Shure u1 Service Manual

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

UHF Wireless System

SERVICE MANUAL CHANGE NOTICE

U1/U1L UHF BODY-PACK TRANSMITTER

Changes and corrections have been made to the Service Manual for the U1/U1L UHF Body-Pack Trans­mitter. These changes will make it easier to repair the transmitters. 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.

U1/U1L SERVICE MANUAL REVISION HISTORY

Release Part Number Date Code

Original 25A1021 QE
Revision 1 25B1021 SA
Revision 2 25C1021 TD
Revision 3 25C1021 AG
Revision 4 25C1021 BF
Revision 5 25C1021 BG

CHANGES EFFECTIVE JULY 12, 2002

REMOVE

these pages from the

U1/U1L Service Manual

21 to 25 21 to 25

INSERT

these Revised pages into the

U1/U1L Service Manual

E2000, Shure Incorporated Printed in U.S.A.
25–1021–2 (BG)

U1/U1L Body-Pack

General

Characteristics

The Shure U1/U1L Body-Pack UHF Transmitter is a microprocessor­controlled body-pack transmitter operating in the UHF frequency range.
This product is intended for use in high-end installed sound, rental, and
concert sound applications. Different frequency variations are available.

Controls and Indicators

1

2

Service Manual

UHF Transmitter

NOTE: All models shipped after February 1999
have a soldered attached antenna to replace the

541

3

screw-on removable antenna. .

O

O

N

FF

10

11

7

6

12

13

8

9

1. Antenna

2. Programmable Display

3. Input Connector
(U1L uses LEMO connectors)

4. ON/OFF Switch

5. On/Off LED

6. Belt Clip

7. MODE Button

8. SET Button

9. Audio Gain Control

10. Battery Cover Release Tabs

11. Battery Compartment Cover

12. Battery Fuel Gauge

13. Battery Compartment

Figure 1. U1/UL Transmitter Controls and Indicators

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.

Licensing: Operation may require a user license. Frequency or power-output modifications
may violate this product’s approvals. Contact your country’s communications authorities.

E1999, Shure Incorporated Printed in U.S.A.
25B1021 (BG)

Shure U1/U1L Body-Pack UHF Transmitter

Circuit Description

Audio Section

Audio enters L201, an inductor that is used as an rf choke. The
signal enters a 6 dB pad made up of R203, R204, C204, and C206.
The signal is ac-coupled through C205 into a 40 dB (30 dB for JB
frequencies) user-adjustable gain stage around U201A.

This gain stage is externally accessible to the user. C201, C202,
and C207 protect the pre-amplifier and bias circuits from rf interference.
R205 and R207 set up a half-supply bias, and R206 sets the ac input
impedance.

The amplified audio signal is then passed through a pre-emphasis
network before entering the compression stage. R208, R211, and C211
set up two corners for the pre-emphasis network. The pre-emphasis
network boosts the high frequencies before transmission and helps set
the hinge point (0 dB gain) of the compandor. The network feeds NE575
compandor U203, which utilizes an external amplifier U202B. The com­pandor performs 2:1 logarithmic compression of the audio signal.

Transistors Q201 and Q202, along with crystal Y202, form the tone key
oscillator circuit, which provides a stable, continuous 32.768 kHz sine wave.
Transistor Q204 buffers the tone key signal before it is added to the audio
signal.

The tone key signal is used in the receiver to provide audio output only
when the tone key signal is present in the transmitted signal. Therefore, if
the tone key or the transmitter is turned off, the receiver will be muted.
Q203 acts as a switch for toggling the tone key on and off. It is controlled
via the microprocessor. R224 allows the tone key amplitude level to be set.

The tone key circuit is powered by U208B, which is a dc amplifier
that multiplies the 3 V battery voltage to 4.5 V (gain = 1.5). As the battery
voltage drops, the tone key supply voltage also drops, which decreases
oscillator amplitude. The tone key amplitude is used by the receiver
to indicate transmitter battery strength.

The tone key feature indicates battery level at the receiver. It is not
available on JB models.

The tone key signal, along with the processed audio signal, is fed to
summing amplifier U202A. Resistors R232 and R233 set up a half-supply
bias. Resistor R231, located at the output of the summing amplifier, pre­vents spurious oscillations from the operational amplifier. After passing
through ac-coupling capacitor C232, the signal is fed to the rf module.

Circuit Description

25C1021 (BG)2

Rf Section

Shure U1/U1L Body-Pack UHF Transmitter

Processed audio enters R243, an internal potentiometer adjusted for
45 kHz deviation (100% modulation) with a –7.2 dBV, 1 kHz tone, at the
output of the front audio stage (pin 1 of U201). On JB models, R243 is
adjusted for 5 kHz deviation with –63.2 dBV, 1 kHz tone, at the input to
the transmitter.

