Shure u2 Service Manual

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

UHF Wireless System

SERVICE MANUAL CHANGE NOTICE

U2 HAND-HELD TRANSMITTER

Changes and corrections have been made to the Service Manual for the U2 UHF Hand-Held 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.

U2 SERVICE MANUAL REVISION HISTORY

Release Part Number Date Code

Original 25A1022 QE
Revision 1 25B1022 SA
Revision 2 25C1022 TD
Revision 3 25C1022 AG

CHANGES EFFECTIVE JULY 2, 2001

REMOVE

these pages from the

U2 Service Manual

22 22

INSERT

these Revised pages into the

U2 Service Manual

E2000 Shure Incorporated Printed in U.S.A.
25–1022–2 (AG)

Service Manual

U2 Hand-Held UHF Transmitter

General

Characteristics

The Shure Model U2 Hand-Held UHF Transmitter is a micro­processor controlled microphone-transmitter operating in the 774 to
862 MHz frequency range. This product is intended for use in high­end installed sound, rental, and concert sound applications. Different
frequency variations are available in various countries.

Controls and Indicators

1

2

3

5

4

5

ON

OFF

6

1. Grille

2. Programmable Display

3. Battery Fuel Gauge

4. Battery Cover

5. ON/OFF Switch

Figure 1. U2 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.

7

8

6. Antenna

7. Battery Compartment

8. MODE Button

9. SET Button

10. Audio Gain Control

9

10

GAIN

E1999, Shure Incorporated Printed in U.S.A.
25B1022 (AG)

Shure U2 Hand-Held UHF Transmitter

Circuit Description

Audio Section

Audio enters L248, an inductor used as an rf choke. The signal is
ac-coupled thr ough C201 into a 26 dB user-adjustable gain stage around
U201B. This gain stage is ex t ernally accessible to the user. C249, C250,
and C209 protect the preamplifier and bias circuits from rf interference.
R212 and R241 set up a half-supply bias, and R238 sets the ac input
impedance.

The amplif ied audio signal is then passed through a pre-emphasis
network before entering the com pr ess ion stage. R230, R202, and C203
set up two corners for the pre-emphasis network . The pre-emphasis
boosts the high frequencies befor e tr ansm ission.

This network feeds an NE575 compandor, U203, whic h utilizes an
external amplif ier U204B. The compandor perf orm s 2:1 logarithm ic com­pression of the audio signal. Additionally, the pre-emphasis network
plays a role in setting the hinge point (0 dB gain) of the compandor.

Transistors Q211 and Q207, along with crystal Y202, form the tone
key oscillator circuit. This circuit pr ov ides a stable, cont inuous 32.768
kHz sine wave. Transistor Q201 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 trans m itt ed signal; there ­fore, if the tone key or the transmit t er is turned off, the receiver will be
muted. The tone key squelch eliminates receiver noise associated with
loss of a carrier. Q206 acts as a switch for toggling the tone key ON/
OFF. It is cont rolled by the microprocessor. R286 allows for the tone key
amplitude level to be set.

The tone key circuit is powered via U210B. This is a dc am plif ier
used to multiply the 3V battery voltage up to 4.5 V (gain = 1.5). As the
battery volt age drops, the tone key supply voltage drops, decr easing
the amplitude of the oscillator. This is used to detect low battery in the
receiver. (This featur e was eliminat ed for JB models. )

The tone key signal, along with the processed audio signal, is then
fed to a summing amplifier U204A. R231 and R234 set up a half-supply
bias. R207, at the output of the summing amplifier, is used to help pre­vent spurious oscillations from the operational amplifier. Aft er passing
ac-coupling capacit or C213, the signal is fed to the rf module.

Rf Section

Processed audio enters an internal potentiometer R227, which is
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, R227 is adjusted for 5 kHz deviation with a –67.2 dBV, 1 kHz tone
injected into the mic input.) 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 to prevent interfer-

Circuit Description 25B1022 (AG)2

Shure U2 Hand-Held UHF Transmitter

ence from external rf fields. Regulated 5 Vdc power from the dc/dc con­verter ensures frequency stability even if the battery voltage drops.

The VCO is capable of tuning from 782 to 810 MHz with a 1 to 4 V
tuning voltage range. At the output of VCO U206, the rf signal splits into
two paths. The output of the VCO is coupled by C207 to the frequency
control pin of synthesizer U205.

