Characteristics
General
The Shure UC2 Hand-Held UHF Transmitter is a microprocessorcontrolled microphone transmitter, operating in the 774 to 862 MHz
frequency range. The UC2 hand-held transmitter is used in mid-level
installed sound, rental, and concert sound applications. Six frequency
range variations are available.
Controls and Connectors
Service Manual
UC2 Hand-Held
UHF Transmitter
1
2
1. Mic Cartridge Grille (87 shown)
2. Battery Fuel Gauge LEDs
3. Power ON/OFF Switch
4. Audio Gain Control
Figure 1. UC2 Controls and Connectors
Service Note:
performed by a Factory-Authorized Service Center or that the
product be returned directly to Shure Brothers Inc.
3
48
5
7
6
5. 9 V Battery
6. Battery Cup
7. Group Selection Rotary Switch
8. Channel Selection Rotary Switch
Shure recommends that all service procedures be
E1998, Shure Brothers Inc. Printed in U.S.A.
25A1044 (RI)
Shure UC2 Hand-Held UHF Transmitter
Circuit Description
LIMITER
CONTROL INPUT
FROM
BATT.
CONTROL
MIC
ON / OFF
SWITCH
FET
BYPASS
PWR.
HOLD
CIRCUIT
AUDIO IN
+5V
REG.
UNREG. PWR.
PWR. OFF DETECT
SYNTH.
MB15A02
RF POWER
+5v
32.768 kHz
PLL CONTROL
4 MHz
LIMITER
CONTROL OUTPUT
TONE KEY
CIRCUIT
TONE CONTROL
BATTERY
MGMT.
& FUEL
GAUGE
MCU
MC68HC705
GROUP CHANNEL
RF MUTE RF MUTE
TONE KEY
CALL ID
4 MHz
EEPROM
(MEM)
Σ
AUDIO
OUT
Audio Section
VCO
Figure 2. UC2 Hand-Held Transmitter Circuit Block Diagram
FCC-Approved
Audio enters L200, an inductor used as an rf choke. The signal is
ac coupled through capacitor C200 into a user adjustable gain stage.
Resistors R202 and R203 set up a half-supply bias, and R204 sets the
input impedance for the stage.
The back-to-back diodes, D201, are used to keep the op-amp from
snapping to the rail and reverse phasing when the maximum input voltage range is exceeded.
The 30 dB adjustable gain stage is built around U200A. The user
externally controls the gain of this stage. C206, C207, and C208 protect
Characteristics
2
25A1044 (RI)
Shure UC2 Hand-Held UHF Transmitter
the amplifier and bias circuits from rf interference. Due to its topology,
this stage is unique because it is non-inverting and allows for a gain less
than unity.
Audio then enters a buffer to the pre-emphasis network and the
compression stage. R213, R214, and C211 set up two corners for the
pre-emphasis network. The pre-emphasis boosts the high frequencies
before transmission.
This network feeds an NE575 compander, U202, that utilizes an
external amplifier, U201B. The compander performs a 2:1 logarithmic
compression of the audio signal. The pre-emphasis network also plays
a role in setting the hinge point (0 dB gain) of the compander.
From the compressor, the processed audio enters a low-pass filter,
U201D, and then a summing amplifier, U201C. The tone key (and for
J frequencies, the call ID signal) is added here to the processed audio
signal.
Transistors Q208 and Q209, with crystal Y200, form the tone key
oscillator circuit to provide a stable, continuous 32.768 kHz sine wave.
Transistor Q210 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 with the transmitted signal. If
the tone key or the transmitter is turned off, the receiver will be muted.
The tone key squelch eliminates receiver noise associated with
loss of a carrier. Q211 acts as a switch for toggling the tone key
UNMUTE
fed to a summing amplifier, U201C. R244, at the output of the summing
amplifier, helps prevent spurious oscillations from the op-amp. After
passing the ac coupling capacitor, C243, the signal is fed to the rf module
via the rf choke, L207.
D205; and various resistors. The meter works by comparing a divided
down version of the battery voltage (R250, R251) to two thresholds
(set by R252, R253, and R254), and lighting the appropriate LED.
(pcb), via switch S200. FET Q203 provides electrical reverse battery
protection by connecting the negative battery terminal to the pcb ground
only when the battery is connected with the correct polarity.
gives a clean, regulated 5 V supply to run the audio circuitry. The
regulator has appropriate bypass capacitors on its input and output.
Q201, Q202, Q212, Q213, and their respective resistors, provide
power management and timing.
; it is controlled via the microprocessor.
The tone key signal, along with the processed audio signal, is then
The battery meter circuit is comprised of U205; LEDs D203, D204,
A 9 Vdc battery provides power to the audio printed circuit board
The 9 Vdc then enters U203, a low dropout 5 V regulator, which
MUTE/
325A1044 (RI)
Characteristics
Shure UC2 Hand-Held UHF Transmitter
ETSI-Approved
This transmitter uses the same pcb as the domestic system, but it
requires a different topology and different parts.
A limiter is inserted between the pre-emphasis and the compressor
to limit the occupied bandwidth.
The buffer after the gain stage, U201A, is now an inverter with
pre-emphasis and 20 dB of attenuation. Previously bypassed, the
expander side of the NE575 (U202) is now activated and used as a
limiter. A sample of the audio is taken from the limiter output, U202,
pin 6, and sent to a control circuit that detects signals above a limiting
threshold. The comparator then sends a control signal to U202, pin 5,
which clamps the signal.
Rf Section
Processed audio enters R320, an internal potentiometer that is
adjusted for 45 kHz deviation (40 kHz for England), 100% modulation,
with a 6.8 dBu 1 kHz tone at the output of the compressor. For J frequencies, R320 is adjusted for 5 kHz deviation with 1 kHz tone injected
into the mic input, to give –23.47 dBu at U201, pin 7 (TPA4).