The audio is then fed to the tuning voltage pin of the voltage controlled
oscillator (VCO) and modulates the carrier directly. The use of a phase
locked-loop (PLL) frequency synthesized system eliminates the need for
multiplier stages, resulting in a much higher degree of spectral purity. The
VCO is shielded against interference from external rf fields. Regulated
+5 Vdc power from the dc-to-dc conv er ter ensures frequency stability,
even if the battery voltage changes.

At the output of VCO U205, the rf signal splits into two paths. The
output of the VCO is coupled by C244 to the frequency control pin of
synthesizer U204. The synthesizer’s internal circuitry divides the signal
as necessary to reach the desired reference frequency.

The synthesizer contains a quartz-controlled reference oscillator
circuit, including a 4.0 MHz crystal (Y201), that is adjusted by means of
trimmer capacitor C239.

The transmitter output frequency is user-selectable. Frequency
selection is made via microprocessor U103, which interfaces with the
user by means of the mode/select switches. The output of the synthesiz­er is a series of pulses that are integrated by a passive loop filter (R238,
C245, R240, C266, C267, R239, and C247) to produce a control voltage
signal. The control voltage signal is then connected to the VCO through
amplifier U210A, which is used to isolate the PLL filter from the audio
modulation signals.

The VCO output is also coupled to an rf power amplifier through a
resistive pad consisting of R254, R255, R256, R257, and an LC match­ing network containing C261, L209, and C248. The rf power amplifier,
dual gate MESFET Q208, is fixed-tuned and configured as a common
source device.

Amplifier stability is obtained through resistive loading on the input,
R247. The output of Q208 contains a low-pass matching network (L206)
and an LC-type low-pass filter (LP206), which provide a high degree of
spectral purity. The output of the low-pass filter feeds a microwave isola­tor that reduces the production of reverse third-order intermodulation
products.

The transmitter is capable of delivering a maximum of +10 dBm
(10 mW) to the 50 Ω antenna. During transmitter power-up and frequency
selection, rf power is muted by bringing the base of Q209 high. This pro­vides approximately 45 dB rf attenuation until the PLL has locked. The
transmitter rf is then unmuted by bringing the base of Q209 low. During
transmitter power off conditions, voltage is first removed from the VCO by
bringing the base of Q207 high. In this way, the transmitter carrier signal is
not allowed to drift off frequency during power on or power off conditions.

25C1021 (BG)

3

Circuit Description

Shure U1/U1L Body-Pack UHF Transmitter

Transmitter Display Board

The display board consists of the following circuitry blocks.

Microcontroller Section

The microcontroller section consists of microcontroller U103 and the
liquid crystal display (LCD). The microcontroller has an on-board liquid
crystal display (LCD) driver. R111, R113, and R114 supply the microcon­troller with the LCD drive voltage for a four-plex drive. The LCD indicates
the UHF frequency group and channel. The LCD also has a battery fuel
gauge. A 4.000 MHz oscillator, Y101, provides the operating frequency to
the microcontroller. The oscillator circuit includes C107, C108, R102, and
R103, which along with Y101, U106, R112, and C112, form the reset cir­cuit. U106 is the reset integrated circuit (IC) that resets the U103 micro­controller if the 5 V normal operating voltage falls below 3.5 V. R107 is
the pull-up resistor for the U103 programming voltage pin.

Memory Section

The memory section consists of U101, a non-volatile EEPRAM,
that stores current transmitter settings and the mapping of compatible
groups and channels.

Battery Management Section

The battery management section consists of comparator U102. It is
used to measure the effective battery voltage, with reference to +5 V, by
measuring the time used to charge a capacitor to a reference threshold
of 0.1 Vdc ± 0.01 Vdc. The battery is checked approximately every 5
seconds. Comparator U102 alternately charges C106 with +5 V refer­ence voltage, then the battery voltage (PLUS signal, test point I109).

User Interface Section

The user interface section consists of the Power, Mode, and Set
switches. The status of each switch function is indicated on the LCD.

Power Supply Section

The U105 dc-to-dc converter provides the transmitter with regulated
+5 V derived from two AA batteries. Power MOSFET Q101 provides
reverse battery protection. Q103, R1 18, R286, and C124 control the
soft start and reset of dc-to-dc converter following battery voltage drops.

Circuit Description

25C1021 (BG)4

Preliminary Tests

Test Component Locations

ABCD

Shure U1/U1L Body-Pack UHF Transmitter

*

*Shorted with a
0 Ω resistor on F
board versions
and later.

*On F
board
versions
and later.

Digital Display Board,

**

MC68H

Side 1

Digital Display Board,

Side 2

*

*On F
board
versions
and later.

