connect the rf signal generator to J201 (TPRF2).

2. Set the rf signal generator amplitude output to –106 dBm.

3. Measure the audio at TPB5 and adjust FL215 for maximum
signal-to-noise (SINAD). The typical level is 12.0 dB; the lower
limit is 8.0 dB. Press the SINAD and LOG-LIN buttons for this
measurement in dB.

4. Turn off the A weighting filter and turn on the 30KHz and 400Hz
filters on the audio analyzer. Set the rf signal generator to –60
dBm and adjust FL219 for
minimum total harmonic distortion (THD) at TPB5 ( .7%).
Press the DISTN button for this measurement in percentage.

5. Turn off the 30KHz and 400Hz filters and turn on the A weighting
filter.Set the rf signal generator back to –106 dBm and make
sure that the SINAD is still greater than 8.0 dB at TPB5. Press
the SINAD and LOG-LIN buttons for this measurement in dB.

Parts Designations1925C1045 (TK)

Shure UC4 Diversity Receiver

Audio Alignment

Audio alignment insures that the compressor output in the transmitter
exactly matches the expander input in the receiver. If these do not
match, mistracking occurs and the audio signal between the transmitter
output and the receiver input does not have the same characteristics.

AUDIO ANALYZER

RF SIGNAL GENERATOR

J201

CHASSIS

GND

NOTE: DC VOLTAGES ARE PRESENT AT MOST
RF TEST POINTS. USE A DC BLOCK ON THE
RF SIGNAL GENERATOR TO PROTECT
TEST EQUIPMENT.

J101

TPB6

R225

R405

UC4 Receiver Audio Analyzer Rf Signal Generator

Output: Unbalanced Measurement: DC level,

dB or mV

Gain: Maximum Output amplitude: 1.43 V INT: OFF

Squelch: Mid Frequency: 50 kHz Output amplitude: –60 dBm

Tone Key (S501): OFF Filters: Frequency: See Table 2

Group switch: See Table 2 Low-Pass (30 kHz): ON Deviation:

Channel switch: See Table 2 High-Pass (400 Hz): ON UA,UB,MB,MC,MD: 45 kHz

EXT: FM

JB: 27.7 kHz

KK: 15 kHz

TPA6

R406

R125

Parts Designations

Figure 11. UC4 Audio Alignment Test Set-Up, part 1

1. Connect the audio analyzer to the external modulation input of
the rf signal generator.

2. Set the input measurement of the audio analyzer for AC level
and turn on the 30KHz and 400Hz filters.

3. Set the rf signal generator to –60 dBm and 45 kHz deviation
externally modulated with 50 kHz tone from the audio analyzer
output.

4. Apply an rf signal to the channel A antenna port (J201).

5. Put the positive (+) terminal of the dc voltmeter on TPB6, and
the negative (–) terminal to any rf chassis ground.

6. Adjust R225 for 6.00 Vdc ± 0.03 V for raw PCB 34A8580G and
earlier. Adjust R225 for 2.5 Vdc ±0.03 V for raw PCB 34A8580H
and later. Note this raw PCB number is printed on the rear of the
main PCB between the the antenna connectors.

20

25C1045 (TK)

NOTE: DC VOLTAGES ARE PRESENT
AT MOST RF TEST POINTS. USE A
DC BLOCK ON THE RF SIGNAL
GENERATOR TO PROTECT
TEST EQUIPMENT.

AUDIO ANALYZER

Shure UC4 Diversity Receiver

7. Apply the rf signal to the antenna port of channel B (J101).

8. Put the positive (+) terminal of the dc voltmeter on TPA6, and
the negative (–) terminal to any rf chassis ground.

9. Adjust R125 for 6.00 Vdc ± 0.03 V for raw PCB 34A8580G and
earlier. Adjust R125 for 2.5 Vdc ±0.03 V for raw PCB 34A8580H
and later. Note: this raw PCB number is printed on the rear of
the main PCB between the the antenna connectors.