The audio is then fed to the tuning voltage pin of the voltage controlled oscillator (
locked-loop (
multiplier stages and results in a much higher degree of spectral purity.
The VCO is shielded to prevent external rf fields from affecting its
operation. Regulated 5 Vdc power from the low drop-out regulator,
U311, is provided to ensure frequency stability with changes in battery
voltage.
VCO is capable of tuning from 782 to 806 MHz (FCC-approved),
The
with a 1 to 4 V tuning voltage range. At the output of the VCO, the rf
signal splits into two paths. Frequency variations by country are given
in a table in the
The output of the
pin of the synthesizer, U304. The synthesizer’s internal circuitry divides
the rf signal down, as necessary. The synthesizer contains a quartz-controlled reference oscillator circuit operating from a 4.0 MHz crystal, Y302,
that is adjusted by trimmer C314.
The transmitter output frequency is user-selectable in groups of
compatible channels from 782 to 806 MHz for domestic groups. Frequency selection is made via microprocessor U303, which interfaces with
the user by means of the Group/Channel switches, S301 and S302.
VCO), which modulates the carrier directly . A phase
PLL) frequency-synthesized system eliminates the need for
Service Procedures
VCO is coupled by C323 to the frequency control
section.
Characteristics
The output of the synthesizer is a series of pulses integrated by a
passive loop filter (R316, C319, R317, C353, R318, C320) to produce a
control voltage signal. The control voltage signal is then connected to
VCO through buffer amplifier U306B, which is used to isolate the PLL
the
filter from the audio modulation signals.
4
25A1044 (RI)
Shure UC2 Hand-Held UHF Transmitter
The VCO output is also coupled to the pre-driver and rf power
amplifier through a resistive network (R322, R324, R325) and a
coupling capacitor, C329.
The pre-driver stage, Q302, provides approximately 6 to 8 dB of
gain, which makes up for the pad. R326 and R327 provide base bias
for the transistor, while R328 sets its operating current.
L303 is an rf choke used to provide power to the stage, while L304,
C332, C333, C357, and C2 provide filtering/matching for the stage. The
collector of Q302 feeds into the power amplifier stage via coupling
capacitor C338 and a pi-matching network made up of C339, L305,
and C340.
The rf power amplifier, Q304, is a dual emitter
high-frequency low-noise device can provide +18 dBm out at its 1 dB
compression point. It is biased via base resistors R331 and R332. Its
operating current is controlled via emitter resistor R333.
L306 acts as a choke, and C349, C350, C355, and C356 provide a
good emitter bypass to ground. The amplifier output is matched to lowpass filter U1, via L307. The low-pass filter output couples to the printed
circuit board (pcb) via C347 and L308.
The transmitter can deliver +17 dBm (50 mW) maximum to the
antenna for domestic frequencies; JA and JB frequency transmitters can
deliver +10 dBm maximum to the antenna. During transmitter power-up
and frequency selection, the rf power is muted by bringing the gates of
Q303/Q305 low. This provides approximately 45 dB rf attenuation until
PLL has locked.
the
The transmitter rf is then unmuted by bringing the gates Q303/Q305
high. During transmitter power off conditions, voltage is first removed
from the
of the transmitter is not allowed to drift off frequency during power on/off
conditions.
VCO by bringing the base of Q301 high. Thus, the carrier signal
BJT. This high-gain,
Digital Section
The digital section contains several circuitry blocks.
Microcontroller Section
The microcontroller section consists of the U303 microcontroller.
The rotary switches indicate the UHF frequency group and channel. A
4.000 MHz oscillator provides the operating frequency to the microcontroller. The oscillator circuit includes C300, C301, and Y301. U5, R306,
and C305 form the reset circuit. U5 is the reset IC that resets the U303
microcontroller if the 5 Vdc normal operating voltage falls below 4.3 Vdc.
C302 and C303 form the power supply bypass filter circuit.
525A1044 (RI)
Characteristics
Shure UC2 Hand-Held UHF Transmitter
Memory Section
The memory section consists of U302, a non-volatile, Electrically
Erasable/Programmable Read Only Memory (
mapping of the compatible groups and channels. The microcontroller
serially communicates with this part via data and clock lines to read the
frequency corresponding to the Group and Channel position.
The ability to write to the memory occurs during factory programming
only. During normal usage, this memory is used as a look-up table only.
R335 and R305 resistors allow the clock and data lines to be driven
independently of the microcontroller port pin states during in-circuit programming of the
EEPROM.
Battery Management Section
The U303 microcontroller provides low battery shutdown. The shutdown threshold is 1.88 Vdc ± 10%. A voltage lower than the shutdown
threshold on U303, pin 17, shuts down the transmitter. Resistors R308
and R309 divide down the battery voltage for U303; a battery voltage
less than 5.65 Vdc must shut down the transmitter.
EEPROM) that stores the
This auto shutdown disables the audio tone key mix, mutes the rf
output, and powers down the rf output amplifier section. The current
draw from a 9 Vdc battery in this state is 14 ± 2.0 mA, and the battery
fuel gauge is not functional. Turning off the power switch completely
shuts off the transmitter.
The audio circuit description section provides information for the
battery fuel gauge circuit description.
Rotary Switches for Frequency Selection
A 10-position Group switch (S302) and a 16-position Channel switch
(S301) select the transmitter frequency. Both rotary switches share the
same U303 microcontroller port pins (3 through 6) for a multiplexed
switch read operation. The individual switches are selected by U303,
pins 7 and 8. Resistors R4, R300, R302, and R303 are the pull-ups for
the switch position read. Diode packs D301 through D304 isolate the
switches during the multiplexed read operation.