Mic-Jack Board,

LEMO 4-Pin,

25C1021 (BG)

Rf-Audio Board,

Side 1

Figure 2. Test Component Locations

5

Rf-Audio Board,

Side 2

Mic-Jack Board,

TINI Q-G 4-Pin,

Preliminary Tests

Shure U1/U1L Body-Pack UHF Transmitter

Listening Test

Before completely disassembling the transmitter, operate it to deter­mine whether it is functioning normally and try to duplicate the reported
malfunction. Refer to the User Guide for operating instructions, trouble­shooting, and specifications.

Review any customer complaint or request, and focus the listening
test on any reported problem. The following, more extensive, functional
tests require partial disassembly.

Functional Tests

Refer to the Disassembly section to partially disassemble the
transmitter for the following functional tests.

Use dc blocks at all rf outputs to protect test equipment.

Test Setup

1. Use a U4 receiver for the following functional tests.

2. Dc voltages are present at most rf test points. Use dc blocks
to protect the test equipment, if necessary.

3. Connect the (+) power supply terminal through a milliammeter
to the (+) contact on the battery nest, and the (–) power supply
terminal to (–) the contact on the battery nest.

4. Connect a dc voltmeter across the power supply and set the
power supply for +3 Vdc..

5. Connect the audio generator to the mic-jack board either via the
TINI QG connector, or the LEMO connector to BNC cable,
depending on mic style.

Rf Power

1. Attach a U4 antenna to the spectrum analyzer.

2. Turn the U1 on and hold it very close to the antenna. Move the
U1 up and down to maximize power on the spectrum analyzer.

3. Verify that output power is greater than 3 dBm.

Preliminary Tests

Current Drain

1. Apply 3.0 Vdc to the battery terminals.

2. Verify that the current drain is less than 110 mA.

25C1021 (BG)6

Shure U1/U1L Body-Pack UHF Transmitter

Frequency Response

If the U1 has an attenuator switch on the back of the unit,
it should be set to –6 dB for the following tests (versions G or later).
Values between board versions may vary slightly; the following values
are typical values.

1. With the transmitter set to minimum gain, apply 200 mVrms
at 1 kHz to its input.

2. Connect the audio analyzer’s input to the unbalanced output of
the U4 receiver.

3. Make sure the receiver volume control is set to maximum.

4. With respect to the 1 kHz level, measure –8.22 dBu ± 2 dB.

5. Change the frequency to 100 Hz. Verify that the measurement
from the U4 unbalanced output is within ± 2 dB with respect to
the 1 kHz level.

6. Change the frequency to 10 kHz. Verify that the measurement
from the U4 unbalanced output is within ± 2 dB with respect to
the 1 kHz level.

25C1021 (BG)

7

Preliminary Tests

Shure U1/U1L Body-Pack UHF Transmitter

Notes

Notes

This page intentionally left blank.

25C1021 (BG)8

Shure U1/U1L Body-Pack UHF Transmitter

Disassembly and Assembly

ATTENTION

Observe precautions when handling this static-sensitive device.

Disassembly

NOTE: All models shipped after February 1999 have a soldered
attached antenna to replace the screw-on removable antenna.
Do not try to remove and replace the soldered attached antennas.

1. Open the battery compartment cover and remove the batteries.

2. Remove the belt clip.

3. Remove the two screws from the back of the case.

4. Lift the top half of the transmitter case away to expose
the printed circuit boards.

5. Remove the two screws securing the battery nest to the chassis.

6. Remove the rf ground screw, located next to the antenna.

7. Lift the printed circuit boards out of the case.

BATTERY NEST

BATTERY COMPARTMENT COVER

TOP COVER

RF SHIELDING GASKET

DIGITAL DISPLAY CIRCUIT BOARD

RF GROUND SCREW

RF-AUDIO CIRCUIT BOARD

ANTENNA

CONDUCTIVE WASHER
(SLIPS OVER ANTENNA)

NOTE: All models shipped after February 1999

BELT CLIP

have a soldered attached antenna to replace the
screw-on removable antenna. .

Figure 3. U1/U1L Hand-Held Transmitter Disassembly

25C1021 (BG)

9

Disassembly and Assembly

Shure U1/U1L Body-Pack UHF Transmitter

Reassembly

After completing all repairs, replace the antenna. Then place the
circuit boards back in the case, making sure the multi-pin connectors on
the boards mate. Reassemble the transmitter by performing the steps of
the disassembly procedure in reverse order.

Disassembly and Assembly

25C1021 (BG)10

Service Procedures

Service Notes

Units With Date Codes
Earlier Than August 1996

A small number of synthesizer ICs (U204) can experience start-up
problems with the 4 MHz crystal reference oscillator. The problem will
only occur for certain values of tuning capacitance.