The synthes iz er’s internal circuitry divides the signal as necess ar y to
the desired ref erenc e frequency of 125 kHz. The synthesizer contains a
quartz-controlled reference oscillat or cir cuit operating from a 4.0 MHz
crystal, Y203, that is adjusted by means of trim m er VC201.

The transmit t er out put fr equency is user-selectable in pre-set
increments. The size of the increment and the overall frequency range
depend on the model (KK, JB, MB , MC, MD, etc.) . Frequency select ion
is made via microproc ess or U104, which interfaces with the user through
the mode/selec t switches.

The output of the synthesizer is a series of pulses which are
integrated by a passive loop filter, R226, C231, R251, C237, R243, and
C257, to produce a cont rol voltage signal. The contr ol voltage signal is
then connected to the VCO through amplifier U210A which is used to
isolate the PLL filter from the audio modulat ion signals.

The VCO output is also coupled to an rf power resistive pad consist­ing of R255, R256, R257, R258, and an LC-matching network containing
C270, L202, and C217. The rf power amplifier, a dual gate MESFET,
Q203, is fixed tuned, and configured as a common source device.
Amplifier stability is obtained through resistive loading on input R237.
The output of Q203 contains a low-pass matching network, L207, and
LC-type low pass filter, LP201, providing 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 transmit t er is capable of delivering +10 dBm (10 mW ), maxi­mum to the 50 Ω helical antenna. During transm it ter power up and fre­quency select ion, the rf power is muted by bringing the base of Q209
high. This pr ov ides approximately 45 dB rf at t enuat ion until the PLL has
locked.

The transmitter rf is then unmuted by bringing the base of Q209 low.
During transmitt er power off conditions, volt age is first rem oved from the
VCO by bringing the base of Q208 high. In this way, the transmit ter
carrier signal is not allowed to drift off frequenc y during power on or
power off condit ions .

U2 Display Board

The Display Board consists of following circuitry blocks:

Microcontroller Section

The microcont roller section consist s of microcontr oller U104 and the
liquid crystal display (LCD). The microcontroller has an on-boar d LCD
driver. R104, R105, and R107 supply the microcontroller wit h the LCD
drive voltage for a 4- plex drive.

The LCD indicates the UHF frequency group and channel, and also
has a batt ery fuel gauge. A 4. 000 MHz oscillator, Y101, pr ovides the

Circuit Description25B1022 (AG) 3

Shure U2 Hand-Held UHF Transmitter

operating frequency to the microcont roller. The oscillat or cir cuit inc ludes
C102, C103, R106. R108. U105, R113, and C107 form the reset circuit .
U105 is the reset IC that resets U104 microcontroller if the 5 Vdc normal
operating voltage falls below 3. 5 Vdc. R112 is the pull-up res ist or for the
U104 programming voltage pin.

Memory Section

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

Battery Management Section

The battery management section consists of comparator U103. It is
used to measure the effective battery voltage, with reference to +5 Vdc,
by measuring the time taken to charge capacitor C105 to a reference
threshold of 0.1 VDE ± 0.01 Vdc. The battery is checked approximately
every five seconds. Comparator U103 alternately charges C105 with +5
Vdc reference and then the battery voltage (DPLUS signal). The micro­controller calculates the battery voltage by comparing the time difference
to charge C105, up to a reference threshold of 0.1 Vdc ± 0.01 Vdc, with
the +5 Vdc reference voltage and the battery voltage.

User Interface Section

The user interf ace section consists of power, MODE, and SET
switches. The LCD provides the user with feedback for all switch
operations.

Circuit Description 25B1022 (AG)4

Preliminary Tests

Test Component Locations

TOP

Shure U2 Hand-Held UHF Transmitter

BOTTOM

DIGIT AL DISPLAY BOARD

BOTTOM

R227 location for G and
later board versions.

TOP

R227 location for F and
earlier board versions.

RF-AUDIO BOARD

Figure 2. Test Component Locations

Preliminary Tests25B1022 (AG) 5

Shure U2 Hand-Held 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.

Use a U4 receiver for the following functional tests.

Test Set-Up

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

2. Insert two fresh AA batteries into the U2 battery nest.

3. Connect the audio analyzer to the microphone via the
microphone test head.

Rf Power

1. Attach a U4 antenna to the spectrum analyzer.

2. Turn the U2 on and hold it very close to the antenna. Move the
U2 up and down to maximize power on the spectrum analyzer.

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

Current Drain

1. Apply 3.0 Vdc to the battery terminals.

2. Connect the amp meter between the positive (+) battery lead
and the positive (+) battery terminal of the U2 transmitter.