The multiplexed scheme to read switches does not allow incorporating switch change detection based on interrupts. Also, the switches cannot be constantly scanned to determine changes because the scanning
frequency being in audio range is difficult to filter out.
In a steady state, the switch selector common pins are inputs to the
U303, pins 7 and 8, while U303, pins 3 through 6, are outputs. In this
state, pins 4, 5, and 6 are held low while pin 3 is held high. This forces
logic high level on switch selector 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 U303, pins 7 and 8.
Characteristics
6
25A1044 (RI)
Shure UC2 Hand-Held UHF Transmitter
Any switch change is comprised of state toggle from odd to even,
and vice versa. Only this change is detected, and it is followed by a
multiplexed switch read, in which U303, pins 7 and 8, become selectively
grounded outputs to read the selected switch’s state on pins 3 through 6.
A multiplexed switch read is preceded by tone key and rf mutes.
This mutes the audio in the receiver to allow a quiet change to another
frequency.
For JA frequencies, the Group switch has 16 positions, and the
Channel switch has 10 positions.
Power Switch and Mute Interface
When a transmitter is turned off, the PWRDN signal goes to logic low
on U303, pin 19. This immediately disables the tone key, and the power
hold circuit automatically kicks in to bypass the power switch. This is
followed by 500 mS of delay, and then the rf is muted and turned off.
The power hold circuit is also disabled at this point, and the transmitter
shuts off.
725A1044 (RI)
Characteristics
Shure UC2 Hand-Held UHF Transmitter
Notes
Notes
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8
25A1044 (RI)
Shure UC2 Hand-Held UHF Transmitter
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
Handle
1. Remove the microphone cartridge from the UC2.
2. Use a pair of needlenosed pliers to remove the circuit board
retaining ring from inside the handle.
3. Push the bezel tab-snap in the handle behind the contact pcb to
remove the bezel and switch actuator.
4. Slide the circuit board out by pushing on the battery connectors.
Bezel
Switch actuator
Tab
Tab
Right side view of microphone
Contact pcb
Circuit board subassembly
Figure 3. Bezel Removal
925A1044 (RI)
Functional Test
Shure UC2 Hand-Held UHF Transmitter
ÁÁÁ
Ball screen
Retaining
ring
Rf circuit
board
Microphone
cartridge
Contact
board
(SM58 shown)
Audio circuit
board
Gain control
Handle
Gain control
access
Bezel
Switch
actuator
9 Vdc a lkali ne
battery
Battery cup
Figure 4. UC2 Hand-Held Transmitter , exploded view.
Reassembly
To reassemble the unit, reverse the disassembly steps given above:
1. Slide the circuit board back into the handle.
2. Reinstall the retaining ring, switch actuator, bezel, and the
Disassembly and Assembly
microphone cartridge.
10
25A1044 (RI)
Service Procedures
Measurement Reference
dBu is a measure of
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
Service Equipment Manual
equivalent) is also needed.
Shure UC2 Hand-Held UHF Transmitter
voltage
dB Conversion Chart
, and dBm is a measure of
. The following test equipment (or approved
Table 1
power
Wireless
Test Equipment
.
Equipment T ype Model
Digital multimeter Fluke 87
Rf signal generator Hewlett-Packard 8656B
Frequency counter Hewlett-Packard 53181A
Spectrum analyzer (domestic) Hewlett-Packard 8590L
Spectrum analyzer (JA, JB) Hewlett-Packard 8591E
Shure UC4 receiver Shure UC4
Brass ring for use with test head PT1838–Y
BNC to “rocket launch” cable 95C8418–1
*Audio levels in dBu are marked as dBm on the HP8903B.
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.
Use a BNC to “rocket launch” cable for J frequencies.
2. Keep the test cables as short as possible.
Audio analyzer *Hewlett-Packard 8903B
Test head PT1840
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
1125A1044 (RI)
Service Procedures
Shure UC2 Hand-Held UHF Transmitter
Test Set-Up
P201
P200
D201
C200
J205
RED
S302
TPRF1
GREEN
U200
Q220
RF GND*
J2*
TP18
Q304
R40*
U205
Q202
Q203
Q204
GND
+9V
S200
Q209
TP10
RF SIDE 1
U203
1
1
AUDIO SIDE 1
+5V
Q212
Q201
U501
Y200
C510
Q213
C216
1
TP30
S301
Y302
*J2 and R40 are placed for JA, JB frequencies only. RF GND is accessed thru a hole in the pcb.
C251
C210
Q211
C223
TP4
C221
C213
TP10
Q210
J202
TP2
J201
TP16
C314
Q208
C227
L302
Q301
AUDIO SIDE 2
+9V
TP6
RF SIDE 2
U304
Q303
C315
D302
D301
U5
D304
D303
TP+9
J300
TP30
C303
C324
U306
C353
+5V
C27
U302
R320
C308
C336
C222
C291
Q3
J200
U311
C243
Q305
TP4
TP6
C309
TP+9
TP18
L207
TPRF1
L300
Q2
U201U202
C214
U1U1
U303
Y301
R25
Q1
1
C347
R39
U2
L308
R7
L2
PAD
P204
P203
L1
J301
J302
Service Procedures
Figure 5. UC2 Major Test Component Locations
1. Use the PT1843 cable to connect the audio board to the rf board
through the 11-pin board interconnects (J200, J300, side 2).
2. Apply + 9 Vdc across the battery terminals (J201, J202, side 2).
3. Set the audio GAIN potentiometer (R207, side 1) to minimum,
full counter-clockwise (CCW).