The transmitter displays the correct group and channel information.
However , the carrier will have moved to its lowest possible frequency
(around 750 MHz). The tuning voltage of the VCO will read 0 Vdc.

Adjusting the crystal’s tuning capacitor to its lowest value should
cause the 4 MHz crystal oscillator to start up, and the carrier will lock
to the proper frequency.

The tuning capacitor can now be readjusted to center the carrier to
within ± 1000 kHz. However, once the unit is turned off, the problem may
return.

All units with August 1996 date codes or later have a 10 kΩ resistor
from pin 2 of the synthesizer to ground to insure that the internal
oscillator will start up for all values of tuning capacitance (C239). Safe
values for the resistor are from 16.8 to 33.2 kΩ.

Shure U1/U1L Body-Pack UHF Transmitter

Product Changes

Antenna Changes

antenna (70A8017) to replace screw-on removable antenna.

Attenuator Switch SW201

rf-audio printed circuit board. All products shipped after February 1997
(board versions “F” and later) should include this switch.

Inductor L104 Removal

discharge (ESD) performance. On products shipped after March 1997,
L104 was replaced with a jumper.

and the jumper was removed. Shure recommends that any product
shipped before March 1997 have L104 removed and replaced with a
jumper.

Comparator U102

All models shipped after February 1999 have a soldered attached

Attenuator switch SW201 has been added to the audio section of the

Inductor L104 has been removed for improved electrostatic

On “F” and later versions of the board, the circuit was redesigned

Comparator U102 has been changed to prevent an “88 88” display.

25C1021 (BG)

11

Service Procedures

Shure U1/U1L Body-Pack UHF Transmitter

Antenna Replacement

NOTE: All models shipped after February 1999 have
a soldered attached antenna to replace the screw-on
removable antenna. Do not try to remove and replace
the soldered attached antennas.

The top printed circuit board (pcb) is connected to the bottom pcb by
a multi-pin connector. Two wires also lead to the battery connector and a
three-wire flat cable that connects the pcbs to the microphone jack.

Handle the pcbs with care to avoid damaging these connections.

1. Open the battery compartment cover and remove the batteries.

2. Remove the belt clip.

3. Remove the two screws from the back of the case.

4. Lift the top half of the transmitter case away to expose the pcbs.

5. Remove the single screw visible next to the antenna connector.

6. Use the antenna to gently lift up both pcbs far enough so that the
antenna assembly clears the case, or remove the top pcb to gain
better access to the bottom pcb.

7. Remove the antenna by unscrewing it from the connector.
Make sure that the washer on the antenna clears the case.

8. Install the new antenna by screwing it onto the connector. If
necessary, replace the conductive rubber gasket at the base
of the antenna.

9. Return the pcbs to their original position.

10. Reinstall the single screw next to the antenna connector.

11. Perform these steps in reverse order to reassemble the unit.

Service Procedures

25C1021 (BG)12

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.

0 dBV = 2.2 dBu

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

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

Interconnect Cable Shure PT1843

BNC (Male) Cables (2) Shure PT1838A

DC Blocker Shure PT1838W

BNC (Female) to 1/4-inch Phone Plug Adapter Shure PT1838C

20 dB Attenuator Shure PT1838T

BNC to QG Cable Shure PT1825

BNC to LEMO Cable Shure PT1878
BNC (Female) to SMC (Female) Adapter Shure PT1838S
BNC (Female) to SMC (Female) Adapter Shure PT1838S

Test Cable, Japan Version Shure PT1838–AF

Adapter, Japan Version Shure PT1838–AJ

BNC (Male) to RG–174 Cable, unterminated Shure PT1824

Frequency counter Hewlett-Packard 53181A
Rf signal generator Hewlett-Packard 8656B
Spectrum analyzer Hewlett-Packard 8590L

Shure U4S receiver Shure U4S

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

Shure U1/U1L Body-Pack UHF Transmitter

dB Conversion Chart

Table 1

Test Equipment

25C1021 (BG)

Printed Circuit Board Interconnecting Cable

This cable is provided with the standard test equipment and is used
to connect U1 circuit boards that have been removed from the case for
servicing. It is made from two custom Shure printed circuit boards, a four­inch, 11-wire ribbon cable, and one male (Shure 170A07) and one
female (Shure 170A08) surface-mount connector. Note that the SMC
connectors face in opposite directions.