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

Preliminary Tests 25B1022 (AG)6

Shure U2 Hand-Held UHF Transmitter

Frequency Response

Values between board versions may vary slightly; the following values
are typical values.

1. With the transmitter set to minimum gain, apply 100 mVrms
at 1 kHz to its input.

If you have a version with a 6 dB pad (JB model),
apply 200 mVrms at 1 kHz.

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 –8.5 dBu ± 2 dB.

5. Change the frequency to 100 Hz and verify that the measure­ment from the U4 unbalanced output is within ± 3.0 dB with
respect to the 1 kHz level.

6. Change the frequency to 10 kHz and verify that the measure­ment from the U4 unbalanced output is within ± 1.5 dB with
respect to the 1 kHz level.

Preliminary Tests25B1022 (AG) 7

Shure U2 Hand-Held UHF Transmitter

Notes

This page intentionally left blank.

Notes 25B1022 (AG)8

Shure U2 Hand-Held UHF Transmitter

Disassembly and Assembly

ATTENTION

Observe precautions when handling this static-sensitive device.

1. Refer to Figure 2 and remove the microphone head from the U2.

2. Remove the retaining ring from inside the top of the case, using
a pair of needle-nosed pliers.

3. Remove the screw located beneath the battery cup.

4. Slide the circuit board assembly out by pushing up on the antenna.

5. After complet ing all repairs, slide the circuit boar ds back into the
case; then reinstall the retaining ring, sc rew and microphone
head.

MICROPHONE

HEAD

RETAINING RING

PRINTED CIRCUIT BOARD ASSEMBLY

BATTERY NEST

RF GROUND

SCREW

CASE

CONDUCTIVE WASHER

ANTENNA

“O” RING

BATTERY

CUP

Figure 3. U2 Transmitter Disassembly and Assembly

Disassembly and Assembly25B1022 (AG) 9

Shure U2 Hand-Held UHF Transmitter

Notes

This page intentionally left blank.

Notes 25B1022 (AG)10

Service Procedures

Service Note

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 U2 Hand-Held UHF Transmitter

Service Procedures25B1022 (AG) 11

Shure U2 Hand-Held UHF Transmitter

Antenna Replacement

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 gask et 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 25B1022 (AG)12

Test Equipment

Measurement Reference

because it is a voltage measurement. These two terms are often used
interchangeably even though they have different meanings.

Shure U2 Hand-Held UHF Transmitter

dBu is a measure of voltage, and dBm is a measure of power.
For example, the HP8903 should be labeled dBu instead of dBm

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

dB Conversion Chart

0 dBV = 2.2 dBu

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

Table 1

Test Equipment

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 8590L

Shure U4 receiver Shure U4

SMC to BNC Adapter PT1838S

Audio Test Head PT1840

Test Head Brass Ring PT1838Y

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

Reference Material

Use the Shure UHF Wireless System User’s Guide for information
on Controls, Operation, Specifications, etc. Refer to the appropriate
User’s Guide or User ’s Guide Supplement for information on frequency
compatibility.

Service Procedures25B1022 (AG) 13

Shure U2 Hand-Held UHF Transmitter

Test Set-Up

1. Use a UA802 0. 61 m (2 ft) coaxial cable or an RG58 low-loss
50 Ω cable for all cable connections.

2. Include the inser t ion loss of the cables and connec t or s in rf
conductive power measurements.

3. Audio gain pot entiometer R208 does not need to be preset;
however, on JB models, GAIN should be set to maximum.

4. All rf measurements should be made through 50Ω SMC
connector J103.

5. Proper adapters should be used to connect the test equipment.

6. Apply 3.0 Vdc from a dc power supply to the respective U2
battery terminals.

7. Turn on the U2 by switching S101 to the ON position.

Output Power Confirmation

1. Using the spectrum analyzer, verify output power is at least
+8 dBm. JB models must have at least +8 dBm, but cannot
exceed +10 dBm.

2. Rf output power is not adjustable.

Service Procedures 25B1022 (AG)14

Rf Alignment

Shure U2 Hand-Held UHF Transmitter

FREQUENCY COUNTER

VC201

J103

U2 T ransmitter Frequency Counter

Power (S101): ON Connect CH2: J103

Gain: For JB models:

set to maximum

Figure 4. Rf Alignment Configuration

1. Verify that the transmitter is ON; switch S101 is set to the
ON position.

2. Connect the transmitter to the frequency counter via J103.

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

4. Adjust variable capacitor VC201 until the frequency counter
measurement matches the desired frequency, ±1 kHz, found in
the User’s Guide and User’s Guide Supplements.