4. See Table 2 for frequency settings.
12
25A1044 (RI)
Shure UC2 Hand-Held UHF Transmitter
Table 2 lists the group carrier frequencies, switch settings,
and tuning voltages for all the alignment tests that follow.
Table 2
Group Carrier Frequencies and Tuning Voltages
(in order by carrier frequency)
Group
Group
Code
Group
Switch
(S101)
Channel
Switch
(S102)
Carrier
Frequency
(MHz)
VCO Tuning
Voltage
(TP130)
Deviation
UA A 4 0 805.500 3.7 45
MB B 1 3 805.500 2.2 15
JA C 0 2 805.500 3.7 5
JB D 4 2 807.500 3.8 5
KK E 5 5 857.125 2.9 15
MC – – – – – –
(kHz)
1325A1044 (RI)
Service Procedures
Shure UC2 Hand-Held UHF Transmitter
C
J2
Alignment
Use this service procedure to correctly align the transmitter’s
operating (output) frequency. C510 tunes the voltage-controlled
oscillator (VCO) to the operating frequency selected, with a 1 – 4 Vdc
tuning range.
C314 adjusts the reference oscillator on the synthesizer, U304.
AUDIO SIDE 1
J205 S200
AUDIO ANALYZER
J205
TEST
HEAD
RF SIDE 2
RETAINING
RING
FREQUENCY COUNTER
TPRF1
C347
CH 2
CH 1
UC2 Transmitter Audio Analyzer Frequency Counter
Power (S200): ON (+9 Vdc) Measurement: AC level Operating freq: See Table 2
Operating freq: See Table 2 Filters: Connect CH 2: TPRF1 and GND
Gain: Minimum Low-Pass (30 kHz): ON For JA,JB frequencies:
High-Pass (400 Hz): ON
onnect to
(pcb rf side 1)
Figure 6. UC2 Frequency Alignment Set-Up
Service Procedures
1. Remove C347 and connect a 50 Ω cable between TPRF1 /
RF GND and a frequency counter.
For JA, JB frequencies, do not remove C347. Connect a
“rocket launch” cable between J2 and the frequency counter.
J2 is only placed on the JA, JB frequency assemblies.
2. Use a PT1840 test head and brass ring (PT1838-Y) to connect
the audio analyzer to the UC2 audio input (J205). Turn ON the
Low-Pass (30 kHz) and High-Pass (400 Hz) filters on the audio
analyzer.
For bench testing, the audio analyzer can be directly connected
to the contact board gold contacts with clip leads.
3. Toggle the power switch, S200, to turn on the UC2 transmitter.
4. Set the UC2 Group and Channel switches, S301 and S302,
according to the group designators on the board and the
settings given in Table 2.
14
25A1044 (RI)
Frequency
C
J2
FREQUENCY COUNTER
Shure UC2 Hand-Held UHF Transmitter
Use this service procedure to correctly align the transmitter’s
operating (output) frequency. C510 tunes the voltage-controlled
oscillator (VCO) to the operating frequency selected, with a 1 – 4 Vdc
tuning range.
C314 adjusts the reference oscillator on the synthesizer, U304.
DC VOLTMETER
+
–
RF GND: FEED THRU
HOLE ON PCB
RF
GND
CH 2
CH 1
S302
RED
S301
GREEN
*R40 and J2 are placed for JA, JB frequencies only.
J2*
R40*
TPRF1
C314
C510
U501
TP30
UC2 Transmitter Frequency Counter
DC Voltmeter
Power: ON (+9 Vdc) Operating freq: See Table 2 Connect + : TP30
Operating freq: See Table 2 Connect CH 2: TPRF1 and GND Connect – : RF GND
Channel switch: See Table 2 For JA,JB frequencies:
Group switch: See Table 2
onnect to
(pcb rf side 1)
Figure 7. UC2 Frequency Test Set-Up
1. Put a dc voltmeter across TP30 (tuning voltage line) and
RF GND.
2. Adjust the
VCO trimmer, C510, until the voltmeter reading
matches the appropriate entry in Table 2, ± 0.125 Vdc.
3. Adjust the variable capacitor, C314, until the frequency counter
measurement matches the appropriate frequency in Table 2,
± 1 kHz.
4. Leave the test cable connected to the rf output.
5. Turn the transmitter OFF.
6. The dc voltmeter can be removed from TP30.
1525A1044 (RI)
Service Procedures
Shure UC2 Hand-Held 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
RF GND: FEED THRU
HOLE IN PCB
S302
RED
S301
GREEN
RF
GND
J2*
TPRF1
R40*
C510
U501
TP30
C314
*R40 and J2 are placed for JA, JB frequencies only.
UC2 Transmitter Spectrum Analyzer
Power: ON Frequency: See Table 2
Operating freq: See Table 2 Span: 200 MHz
Reference voltage: 20 dBm
Peak search: ON
Signal track: ON
Marker: ON
Figure 8. UC2 Power Output Measurement Test Set-Up
1. Remove the BNC cable end from the frequency counter and
connect it to the 50 Ω input of the spectrum analyzer.. Use the
equipment settings shown in Figure 8.
2. Measure the output power. The output power should be:
UA, MB, MC frequencies: 16 + 1 / – 2 dBm
KK frequencies: 14 + 1 / – 2 dBm
For J frequencies, with C347 in place,
adjust R40 to obtain 8.8 ± 0.5 dBm.
3. Turn the UC2 power OFF.
Service Procedures
4. Remove the BNC end of the cable from the spectrum analyzer,
but leave the bare end soldered to the printed circuit board (pcb).
5. For JA, JB frequencies, leave the “rocket launcher” cable
connected.