Female SMC connector

Figure 4. Printed Circuit Board Interconnecting Cable

13

Male SMC connector

(on back side)

Service Procedures

Shure U1/U1L Body-Pack UHF Transmitter

Rf Alignment

J3

U1 Transmitter Frequency Counter

Power (S103): ON Connect CH2: J3

Gain (R201): For JB models:

set to maximum

FREQUENCY COUNTER

CH 2

CH 1

Figure 5. Alignment Test Set–Up

Rf Alignment Set-Up

1. Proper adaptors should be used to connect the test equipment.

2. Use RG58 or other low-loss 50 Ω cables for all rf connections.

3. Include the insertion loss of the cables and connectors in
rf conductive power measurements.

4. Connect the rf–audio board to the digital board through
board interconnects J104 and J200.

5. On all models except JB, audio GAIN potentiometer R201 does
not need to be preset to any position. On JB models, R201
GAIN should be set to maximum.

6. All rf measurements should be made from the antenna output
connection, the 50Ω SMC connector on PCB versions “G” and
earlier or through the P1824 test cable on PCB versions “H” and
later. For JB models with SMT rf test connector, use PT1838–AF
with PT1838–AJ.

Rf Alignment

1. Slide the ON/OFF switch (S103) to the ON position.

Service Procedures

2. Connect the transmitter to the frequency counter via J3.

3. Determine the transmitter operating frequency by comparing the
Group and Channel information on the LCD to the tables in the
User Guide and User’s Guide Supplements.

4. Adjust variable capacitor C239 until the frequency counter mea­surement matches the desired operating frequency, ±1 kHz.

25C1021 (BG)14

Shure U1/U1L Body-Pack UHF Transmitter

Power Output Measurement

The output power measurement ensures that the output signal is
strong enough for sufficient range when the system is in use. The output
power measurement also verifies that the output power is not above the
specified maximum level, to ensure compliance with regulatory agencies’
standards.

SPECTRUM ANALYZER

U1 Transmitter Spectrum Analyzer

Power: ON Peak search: ON

Signal track: ON

Marker: ON

Figure 6. U1 Power Output Measurement Test Set-Up

1. Rf output power is not adjustable. Use RG58 or any other low
loss 50 Ω cables for all rf connections.

2. Include the insertion loss of the cables and connectors in
rf conductive power measurements.

3. Using the spectrum analyzer, verify output power is at least
+8 dBm. JB models must be at least +8 dBm and cannot exceed
+10 dBm.

25C1021 (BG)

15

Service Procedures

Shure U1/U1L Body-Pack UHF Transmitter

Audio Alignment

Deviation Reference Voltage

S201

TONE-KEY

SWITCH

U4 RECEIVER

DC BLOCK

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

RF SIGNAL GENERATOR

U4 Receiver Audio Analyzer Rf Signal Generator

Output: Unbalanced Measurement: AC level INT: FM

Gain: Maximum Filters: INT: 1 kHz

Squelch: Mid Low-Pass (30 kHz): ON Output Amplitude: –50 dBm

Tone Key (S201): OFF High-Pass (400 Hz): ON

AUDIO ANALYZER

Figure 7. Deviation Reference Voltage Test Set-Up, Using a U4 Receiver

1. The U1 transmitter should be turned OFF for this procedure.

2. Connect the rf signal generator to antenna A or B on a U4
receiver. Make sure the dc block is on the rf signal generator.

3. Set the rf signal generator to the same frequency as the
U1 transmitter.

4. Set rf signal generator modulation to 1 kHz and set the deviation
to 45 kHz for UA, UB, MA, MB, MC, and MD models, 40 kHz for
KK models, and 5 kHz for II models.

Service Procedures

5. Set the output amplitude of the rf signal generator to –50 dBm.

6. Turn the U4 receiver ON and set the tone key switch (S201)
inside the U4 receiver to the OFF position. This will disable the
receiver tone key function.

7. Connect the audio analyzer to the unbalanced output of the U4
receiver. The voltage should be 4.2 ±0.5 dBu (1.26 ± 0.07 V) for
UA, MA, MB, MC, MD, and KK models, and –26.2 ± 0.5 dBu for
II models.

Note the voltage obtained; it is the deviation reference voltage.

8. Disconnect the rf signal generator from the U4 receiver and
return the tone key switch (S201) to the ON position.

25C1021 (BG)16

Shure U1/U1L Body-Pack UHF Transmitter

Deviation Reference Voltage Adjustment

U4 RECEIVER

AUDIO ANALYZER

U1 Transmitter Audio Analyzer

Power: +3 Vdc Measurement: AC level

Gain: Minimum; for JB models,

set to MAX

Low-Pass (30 kHz): ON

High-Pass (400 Hz): ON

DC BLOCK

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

Output: 1 kHz

Filters:

20 dB PAD

Figure 8. Deviation Reference Voltage Adjustment Test Set-Up

1. The U1 transmitter should be turned ON for this procedure.

2. Turn the rf signal generator OFF for this procedure.

3. For G and later board versions, adjust the audio analyzer for 1
kHz to get a level of –5.0 dBu (436 mV) at pin 7 of U201.