Service Procedures25B1022 (AG) 15

Shure U2 Hand-Held UHF Transmitter

Audio Alignment

Deviation Reference Voltage

S201 (INSIDE U4)

U4 RECEIVER

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

BLOCK

Figure 5. Deviation Reference Voltage Set-Up

1. Turn the U2 transmitter OFF.

2. Remove the cover of the U4 receiver to expose the pcbs.

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

4. Set the rf signal generator to the same frequenc y as the U2.

5. Set the rf signal generator internal FM tone to 1 kHz modulation.

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

7. Set the rf signal generator amplitude to –50 dBm.

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

9. Set the output level of the U4 receiver to maximum.

10. Connect the voltmeter section of the audio analyzer to the
unbalanced output of the U4.

11. Verify that the voltage is 4.2 ± 0.5 dBu (1.26 ± 0.07 V) for UA, MA,
UB MB, MC, MD, and KK models , and –26.2 ± 0.5 dBu for II mod­els. This is the deviati o n ref eren ce vol tag e.

DC

AUDIO ANALYZER

12 . Disconnect the rf signal generator from the U4 and move switch

S201 on the U4 to the ON position.

13. Turn OFF the rf output power from the rf signal generator.

Service Procedures 25B1022 (AG)16

Shure U2 Hand-Held UHF Transmitter

Deviation Reference Voltage Adjustment

U201 U204

R227 for
G and later
board ver­sions

TEST HEAD

AUDIO ANALYZER

U4 RECEIVER

RETAINING

RING

R286

R227 for
F and earlier
board versions

20 dB

PAD

DC

BLOCK

U2 Transmitter Audio Analyzer

Power: +3 Vdc Measurement: AC level

Gain: Minimum; for JB models set to MAX Output: 1 kHz

Filters:

Low-Pass (30 kHz): ON

High-Pass (400 Hz): ON

Figure 6. Microphone Test Head Configuration

1. Slide the U2 circuit boards into the supplied test head retaining
ring assembly.

2. Attach the microphone test head to the test head retaining ring
assembly.

3. Connect the audio analyzer output to the microphone test head
input. Connect the shield probe to the audio analyzer’s input.

4. Turn the U2 transmitter ON.

5. Adjust the audio analyzer output for 1 kHz to achieve a level of

-5.0 dBu (436 mV) at pin 7 of U201 on the transmitter. For JB
models, adjust the audio analyzer for 1 kHz and -65 dBu at the
input of the test head.

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

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

8. Adjust R227 until the audio analyzer reads the deviation
reference voltage determined in the previous test, ±0.05 dB
(±0.2 dB for JB models).

9. Disconnect the audio analyzer from the U4 unbalanced output.

Service Procedures25B1022 (AG) 17

Shure U2 Hand-Held UHF Transmitter

Tone Key Level Adjustment

1. Use a dc power supply to apply 2.5 ± 0.01 Vdc to the
battery terminals.

2. No audio is applied to the audio input.

3. Do not use filters on the measuring instrument.

4. The tone key frequency will be approximately 32.768 kHz.

5. Adjust R286 so that a tone key level of -22.8 ±0.1 dBu (56 mV)
is measured at pin 1 of U204. For JB models, this level is
–24.7dBu ±0.1 dBu (45 mV).

Service Procedures 25B1022 (AG)18

Bench Checks

Dc Problems

n Verify the battery voltage is between 2 and 3.5 V.
n Check for proper Vcc and +5 V rf at Q208 (make all dc measure-

n Trace the dc back to the dc to dc converter.
n Check the power switch.
n Look for open coils, cracked parts, reversed polarity capacitors,

n Verify rf OFF signal changes from +5V at power up/power down

n Verify that battery voltage appears at U208, pin 1. Check for

n Verify Vds of Q204 is approximately –.025 V. Q204 should be

n Verify 5V dc/dc converter output at U208, pin 8. Check for open

Shure U2 Hand-Held UHF Transmitter

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

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

to 0V during normal operation. Trace the signal to the micropro­cessor. Q208 should be saturated during normal operation.

reversed polarity capacitors C239 and C247.

saturate d.

coil L205, reversed polarity or bad diodes D201 and D202, or
bad converter U208.