16
25A1044 (RI)
Shure UC2 Hand-Held UHF Transmitter
Deviation Reference Voltage, Using a UC4 or U4S Receiver
Deviation must be set to make sure the companding systems between the transmitter and receiver correctly track each other. The level
coming out of the transmitter’s audio compressor must match the level
going into the receiver’s audio expander. A fixed gain structure does not
ensure an exact match, primarily because of variations in voltagecontrolled oscillators (VCOs).
This test requires a UC4 or a U4S receiver and is designed to tune
the transmitter regardless of the accuracy of the receiver’s tuning. It is,
however, recommended that a properly-tuned receiver be used to perform the transmitter deviation adjustment.
UC4 RECEIVER (FRONT)
AB
UC4 RECEIVER (BACK)
SQUELCH
S501
(TONE KEY SWITCH)
TK ON TK OFF
AUDIO ANALYZER
RF SIGNAL GENERATOR
UC4 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: –60 dBm
Tone Key (S501): OFF High-Pass (400 Hz): ON Frequency: See Table 2
Group switch: See Table 2 Modulation: See Table 2
Channel switch:
See Table 2
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.
Figure 9. Deviation Reference Voltage Test Set-Up,
Using a UC4 or U4S Receiver
1. Connect the rf signal generator to one of the receiver’s
antenna port B.
2. Turn the UC4 or U4S receiver ON.
3. Set the receiver frequency to match the transmitter frequency.
4. Set the rf signal generator frequency to match the transmitter
frequency.
5. Modulate the generator frequency with 1 kHz audio at a
–60 dBm output level. See Table 2 for deviation.
6. Set the tone key switch (S501 for the UC4, S201 for the U4S)
to the OFF position.
7. Connect the ac voltmeter to the unbalanced output of the
receiver.
8. Read the ac voltage.
Record this voltage. This is the
deviation reference voltage
.
1725A1044 (RI)
Service Procedures
Shure UC2 Hand-Held UHF Transmitter
Deviation Adjustment Voltage: Using a UC4 or U4S Receiver
AUDIO ANALYZER
S501
(TONE KEY SWITCH)
AUDIO
SIDE 1
TPA4 –
U201,
pin 7
UC4 Receiver UC2 Transmitter Audio Analyzer
Output: Unbalanced Power: + 9 Vdc Measurement: AC level
Gain: Maximum Gain: Minimum Frequency Output: 1 kHz
Squelch: Mid Filters:
Tone Key (S501): ON Low-Pass (30 kHz): ON
High-Pass (400 Hz): ON
Figure 10. Deviation Adjustment Voltage Test Set-Up,
Using a UC4 or U4S Receiver, Steps 1 through 3
Reassemble the printed circuit boards for this test.
1. Disconnect the rf signal generator from the UC4 receiver and
return the UC4 tone key switch to the ON position.
2. Connect the audio analyzer output to the MIC input of the
transmitter, using the test head or clip leads to the gold spring
contacts.
3. Adjust the audio input level using the audio analyzer output to
measure the following at TPA4 (U201, pin 7) :
UA MB, MC JA, JB KK
–6.8 dBu ± 0.2 dB
(354 mV ± 1 mV)
– 16.3 dBu
(118 mV ± 1 mV)
– 23.47 dBu
(52 mV ± 1 mV)
– 15.3 dBu
(133 mV ± 1 mV)
Service Procedures
See Figure 11 for equipment set-up and equipment settings for
steps 4 through 6.
18
25A1044 (RI)
Shure UC2 Hand-Held UHF Transmitter
Deviation Adjustment Voltage: Using a UC4 or U4S Receiver
AUDIO ANALYZER
S501
(TONE KEY SWITCH)
VCO
RF
SIDE 1
20 dB
UC4 Receiver UC2 Transmitter Audio Analyzer
Output: Unbalanced Power: + 9 Vdc Measurement: AC level
Gain: Maximum Gain: Minimum Frequency Output: 1 kHz
Squelch: Mid Filters:
Tone key (S501): ON Low-Pass (30 kHz): ON
High-Pass (400 Hz): ON
R320
Figure 11. Deviation Reference Voltage Test Set-Up,
Steps 4 through 6, Using a UC4 or U4S Receiver
4. Connect the unbalanced output of the UC4 to the input of the
audio analyzer (ac voltmeter).
5. Connect the BNC end of the cable from the rf output of the UC2
to the antenna input of the UC4 through a 20 dB in line pad.
6. Turn the transmitter ON and adjust R320 until the ac voltmeter
on the receiver reads the same as the
voltage
, measured above, ± 0.1 dB; or ± 0.2 dB for JA, JB
deviation reference
frequencies..
1925A1044 (RI)
Service Procedures
Shure UC2 Hand-Held UHF Transmitter
Deviation Reference Voltage: Using a Modified SC4 IF Receiver
.
Deviation tests can also be performed using a modified SC4 IF
receiver. For instructions on modifying an SC4 receiver, consult the
Shure
Service Equipment
ZAD–1 MIXER
R
I
L
manual.
ANTENNA INPUT B
MODIFIED SC4 IF RECEIVER
AUDIO OUT
TONE KEY SWITCH: OFF
NOTE: DC VOLTAGES ARE
PRESENT AT MOST RF TEST
POINTS. USE A DC BLOCK
ON THE RF SIGNAL GENERATOR
TO PROTECT TEST EQUIPMENT.
DC BLOCK
RF SIGNAL GENERATOR
AUDIO ANALYZER
SC4 IF 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: + 7 dBm
Tone Key switch: OFF High-Pass (400 Hz): ON Frequency: 10.7 MHz
Operating freq: See Table 2 Modulation: See Table 2
Figure 12. Deviation Reference Voltage Test Set-Up,
Using a Modified SC4 IF Receiver
1. See Figure 12 for equipment test set-up and equipment settings.
2. Connect the rf signal generator output to the input port (L) of a
Zad-1 mixer
Use the same Zad-1 mixer connections for the next adjustment test.