RF SIGNAL GENERATOR

CHASSIS

GND

J201

R225

J101

TP36

TPB6

J602

TPA6

R406

R405

R125

UC4 Receiver Audio Analyzer Rf Signal Generator

Output: Unbalanced Measurement: AC level,

EXT: FM

dB or mV

Gain: Maximum Output amplitude: 1.43 V INT: OFF

Squelch: Mid Frequency: 1 kHz Output amplitude: –60 dBm

Tone Key (S501): OFF Filters: Frequency: See Table 2

Group switch: See Table 2 Low-Pass (30 kHz): ON

Channel switch: See Table 2 High-Pass (400 Hz): ON

Group Group Code

Tuning Deviation

(kHz)

TP36

(dBu ± 0.1 dB (mV) )

UA A 45 –6.8 (354)
UB G 45 –6.8 (354)

MB / MD B 45 –6.8 (354)

MC F 45 –6.8 (354)

JB D 27.7 –8.5 (292)

KK E 15 –15.3 (133)

Figure 12. UC4 Audio Alignment Test Set-Up, part 2

1. Set the audio analyzer frequency to 1 kHz and readjust the
amplitude to the reading given in the table above.

2. Put the positive (+) terminal of an RMS ac voltmeter in the audio
analyzer on TP36, and the negative (–) terminal to any rf chassis
ground.

3. Adjust R405 for the reading given in the table above.

4. Apply the rf signal back to channel A.

5. Adjust R406 until the ac voltmeter gives the reading in the table
above.

6. Set the UC4 balanced output to line level using the Mic/Line switch.

7. Measure the audio level at the balanced line–level output using
the following table:

Parts Designations2125C1045 (TK)

Shure UC4 Diversity Receiver

Group

Group

UA A 30 +6.7 dBu ± 2.0 dB +0.2 dBu ± 2.0 dB
UB G 30 +6.7 dBu ± 2.0 dB +0.2 dBu ± 2.0 dB

MB, MD B 10 –11.6 dBu ± 2.0 dB –18.1 dBu ± 2.0 dB

MC F 10 –11.6 dBu ± 2.0 dB –18.1 dBu ± 2.0 dB

JB D 10 +7.3 dBu ± 2.0 dB +0.8 dBu ± 2.0 dB

KK E 10 –9.7 dBu ± 2.0 dB –16.2 dBu ± 2.0 dB

Code

Deviation

(kHz)

1 kHz Audio

Balanced Output

1 kHz Audio

Unbalanced Output

8. Turn the tone key switch back ON.

Parts Designations

22

25C1045 (TK)

Product System Specifications

After tuning, the unit should meet the following specifications.

RF Carrier Frequency Range

774–862 MHz (782–806 MHz for U.S. models).

Working Range

152.4 m (500 ft), minimum, under typical conditions; 487.6 m

(1600 ft ) line of sight. Actual working range depends on rf signal
absorption, reflection, and interference

Audio Frequency Response

The audio output level at 100 Hz should be + 8.5 dB ± 2 dB
relative to the 1 kHz level.

The audio output level at 10 kHz should be – 18.5 dB ± 2 dB
relative to the 1 kHz level.

Modulation

±45 kHz deviation compressor-expander system with pre-and
de-emphasis (domestic models only; international models may vary).

Dynamic Range

>100 dB, A-weighted

Shure UC4 Diversity Receiver

Receiver Audio Output Level (Maximum)

+5 dBu typical, unbalanced output
+14 dBu typical, balanced output

Rf Sensitivity

–108 dBm at 12 dB SINAD

Image Rejection

90 dB typical

Spurious Rejection

70 dB typical
Ultimate Quieting (ref. 45 kHz deviation)
>100 dB, A-weighted

Audio Polarity

Positive pressure on microphone diaphragm (or positive voltage
applied to tip of WA302 phone plug) produces positive voltage on pin 2
with respect to pin 3 of low impedance output and the tip of the high
impedance

1

/4-inch output

System Distortion

(ref. ±45 kHz deviation, 1 kHz modulation)

0.4% Total Harmonic Distortion typical

Power Requirements

15 Vdc , 600 mA 50/60 Hz

Power consumption: 600 mA x 15 V, maximum

Transmitter battery life (typical): 8 hours
(with Duracell MN1604 9V alkaline battery)

Parts Designations2325C1045 (TK)

Shure UC4 Diversity Receiver

Bench Checks

Set-Up

Dc voltages are present at most rf test points. Use dc blocks to

protect the test equipment, if necessary.