4. For F or earlier board versions, adjust the audio analyzer for
1 kHz to get a level of –5.0 dBu (436 mV) at pin 1 of U201.

5. On JB models, adjust the audio analyzer for 1 kHz to –61.0 dBu
at the input connector.

6. Connect the transmitter rf output to a U4 antenna connector
through a dc block and a 20 dB pad.

7. Connect the U4 unbalanced output to the audio analyzer’s input.

8. Adjust R243 until the audio analyzer reads the deviation
reference voltage, measured in the last test, from the
unbalanced output of the U4 receiver, ±0.1 dB.

9. Turn OFF the 30 kHz low-pass filter and the 400 Hz high-pass
filter on the audio analyzer.

10. Disconnect the audio analyzer output from the U1 mic input.

25C1021 (BG)

17

Service Procedures

Shure U1/U1L Body-Pack UHF Transmitter

Tone Key Level Adjustment

AUDIO ANALYZER

U1 Transmitter Audio Analyzer

Power: +2.5 Vdc Measurement: AC level

Gain: Minimum; for JB models,

set to MAX

Output: None

Filters:

Low-Pass (30 kHz): OFF

High-Pass (400 Hz): OFF

Figure 9. Tone Key Level Adjustment Test Set-Up

1. Use a dc power supply to apply 2.5 ± 0.01 V to the battery
terminals, with no audio applied to the audio input.

2. Make sure no filters are used on the measuring instrument.

3. The tone key frequency will be approximately 32.768 kHz.
Adjust R224 so that the tone key level of –22.8 ± 0.1 dBu
(56 mV) is measured at U202, pin 1. For JB models, this level
should be –24.7 dBu ± 0.1 dBu (45 mV).

Service Procedures

25C1021 (BG)18

Bench Checks

Dc Problems

nMeasure the dc voltage at pin 1 of C104. This is the output of the

nMeasure the dc voltage at C113, pin 1, and C105, pin 1. It should

nVerify the battery voltage is between 2 V and 3.5 V.
nCheck for proper Vcc and +5 V rf at Q207 (make all dc measure-

nTrace the dc back to the dc to dc converter.
nCheck the power switch.
nLook for open coils, cracked parts, reversed polarity capacitors,

nVerify rf OFF signal changes from +5 V at power on/power off to

nVerify that the battery voltage appears at U105 pin 1.
nVerify that the Vds (drain to source voltage) of Q101 is approxi-

nVerify that the dc to dc converter output is 5 V at pin 8 on U105.

Shure U1/U1L Body-Pack UHF Transmitter

dc to dc converter. It should be 5V ±0.2 Vdc.

be 5V ± 0.2 V.

ments with respect to rf ground unless otherwise specified). If
incorrect voltage is present, check the values of the biasing
resistors.

solder shorts. If there is a short to ground from 5 V, isolate differ­ent parts of the circuit.

0 V during normal operation. Trace the signal to the microproces­sor. Q207 should be saturated during normal operation.

mately –0.025 V. Q101 should be saturated.

Rf Problems

25C1021 (BG)

nIf the carrier is out of specification by less than 40 kHz and

cannot be corrected by adjusting C239, check the values of
C239, C238, and Y201. If these values are correct, replace
Y201. As a last resort, replace synthesizer U204.

nIf the carrier frequency is not within the allocated UHF band-

width, or if it is unstable, the loop is unlocked. Check the solder
connections at the head board, VCO, microprocessor (traces LE,
D, and CK), and synthesizer U204.

nCheck for 4 MHz frequency at pins 1 and 2 of U204. If frequency

other than 4 MHz is detected, replace crystal Y201.

nCheck the loop filter: R238, C245, R240, C266, C267, R239,

C247 U208, R243, and R285.

nCheck U204, pins 3 and 4, and U208, pin 8.
nReplace synthesizer U204. The tuning voltage of the VCO

should be approximately 3 Vdc when the transmitter is pro­grammed for the center of the frequency range.

19

Bench Checks

Shure U1/U1L Body-Pack UHF Transmitter

Low Rf Output Power

nCheck the VCO power output. If the power output is still low, the

VCO is faulty.

nVerify power across C261. Isolate the rest of the circuit by

removing L209.

nCheck R254, R255, R256, R257, C261, L209, and C248.
nVerify the dc bias of Q208. Verify that the rf mute signal changes

from +5 V at power on/off to 0 V during normal operation. If Q209
is not saturated during normal operation, rf power at the antenna
will be attenuated by approximately 45 dB.

nIsolate components, starting from the antenna and working back

to the rf power amplifier.

nCheck continuity from U207, pin 1, to the center conductor of J3.
nRemove microwave isolator U207 and check the low-pass filter

power output at LP201, pin 4. It should be approximately 10 dBm.

nRemove the low-pass filter and check the power output of the

amplifier at LP206, pin 1.

nCheck the output matching network: Q208 C258, L206, and

C256.

nCheck the bypass capacitors: C254, C253, C252, and C5.
nReplace Q208.
nReinstall L209 and U207.
nCheck continuity between pins 1 and 4 of LP201.