Service Procedures
3. Connect the output port I (intermediate frequency) of the Zad–1
mixer to antenna input B of the SC4 IF receiver.
4. Turn the SC4 IF receiver ON and set the tone key switch on the
front panel of the SC4 IF receiver to OFF.
5. Connect the audio voltmeter to the receiver’s unbalanced output.
6. Measure the output voltage.
Record this voltage. This is the
20
deviation reference voltage
25A1044 (RI)
.
Shure UC2 Hand-Held UHF Transmitter
Deviation Adjustment V oltage: Using an SC4 IF Receiver
AUDIO ANALYZER
TEST HEAD
AUDIO
SIDE 1
TPA4
(U201, PIN 7)
UC2 Transmitter Audio Analyzer
Power: +9 Vdc Measurement: AC level
Gain: Minimum Frequency Output: 1 kHz
Filters:
Low-Pass (30 kHz): ON
High-Pass (400 Hz): ON
Figure 13. Deviation Adjustment Voltage Test Set-Up,
Steps 1 through 5, Using a Modified SC4 IF Receiver
1. Disconnect the rf signal generator from the SC4 IF receiver.
2. Set the SC4 tone key switch on the SC4 front panel to ON.
3. Connect the audio analyzer output to the MIC input of the
transmitter, using the test head or clip leads to the gold spring
contacts.
4. Turn the UC2 power back ON.
5. Adjust the audio input level using the audio analyzer output to
measure the following at TPA4 (U201, pin 7) :
UA MB, MC JA, JB KK
–6.8 dBu ± 0.2 dB
(354 mV ± 1 mV)
– 16.3 dBu
(118 mV ± 1 mV)
– 23.47 dBu
(52 mV ± 1 mV)
– 15.3 dBu
(133 mV ± 1 mV)
See Figure 14 for equipment set-up and equipment settings
for steps 6 through 8.
2125A1044 (RI)
Service Procedures
Shure UC2 Hand-Held UHF Transmitter
Deviation Adjustment V oltage: Using a Modified SC4 IF Receiver
TRANSMITTER
AUDIO
IN
Tone Key switch: ON Low-Pass (30 kHz): ON Modulation: See Table 2
ANTENNA
OUTPUT
NOTE: DC VOLTAGES ARE
PRESENT AT MOST RF TEST
POINTS. USE A DC BLOCK
ON THE RF SIGNAL GENERATOR
TO PROTECT TEST EQUIPMENT.
SC4 IF Receiver UC2 Transmitter Audio Analyzer Rf Signal Generator
Output: Unbalanced Power: + 9 Vdc Measurement: AC level INT: FM
Gain: Maximum Gain: Minimum Output: 1 kHz INT: 1 kHz
Squelch: Mid Filters: Output amplitude: + 7 dBm
ZAD–1 MIXER
R
I
L
DC BLOCK
RF SIGNAL GENERATOR
MODIFIED SC4 IF RECEIVER
ANTENNA INPUT B
TONE KEY SWITCH: ON
AUDIO ANALYZER
High-Pass (400 Hz): ON Frequency: Oper. Freq.
AUDIO OUT
minus 10.7
MHz
Figure 14. Deviation Adjustment Voltage Test Set-Up,
Steps 6 through 8, Using a Modified SC4 IF Receiver
6. Connect the UC2 rf output test cable BNC end to the input port
(R) of the Zad-1 mixer.
7. Connect the rf signal generator, and set the frequency to the
operating frequency (from Table 2) minus 10.7 MHz.
8. Turn ON the UC2 and adjust R320 until the audio voltmeter
connected to the unbalanced output of the UC4 reads the same
as the
deviation reference voltage
, measured above, ± 0.1 dB,
or ± 0.2 dB for JA, JB frequencies..
Service Procedures
22
25A1044 (RI)
Product Specifications
After tuning, the unit should meet the following specifications.
Specification Minimum Typical Maximum
Current drain 50 mA 60 mA 70 mA
Frequency –1.0 kHz See Table 2 +1.0 kHz
Audio freq response @ 100 Hz wrt 1 k –5.0 dB –4.0 dB –3.0 dB
Audio freq response @ 10 Hz wrt 1 k +8.0 dB +9.0 dB +10.0 dB
UA:
System S/N @ 45 kHz, A weighted 95.0 dB 100.0 dB –
Output power, UA, without C347 14.0 dBm 16.0 dBm 17.0 dBm
MB, MC
System S/N @ 1% THD, A weighted 80.0 dB 85.0 dB –
Output power, without C347 14.0 dBm 16.0 dBm 17.0 dBm
KK:
System S/N @ 1% THD, A weighted 80.0 dB 85.0 dB –
Output power, without C347 12.0 dBm 14.0 dBm 15.0 dBm
JA, JB:
System S/N @ 1% THD, A weighted 85.0 dB 90.0 dB –
Output power, at J2, with C347 in place 8.3 dBm 8.8 dBm 9.3 dBm
Shure UC2 Hand-Held UHF Transmitter
2325A1044 (RI)
Service Procedures
Shure UC2 Hand-Held UHF Transmitter
Notes
Notes
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24
25A1044 (RI)
Bench Checks
Dc Problems
Make all dc measurements with respect to the rf ground unless
otherwise specified. Connect the rf and audio printed circuit boards
together via the 11 pin connector, the battery contacts, and the “D” board.
n Make sure the battery voltage is between 6 and 9 Vdc. Make
If incorrect voltage is present:
n Trace the dc back to the voltage regulator .
n Check the biasing resistor values around Q301.
n Check the power switch.
n Look for open coils, cracked parts, reversed polarity capacitors,
Make sure that:
Shure UC2 Hand-Held UHF Transmitter
sure TP+9 has this voltage. Check for the correct Vcc and +5 V
rf at Q301.
or solder shorts. If there is a short to ground from 5 V, try to
isolate different parts of the circuit.