Use RG58 or any other low loss 50 Ω cables for all rf connections.
Keep the test cables as short as possible. Include insertion loss of
cables and connectors when making rf measurements. The following is
an example of a bench check procedure for the UC4–UA. For all other
UC4 models substitue respective settings and measurement values
found in the alignment procedures.

786.250 MHz will be used as the operating frequency
(“f 0”) in the following procedures.

n Set the Group and Channel switches to 0.

No Power

No Audio

n Use the following settings:

Squelch: Center

Low Frequency Control: Maximum

High Frequency Control: Center

Volume: Maximum

n Set the MIC / LINE switch to LINE position.

n Set the tone key switch (S501) to OFF.

n Apply an rf signal of 786.250 MHz to J201 (CHA antenna jack) at

a level of –60 dBm. FM modulate the carrier 45 kHz with 1 kHz
audio.

n With the power supply connected, verify +15 V ± 1 V, as labeled

on the pcb. If this voltage is incorrect, try another power supply.

n If +15 V is correct, verify regulated +10 V and +5 V. If these are

incorrect, check the surrounding regulator circuitry for solder
shorts, solder deficiencies, backward diodes and capacitors.
If this is inconclusive, replace the corresponding regulator.

n Check for audio at the detector output, U201, pin 15. If there is

no audio there, the problem is in the rf section.

Parts Designations

n If audio is detected and the audio LEDs are lit, the problem is

occurring after the expander, U601. Follow the audio path from
this point until the point of discontinuity is found and replace the
corresponding part (s).

24

25C1045 (TK)

No Rf

Shure UC4 Diversity Receiver

n If audio is detected and the audio LEDs are NOT lit, there are

two possibilities. Either there is a break in the audio chain some­where between the detector (U201) and the expander (U601), or
the audio muting circuitry is engaged.

n Check for the first intermediate frequency (IF) signal at the output

of the SAW filter (FL112/FL212, pin 1). If there is no 50 MHz IF
signal, check to see if the first LO frequency at TPRF1 Is f 0 ±
50 MHz.

n If the first LO frequency at TPRF1 is NOT correct, there are three

possibilities: the voltage controlled oscillator (VCO) is bad;
synthesizer failure; or a microprocessor problem.

n If the first LO frequency at TPRF1 is correct, trace the front–end

amplifier (Q101/Q201), the first mixer (Q102/Q202), and the first
IF amplifier (U103/U203).

n If the 50 MHz first IF signal is present, check the 10.7 MHz

second IF at the input of the FM detector (U101/U201, pin 1).

n If there is no 10.7 MHz signal, check the second LO frequency at

TPA9/TPB9.

n If the second LO frequency is NOT present, check the crystal,

Y302, and the second LO circuitry.

n If the second LO frequency is correct, check the second mixer

(Q104/Q204) and the second IF amplifier (Q105/Q205).

n If there is a 10.7 MHz signal at the input of the FM detector,

check the FM detector IC (U101/U201) and the surrounding
parts. Replace them, if necessary.

Parts Designations2525C1045 (TK)

Shure UC4 Diversity Receiver

Replacement Parts and Drawings

Product Changes

Five variations of the Shure UC4 Diversity Receiver are available.

Table 3

UC4 Model Variations

(in order by frequency)

Country

Code

UA 782–806 MHz U.S.A. and Canada 90UA8793
UB 692–716 MHz U.S.A. 90UB8793

MB 800–830 MHz Europe 90MB8793
MC 774–782 MHz Netherlands 90MC8793
MD 800–820 MHz Scandanavia 90MD8793

JB 806–810 MHz Japan 90JB8793

KK 838–862 MHz United Kingdom 90KK8793

Parts Designations

The following comments apply to the parts list and the schematic:
Resistors: Unless otherwise noted, all resistors are surface-mount

1

with

/10 W rating and 1% tolerance.