Excessive Current Drain

nIsolate different sections of the circuit (rf, audio, digital,

dc to dc converter).

nApply +3 V to the battery terminals and measure the current

drain, using a dc milliammeter. It should be less than 110 mA.

Deviation Problems

nIf R243 cannot be adjusted to obtain 45 kHz deviation, isolate the

problem to either the audio or rf section.

nCheck R243.
nCheck the rf section by setting the transmitter frequency to

800 MHz and verifying that the tuning voltage of the VCO is
approximately 3 Vdc.

Bench Checks

25C1021 (BG)20

Shure U1/U1L Body-Pack UHF Transmitter

Replacement Parts and Drawings

Model Variations

Different frequency versions of the U1 and U1L transmitters are
currently available for use in various countries. Each version is identified
in the table below by country code, frequency range, and printed circuit
board version.

**Some frequency versions have been discontinued. For the new list
of frequency variations use the MK2 manual.

Table 2

U1/U1L Model Variations

COUNTRY

CODE

UA 782–806 MHz U.S.A. and Canada 90UA8739J 90UA8740M

MA 782–810 MHz Germany 90MA8739M

JB 806–810 MHz Japan *90JB8739J*

KK 838–862 MHz United Kingdom 90KK8739M –
MB 800–830 MHz Europe 90MB8739J –
MC 774–782 MHz Netherlands 90MC8739J –
MD
UB 692–716 MHz U.S.A. 90UB8739M 90UB8740M

FREQUENCY

RANGE

To create an MD board, order the 90MB8739J PCB’s and install the MD EEPROM .

**For PCB’s that are no longer available use the U1–MK2 manual for

replacements.

COUNTRY

DESIGNATION

U1

RF-AUDIO

PC BOARD NUMBER

(No Longer Available)

(No Longer Available)

PC BOARD NUMBER

(No Longer Available)

Parts Designations

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

with 1/10 W rating and 1% tolerance.

Capacitors: Unless otherwise noted, non-polarized capacitors are
surface-mount NPO dielectric types with a 100 V capacity and a 5%
tolerance, and polarized capacitors are tantalum types.

U1L

RF-AUDIO

*90MA8740M*

–

25C1021 (BG)

21

Replacement Parts and Drawings

Shure U1/U1L Body-Pack UHF Transmitter

U1/U1L Transmitter Replacement Parts

Table 3

Reference

Designation

A1 Belt clip assembly 90A4392
MP1 Antenna (removable); units shipped before 2/99 95A8731
MP2 Antenna (soldered); units shipped after 2/99 70A8019
MP3 Battery nest 95A8751
MP4 Battery nest screw 30K8136A
MP5 Bushing 66A308
MP6 Case back 32A8034A
MP7 Case door 32A8025A
MP8 Case top 32A8021A
MP9 Coil spring 44A8012

MP10 Conductive gasket 80C8198
MP11 Door spring 65A8243
MP12 Foam pad 36A675
MP13 Hinge pin 31A8142
MP14 Lens 65A8236
MP15 LCD (liquid crystal display) 95A8934
MP16 Nameplate 39B8227
MP17 Nameplate battery 39_8411
MP19 Retainer plate 53A8419
MP20 EMI Washer for use with 95A8731 antenna only 36B8066

Description

Shure Part

Number

Replacement Parts and Drawings

25C1021 (BG)22

Shure U1/U1L Body-Pack UHF Transmitter

Table 4

Printed Circuit Board Replacement Parts:

Side 1

Reference

Designation

MP21 Mic PCB Ribbon Cable 95A8622

J101,102 Socket strip 56G8069

R201 Potentiometer, 0.1 W, 20%, 100 k 46C8049

S101,102 Switch, pushbutton, SPST 55A187

Y202 Crystal, 32.768 kHz 40A8010

C239 Capacitor, trim, 7 / 50 pF 152H02

J200 Header, 11 Position 170A07

L101,102,103 Inductor 15%, 33 µH 162B16

L104 Resistor 1/8 W, 5%, 0 145AJ000

L201,203 Inductor 10%, 0.18 µH 162R10

L202 Ferrite bead 162A03
L206 Inductor 10%, 0.12 µH 162A10

LP206 Filter, low pass 162A17

Q101 Transistor, MOS FET, MDT3055EL 183A35
Q201 Transistor, NPN SOT-23, MMBT5089L 183A38
Q203 Transistor, PNP SOT-23, MMBT5087 183A01
R208 Resistor, 1/10 W, 1–5, 249 145BF2490