Rf Problems
n The rf OFF signal changes from +5 Vdc at power up and power
down to 0 Vdc during normal operation. Trace the signal to the
microprocessor. Q301 should be saturated during normal
operation.
n Battery voltage appears at TP+9, U311, pin 6. Check for
reversed polarity capacitors, C308 and C309. Check for open
coil, L300.
n If the carrier is out of specification by less than 40 kHz and can-
not be corrected by adjusting C314, put the transmitter on the
operating frequency (see Table 2). Measure and adjust the dc
voltage at TP30. (See Table 2 for frequency variations.) If the
carrier still cannot be trimmed properly, then check C314, C313,
and Y302. If they are correct, replace the synthesizer.
If the carrier frequency is not in the correct frequency range shown in
Table 2, or is unstable, the loop is unlocked.
n Check dc voltage at TP30. If it is 0 V or +5 V, look for a short.
n Check the solder connections at the contact board, VCO, micro
processor (traces LE, D, and CK), and synthesizer U304. If the
connections are good and there is no 4.0 MHz oscillation at
U304, pins 1 and 2, replace the crystal, Y302.
n Check the values and polarity of the loop filter: R316, C319,
R317, C353, R318, C320, C354, U306B, R319, R320, and
R321. Check the bias voltage of U304, pins 3 and 4, and
U306B, pin 8. As a last resort, replace the synthesizer, U304.
2525A1044 (RI)
Bench Checks
Shure UC2 Hand-Held UHF Transmitter
Low Rf Output Power
n Check the polarity/soldering of the output low-pass filter, U1.
(Rf IN is marked with a dot.)
n Check for opens or shorts on output coil L308.
n Check the polarity of Q304.
n Verify the dc bias of Q302 and Q304. Check L303, L304, and
L306, if no bias. Verify that the rf MUTE signal changes from
0 Vdc at power up and power down to +5 Vdc during normal
operation. If Q303 and Q305 are not in a low impedance state
during normal operation, the rf power at the antenna port will be
attenuated by about 45 dB.
n Check for missing ground connections.
n Check the dc level at the VCO Vcc pin. If no dc power,
check L302.
n Verify the VCO output power.
n Partially isolate the VCO from the rest of the circuit by removing
C323. The carrier frequency will no longer be locked, but the
output power from the VCO should be around –1 ± 2 dBm into a
50 Ω load.
n If the power out of the VCO is still low, the problem is in the VCO.
n Check the values of R322, R323, R324, R325, and C329.
n Isolate components starting from the antenna and working back
to the rf power amp.
n Check the values/continuity of the input and output matching net-
works for Q302, Q304 (C329, C338, L305, C339, C340, L307).
n Check the values of the bypass capacitors C357, C2, C332,
C333, C334, C335, C360, C341, C342, C349, C350, C355,
C356.
n As a last resort, replace Q302 or Q304.
Excessive Current Drain
n Try isolating different sections of the circuit: rf, audio, digital.
Look for reversed polarity capacitors or wrong resistor values.
Check the voltage regulators.
Deviation Problems
n If R320 cannot be adjusted to obtain the deviation reference
voltage (see the
problem to the audio or rf section. Check the value of R320. To
check the rf section, set the transmitter frequency (see Table 2),
and verify the tuning voltage of the VCO.
n Check the audio section by applying audio to the mic input. With
an oscilloscope, make sure audio is present at TPA7. If not,
work backwards towards the input.
Bench Checks
Service Procedures
26
section), try to isolate the
25A1044 (RI)
Audio Problems
Shure UC2 Hand-Held UHF Transmitter
No Tone Key
No tone key means that the 32.768 kHz tone key sidebands are not
visible when the carrier is viewed on a spectrum analyzer. If tone key
levels are there but are too low, the deviation is off and needs to be
recalibrated. They should be, roughly, –23 dBc ± 3 dB.
n Apply a 1 kHz tone at a level of 0 dBu to the audio input with the
audio gain pot at minimum.
n If the carrier on the spectrum analyzer does not show any devi-
ation, check part integrity and audio path continuity between
U201, pin 14, and the VCO.
n If the spectrum analyzer shows a deviated carrier, probe for a
32 kHz signal at TPA6 and I209 and continue to the next step.
n If there is a signal at I209 but not at TPA6, then the mute circuit
through Q211 is being activated. Verify that the logic signal at
Q211, pin 1, is logic low. If it is low, replace Q211. If it is not low,
check the line for a short to +5 V. If there is no short, the microprocessor is defective and must be replaced.
n If there is a 32 kHz signal at both I209 and TPA6, replace R236.
n If there is not a 32 kHz signal at either I209 or TPA6, there is
something wrong with the tone key circuit or the tone key supply
voltage. If the tone key supply voltage (U200, pin 8) is less than
2 V, there is a problem with one or more of the following components: R261, R264, R265, R266, C238, Q220, C237, R232,
or R260.
n If the voltage at U200, pin 8, is greater than 2 V, the problem is in
the tone key circuit itself. Check for shorts and opens. Replace
parts in this circuit beginning with the crystal until the 32 kHz
oscillation returns.
No Audio
n View the carrier on the spectrum analyzer. If there are not
32 kHz tone key sidebands around the carrier, follow the steps
above for “No Tone Key.”
n Verify +9 V, half-supply bias, and ground connections to U200.
n Verify +9 V, half-supply bias, and ground connections to U201.
n Follow the audio path from where audio is applied until the point
of discontinuity is reached and replace the appropriate part.