Frequency

Range

Country

Designation

PCB

#

Parts Designations

Capacitors: Unless otherwise noted, non-polarized capacitors are
surface-mount
tolerance, and polarized capacitors are tantalum types.

NPO dielectric types with a 100 V capacity and a 5%

26

25C1045 (TK)

Shure UC4 Diversity Receiver

Table 4

Replacement Parts

Reference

Designation

A1 Cable/connector assembly, dc 90B8688
A2 Front panel assembly 90A8765

A3 Front panel and lens assembly 90A8810
MP1 Metal chassis 53A8506
MP3 Top Cover 53A8474
MP4 Front panel 65A8305
MP5 Gasket 36A8076
MP6 Knob, power 65A8302
MP7 Knob, volume 90A8764
MP8 Lens 65A8309
MP9 Light pipe 65A8306

MP10 RF cover shield 53A8467

MP11 Screws, hardware RPW626
MP12 Long rack mounting bracket 53A8481
MP13 Short rack mounting bracket 53A8459
MP14 Link bar (for mounting two UC4’s togather) 31A8138

Description

Shure Part

Number

Parts Designations2725C1045 (TK)

Shure UC4 Diversity Receiver

Table 5

PCB Assembly Parts

Reference

Designation

C333 Capacitor, 100 V, 8.2 pF 150DB828CA

C623,624,627 Capacitor, electrolytic, 47 x 63 V 86BE629

C3301 Capacitor, trim 152D02

D401,402,403,404,407,

408,409,410,501,502,

503,601,602,905

D405,406,811,812,

813,814

D504,817 LED, red 184A18

D603,701,702,703,704 Diode, dual switching, SMD, SOT-23, 1 V 184A07

D701,702,703,704 Diode, dual switching 184A07

D705 LED display 86A8442

D801,802,803,804,

805,806,807,808,809,

810,815,816

D901,902 Diode, power, rectifier, silicon, 1.1 V 184A20

DZ999 Surge suppressor 184A34

FL101,105,201,205 Filter, dielectric (See table 6) *140–07
FL102,107,202,302,303 Inductor, 15 nH SM 162N06
FL103,108,203,207,208 Inductor, 22 nH SM 162S06

FL104,204 Inductor, 8.2 nH SM 162W10
FL106,206 Inductor, 18 nH SM 162M06
FL109,209 Inductor, 470 nH SM 162V06

FL111,211 Inductor, 330 nH SM 162W06

FL112,212 Filter, saw 80A8195

FL113,213,305,306 Inductor, 220 nH SM 162C06

FL114,214 Inductor, 390 nH SM 162Y06
FL115,215 Coil, tunable 82A8005

FL116,117,118,216,

217,218

FL119,219 Coil, quadrature 82A8004

FL301 Filter, low pass (See table 7) *162–17

FL304 Inductor, 150 nH SM 162E06
J101,201 BNC jack, pcb mount, 50 Ω 95A8631
J401,402 Pin jack 95A8278

J501 Header, block, 3 pin 95A8579
J601 Connector, XLR 95A8598
J602 1/4”Jack, phone 95A8104
J901 Header 95A8272

Diode, dual switching 184A08

LED, green 184E18

LED, yellow 184D18

Filter, ceramic 86A8971

Description

Shure Part

Number

Parts Designations

28

25C1045 (TK)