Rf Problems

n If the carrier is out of specification by less then 40 kHz and

cannot be corrected by adjusting VC201, check the values of
VC201, C224 and Y203. If these values are correct, replace
Y203. As a last resort, replace synthesizer U205.

n If the carrier frequency is not between 782 and 810 MHz, or is

unstable, the loop is unlocked. Check the solder connections at
the, head board, VCO, microprocessor (traces LE, D, and CK)
and synthesizer U205.

n Check for 4 MHz oscillation at pins 1 and 2 of U205. if not

replace the crystal Y203.

n Check the values and polarity of the loop filter: R226, C231,

R251, C237, R243, C257 U210, R227, and R270.

n Check the bias voltage of U205 pins 3 and 4 and U210, pin 8.
n As a last resort, replace synthesizer U205. The tuning voltage

of the VCO should be about 3 Vdc when the transmitter is pro­grammed for 800 MHz operation.

Bench Checks25B1022 (AG) 19

Shure U2 Hand-Held UHF Transmitter

Low Rf Output Power

n Check the polarity of the microwave isolator (rf IN is marked

with a dot).

n Check the polarity of the low-pass filter (rf IN is marked

with a dash).

n Check the polarity of Q203.
n Check for missing ground connections.
n Verify VCO output power.
n Check dc level at VCO Vcc pin.
n Isolate the VCO from the rest of the circuit by removing R255,

R256 and C207. The carrier frequency will no longer be locked,
but the output power from the VCO should be approximately
2 dBm into a 50Ω load.

n Check the VCO power output. If it is still low, the VCO is faulty.
n Verify power across C270. Isolate the rest of the circuit by

removing L202.

n Check the values of R255, R256, R257, R258, and C217.
n Verify dc bias of Q203. Verify rf Mute signal changes from +5V

at power up/down to 0V during normal operation. If Q209 is not
saturated during normal operation, the rf power at the antenna
port will be attenuated by approximately 45 dB.

n Isolate components, starting from the antenna port and working

back to the rf power amplifier.

n Check continuity from U207, pin 4, to the center conductor of

J201.

n Remove microwave isolator U207 and check the power output

of the low-pass filter at LP201, pin 4.

n Remove the low-pass filter and check the power output of the

amplifier at LP201, pin 1.

n Check the values of input and output matching networks Q203,

C270, L202, C217, L207, C225, and L210. Look for open coils.

n Check the values of bypass capacitors C259, C283, C242,

C218, and C276.

n Replace Q203.

Excessive Current Drain

n Isolate different sections of the circuit (rf, Audio, Digital, dc/dc

Converter). Look for capacitors with reversed polarity and im­proper resistor values.

Deviation Problems

n If R227 cannot be adjusted to obtain 45 kHz deviation, isolate the

problem in the Audio or rf section.

n Check the value of R227.

Bench Checks 25B1022 (AG)20

Shure U2 Hand-Held UHF Transmitter

Replacement Parts and Drawings

Model Variations

Different frequency versions of the U2 transmitter 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.

Table 2

U2 Model Variations

COUNTRY

CODE

UA 782–806 MHz U.S.A. and Canada 90UA8741K
UB 692–716 MHz U.S.A. 90UB8741K
MA 782–810 MHz Germany 90MA8741K

MB 800–830 MHz Europe 90MB8741K
MC 774–782 MHz Netherlands 90MC8741K
MD

JB 806–810 MHz Japan 90JB8741K

KK 838–862 MHz United Kingdom 90KK8741K

FREQUENCY

RANGE

To create an MD board, order the 90MB8741K PCB and install the MD EEPROM

COUNTRY

DESIGNATION

RF-AUDIO

PC BOARD NUMBER

Table 3

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 Drawings25B1022 (AG) 21

Shure U2 Hand-Held UHF Transmitter

Parts Designations

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

1

/10 W rating and 1% tolerance.

with

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.

Table 4

Replacement Parts

Reference

Designation

A1 SM58 dynamic cartridge assembly R158
A2 SM87A condenser cartridge assembly R165

A3 BETA 87A condenser cartridge assembly R166
MP1 Antenna, UA, MB, MC, MD, JB models 95A2029
MP2 Antenna, KK model 95B2029
MP3 Antenna, UB model 95C2029
MP4 Battery nest 65B1784
MP5 Battery nest screw 30K8136A
MP6 Compression spring (for battery nest) 44A311
MP8 Contact (gold mic contact) 53E2039
MP9 Handle (black) 32B827F

MP10 Headboard, pcb 34A1106B
MP11 Lens 65A1785
MP15 LCD (liquid crystal display) 95A8934
MP16 O–ring 66A307
MP17 Plug 36A8067
MP18 Sleeve (bottom portion of handle) 31B1721C
MP19 Retaining Clip Ring 30A1314
MP20 Washer (EMI) 36B8066
MP21 Screw, Round Head, #4 x 0.25 30C622B