R224, 243 Trimming pot, 1/4 W, 25%, 1 k 146B02

U104 Diode, switching, 7000L 184A08

U201,202 Integrated Circuit, 33178 188A18

U203 Compander, integrated circuit, NE575 188A126
U204 PLL Frequency Synthesizer 188A134
Y101 Crystal, 4 MHz, for Microcontroller 140A005
Y201 Crystal, 4 MHz, for U204 140A09

Description

Non-SMT Components

SMT Components

Shure Part

Number

25C1021 (BG)

23

Replacement Parts and Drawings

Shure U1/U1L Body-Pack UHF Transmitter

Printed Circuit Board Replacement Parts:

Table 5

Side 2

Reference

Designation

Non-SMT Components

D102 LED, green 86C8419

J2 Receptacle, TINI QG, 4-pin, male: U1 ONLY 95A8413
J103 Receptacle, LEMO, OS: U1L ONLY 95A8601
S103 Switch, toggle, DPDT 55A189

D101,103 Rectifier, Schottky, MBRS140 184A16
D201,202 Diode, dual 184A08

J104 Receptacle 170A08

L200,205,208, 211 Inductor 10%, 0.18 µH 162R10

Q102 Transistor, MOS FET, MDT3055EL 183A35

Q103,202,204 Transistor, NPN SOT-23, MMBT5089L 183A38

Q207,209 Transistor, PNP SOT-23, MMBT5087 183A01

Q208 Transistor, Dual Gate Ga As MESFET, NE25139 183C12

SW201 Switch, 3-position 155A09

U102 Comparator 188A136
U105 Integrated Circuit, 5 V dc/dc converter,

MAX751CSA
U106 Voltage detector 188B210
U208 Dual operational amplifier 188A118

Description

SMT Components

Shure Part

Number

188A182

*Variations in part numbers correspond to country codes.

Table 6

U101 EPROM Table

Country Code Shure Part Number

UA 188T131UA
UB 188T131UB
MA 188T131MA

MB 188T131MB
MC 188T131MC
MD 188T131MD

JB 188T131JB

KK 188T131KK

Replacement Parts and Drawings

25C1021 (BG)24

Shure U1/U1L Body-Pack UHF Transmitter

Table 7

VCO Selection

Country Code UA205 VCO Range Shure Part Number

UA
MA
MC

JB

KK 837–863 MHz 187B10R
MB

MD

UB 692–716 MHz 187D10R

782–810 MHz 187A10R

800–830 MHz 187C10R

Table 8

Microwave Isolator Selection

UA207

Country Code

UA
MA
MB
MC
MD

JB

KK 187B07
UB 187C07

Shure Part Number

187A07

25C1021 (BG)

25

Replacement Parts and Drawings

Shure U1/U1L Body-Pack UHF Transmitter

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Replacement Parts and Drawings

25C1021 (BG)26

Shure U1/U1L Body-Pack UHF Transmitter

ABCD

SIDE 1

*Shorted with 0 Ω resistor.

*

MC68H

25C1021 (BG)

U1 / U1L Body-Pack Transmitter

Digital Display Board Legends and Foils

“E” and Earlier Board Versions

27

Replacement Parts and Drawings

SIDE 2

Shure U1/U1L Body-Pack UHF Transmitter

Replacement Parts and Drawings

U1 / U1L Body-Pack Transmitter

Digital Display Board Legends and Foils

“F” and Later Board Versions

25C1021 (BG)28

SIDE 1

Shure U1/U1L Body-Pack UHF Transmitter

25C1021 (BG)

U1/U1L Body-Pack Transmitter

RF–Audio Printed Circuit Board Legends

“E” and Earlier Board Versions

29

Replacement Parts and Drawings

SIDE 2

Shure U1/U1L Body-Pack UHF Transmitter

SIDE 1

U1/U1L Body-Pack Transmitter

Rf–Audio Printed Circuit Board Legends

“G” and Later Board Versions

Replacement Parts and Drawings

SIDE 2

25C1021 (BG)30

Shure U1/U1L Body-Pack UHF Transmitter

LEMO, 4-Pin TINI QG, 4-Pin

LEMO, 4-Pin TINI QG, 4-Pin

Mic-Jack Printed Circuit Board

Mic-Jack Printed Circuit Board

Legends and Foils

Legends and Foils

25C1021 (BG)

31

Replacement Parts and Drawings

Shure U1/U1L Body-Pack UHF Transmitter

Notes

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Replacement Parts and Drawings

25C1021 (BG)32