Shure UC4 Diversity Receiver

Reference

Designation

L101,102,103,104,105,
201,202,203,204,205,301,
302,303,304,305,306,307,
308,501,502,601,602,603,

604,903

L152,252,352,353 Inductor 162N06

L153 Inductor 162L06
L154,254 Inductor 162W10
L156,256 Inductor 162M06

L157,253,257 Inductor 162S06

L159,259 Inductor 162V06
L163,263 Inductor 162W06
L164,264 Inductor 162Y06

LF901,902 Ferrite Bead 162A30

Q101,102,104,

201,202,204

Q103,203 Microwave Isolator 183A37

Q105,205,301,302 Transistor, NPN 183A17

Q303,304,305 Transistor, NPN 183A14
Q306,502,503,504 Transistor, NPN 183A24
Q603,604,605,606 Transistor, SMD, SOT-34, FET, TMOS 183A30

R125,225,405,406 Potentiometer, trim, 5 k 146D02

R4401,6602 Potentiometer, 100 k 46D8048

R6601 Potentiometer, 10 k 46A8048
R6603 Potentiometer, 10 k 46A8069

S501 Tone key Switch, slide 55A168
S601 Mic/Line Switch, slide, DPST 55A8061
S701 Group Switch 55B8121
S702 Channel Switch 55A8121

S901 Power Switch 55A8062
U101,201 Quad Detector, SMT, FM, IF 188A190
U103,203 IC amp, monolithic microwave 183A37

U301 VCO (See table 6) *187–04
U302,602 Regulator, 5 V 180 mA 188A115

U303 Serial Input PLL Freq Synthesizer 188A265
U401,402 IC Quad Op Amp 188A49
U403,501 IC Quad Comparator, ultra-low power 188A123

U404 IC quad switch / multiplexer 188A19

U405,406.603,604,605 IC amp, dual op 188A18

U601 IC Compandor, low voltage 188A126

U702 Under Voltage Reset 188C210

Ferrite Bead 162A12

Transistor, Dual Gate GaAs MESFET N 183A12

Shure Part

NumberDescription

Parts Designations2925C1045 (TK)

Shure UC4 Diversity Receiver

Reference

Designation

U704,705 8 Bit Serial in Parallel Out Shift Register 188A216

U801,802,803 Bargraph, Linear Display Driver 188A86

U804 Comparator, Dual Voltage SM 188A136
U901 Voltage Regulator, 10 V, 1 A 86A8918
U902 Voltage Regulator, IC 86B8930
Y301 Crystal, 24.0 MHz, XTAL 40A8016
Y302 Crystal, 60.7 MHz, XTAL 40A8013
Y501 Crystal, 32.768 kHz, XTAL 40A8010
Y701 Crystal, 4.0 MHz 140A005

*See Frequency Dependent Table, below.

Shure Part

NumberDescription

Table 6

Frequency Dependent Parts,

By Country Code

Reference

Designation

FL101,105,

201,205

U301 187A04 187A04 187C04 187A04 187B04 187D04

MC

774–782 MHzUA782–810 MHz

140E07 140A07 140D07 140C07 140F07 140G07

MB/MD

800–830 MHzJB806–810 MHzKK838–862 MHz

692–716 MHz

UB

Table 7

Frequency Dependent Parts,

By Printed Circuit Board Code

Reference

Designation

FL301 162A26 162A26 162B26 162A26 162B26 162A06

R602 not placed 145BJ000 not placed 145BJ000 not placed 145BJ000
R647 145BJ000 not placed 145BJ000 not placed 145BJ000 not placed
R651 145BJ000 not placed 145BJ000 not placed 145BJ000 not placed

F

774–782 MHzA782–810 MHzB800–830 MHzD806–810 MHzE838–862 MHz

Table 8

692–716 MHz

Programed Parts

Country

Code

UA 188UCR131UA
UB 188UCR131UB

MB 188UCR131MB
MC 188UCR131MC
MD 188UCR131MD

JB 188UCR131JB

KK 188UCR131KK

U701

EEPROM

U703

Microprocessor

188C238F

G

* Note: For replacement of U703 Microprocessor 188C238C you must replace the EEPROM U701 (188UCR131**)

Parts Designations

30

25C1045 (TK)

Shure UC4 Diversity UHF Receiver

UC4 Diversity UHF Receiver: Printed Circuit Board Legend