Description

Shure Part

Number

Replacement Parts and Drawings 25B1022 (AG)22

Shure U2 Hand-Held UHF Transmitter

Table 5

Printed Circuit Board Replacement Parts: Side 1

Reference

Designation

J101,102 Socket strip (for LCD) 56G8068

P101 Battery contact (positive terminal) 56A8061
R208 Audio gain potentiometer, 0.1 W, 20%, 20 k 46B8049
S101 Power switch, toggle, DPDT 55A189

S102,103 Switch, pushbutton, SPST (for Mode/Set) 55A187

Y202 Tone key Crystal, 32.768 kHz 40A8010
Y203 Crystal, 4 MHz (for U205 reference) 40A8012

D201,202 Rectifier, Schottky, MBRS140 184A16

L204,205,206,

251,252

LP201 Filter, low pass, 33 MHz BW 162A17

Q201,205,211 Transistor, NPN SOT-23, MMBT5089L 183A38

Q204 Transistor, MOS FET, MDT3055EL 183A35

R227,286 Trimming pot, 1/4 W, 25%, 1 k 146B02

R230 Resistor, 1/10 W, 1–5, 249 145BF2490
U102 Diode, switching, 7000L 184A08
U103 Integrated Circuit, Comparator, LM339D 188A136

U201,204 Integrated Circuit, 33178 188A18

U203 Compander , integrated circuit, NE575 188A126
U205 PLL Frequency Synthesizer 188A134
U208 Integrated Circuit, 5V dc/dc converter, MAX751CSA 188A182

VC201 Capacitor, trim, 7 / 50 pF 152H02

Y101 Crystal, 4 MHz (for micro–controller reference) 140A005

Inductor 15%, 33 µH 162B16

Description

Non-SMT Components

SMT Components

Shure Part

Number

Replacement Parts and Drawings25B1022 (AG) 23

Shure U2 Hand-Held UHF Transmitter

Printed Circuit Board Replacement Parts: Side 2

Table 6

Reference

Designation

Non-SMT Components

J103 Antenna connector, SMC 95A8641

D203,204 Diode, dual 184A08

L202 Inductor 20%, 0.12 µH 162A10

L203,210,211,

248,249

Q101 Transistor, MOS FET, MDT3055EL 183A35
Q203 Transistor, Dual Gate Ga As MESFET, NE25139 183C12
Q207 Transistor, NPN SOT-23, MMBT5089L 183A38

Q206,208,209 Transistor, PNP SOT-23, MMBT5087 183A01

U105 Voltage detector 188B210
U210 Dual operational amplifier 188A118

Inductor 10%, 0.18 µH 162R10

Description

SMT Components

Shure Part

Number

Table 7

UA206 VCO Selection

Country Code UA206 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

UA207 Microwave Isolator Selection

UA207

Country Code

UA
MA

MB
MC
MD

JB
KK 187B07
UB 187C07

Replacement Parts and Drawings 25B1022 (AG)24

Table 8

Shure Part Number

187A07

Notes

Shure U2 Hand-Held UHF Transmitter

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Replacement Parts and Drawings25B1022 (AG) 25

Shure U2 Hand-Held UHF Transmitter

U2 Hand-Held Transmitter

Digital Display

Printed Circuit Board Legend

“F” and Earlier Board Versions

Replacement Parts and Drawings 25B1022 (AG)26

Shure U2 Hand-Held UHF Transmitter

U2 Hand-Held Transmitter

Digital Display

Printed Circuit Board Legend

“G” and Later Board Versions

Replacement Parts and Drawings25B1022 (AG) 27

Shure U2 Hand-Held UHF Transmitter

U2 Hand-Held Transmitter

Rf-Audio Printed Circuit Board

Legend

“F” and Earlier Board Versions

Replacement Parts and Drawings 25B1022 (AG)28

Shure U2 Hand-Held UHF Transmitter

U2 Hand-Held Transmitter

Rf-Audio Printed Circuit

Board Legend

“G” and Later Board Versions

Replacement Parts and Drawings25B1022 (AG) 29

Shure U2 Hand-Held UHF Transmitter

U2 Hand-Held Transmitter

Microphone Head Board

Replacement Parts and Drawings 25B1022 (AG)30

Notes

Shure U2 Hand-Held UHF Transmitter

This page intentionally left blank.

Notes25B1022 (AG) 31