2725A1044 (RI)
Bench Checks
Shure UC2 Hand-Held UHF Transmitter
Notes
Notes
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28
25A1044 (RI)
Shure UC2 Hand-Held UHF Transmitter
Replacement Parts and Drawings
Parts Designations
The following comments apply to the parts list and the schematic:
Resistors: Unless otherwise noted, all resistors are surface-mount
0603 size, 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.
Table 3
UC2 Model Frequency Variations
Printed Circuit Boards
(in order by frequency)
Country
Code
MC Netherlands 774 – 782 MHz 90MC8792J
UA U.S.A. and Canada 782 – 806 MHz 90UA8792J
JA Japan 797 – 806 MHz 90JA8792J
MB Europe 800 – 830 MHz 90MB8792J
JB Japan 806 – 810 MHz 90JB8792J
KK United Kingdom 838 – 862 MHz 90KK8792J
Country
Designation
Frequency
Range
UC2 Printed
Circuit Board #
Table 4
Replacement Parts
Reference
Designation
MP1 Actuator 65B8298
MP2 Battery snap (positive) 56A317
MP3 Battery snap (negative) 56A318
MP4 Bezel 65A8299
MP5 Compression disc (in battery cup) 38A180
MP6 Contact (on contact pcb) 53D2039
MP7 Cup 65A8300A
MP8 Handle 65A8301A
MP9 Interconnect strip 56D8074
MP9 Nameplate, bottom 39–8302
MP10 Nameplate, handle 39–8303
Description
Shure Part
Number
2925A1044 (RI)
Replacement Parts and Drawings
Shure UC2 Hand-Held UHF Transmitter
Printed Circuit Board Replacement Parts
Reference
Designation
C314 Capacitor, trim, 5 – 40 pF 152F03
C510 Capacitor, trim, 1 – 3 pF 152A04
D201 Diode, signal / switching, SMD, SOT-23, 1.1 V 184A08
D203 LED, red 184A18
D204 LED, yellow 184B18
D205 LED, green 184C18
D301–304 Diode, dual switching, SOT-23, 1 V 184A07
D501 Diode, rf tuning 184A36
J200 Connector, receptacle, 11-pin header, female 170A08
J205 Socket, strip 170C15
J300 Connector, 11-pin header, male 170A07
L1 Bead, ferrite 162A12
L200,203,207,
300,32,303,306
L304 Inductor, 8.2 nH 162W10
L305 Inductor, 3.3 nH 162T10
L307 Inductor, 22 nH 162D10
L308 Inductor, 6.8 nH 162V10
L501,503 Inductor, 100 nH 162A25
L502 Inductor, 10 nH 162N25
Q3,201,211,212,
213
Q202 Transistor, chopper, PNP, SOT-23 183A07
Q203,303,305 Transistor, SMD, power MOSFET 183A46
Q204,208,209,
210,220
Q301 Transistor 183A01
Q302,501,502 Transistor 183A48
R207 Potentiometer, Gain 46H8014
R320 Potentiometer, Trim, 1 k 146B02
S200 Switch, slide, DPDT 55A178
S301 Switch, Dip, PCB, 16 pos 155A11
S302 Switch, DIP, PCB, 10 pos 155B11
U5 Detector, SMD voltage 188C210
U107,108, 109 Filter, low-pass 162A28
U31 1 IC voltage regulator, 5V 188A1 15
U200,201 IC, quad op amp 188A49
U202 IC, compandor, low voltage 188A126
U203,311 IC voltage regulator, 5 V 188A115
U205 IC, comparator, quad, ultra-low power 188A123
U302 IC, EEPROM 188A131
U303 Microprocessor , programmed 188D238E
U304 PLL frequency synthesizer 188A265
U306 Amplifier, operational, dual, SMD 188A118
U501 Dielectric resonator 140A14
Y200 Crystal, 32.768 kHz 40A8010
Y301,302 Crystal, 4.0 MHz 40A8012
Inductor, 180 nH 162R10
Transistor, SMD, SOT–23, FET, TMOS 183A30
Transistor, SOT-23, NPN 183A02
Table 5
Description
Shure Part
Number
Replacement Parts and Drawings
30
25A1044 (RI)
Shure UC2 Hand-Held UHF Transmitter
Table 6
Group Designators
(in order by frequency)
Frequency
Range
(MHz)
774–782 Netherlands MC – 1.0 – – – –
782–806 U. S. & Canada UA 1.0 – – – – –
797–806 Japan JA – – 1.0 – – –
800–830 Europe MB – 1.0 – – – –
806–810 Japan JB – – – 1.0 – –
838–862 England KK – – – – 1.0 –
Country
Code
MC – – – 1.0 – – – – – –
UA – – 1.0 – – – – – – –
JA – – – – 1.0 – – – – –
MB – – – 1.0 – – – – – –
JB – – – – – 1.0 – – – –
KK – – – – – – 1.0 – – –
Country
Designation
R28ΩR29ΩR30kΩR31kΩR32kΩR33kΩR34kΩR35kΩR36ΩR37
Country
Code
R19kΩR20kΩR21kΩR22kΩR26kΩR27
kΩ
Ω
3125A1044 (RI)
Replacement Parts and Drawings
Shure UC2 Hand-Held UHF Transmitter
Frequency Dependent Parts
Table 7
(in order by frequency)
Frequency
Range (MHz)
774–782 Netherlands MC .047 0.1 220 2.2 – – – 27
782–806 U. S. & Canada UA – – – – .047 – – 27
797–806 Japan JA .047 0.1 220 2.2 – – 10 4.7
800–830 Europe MB .047 0.1 220 2.2 – – – 27
806–810 Japan JB – – – – .047 – 10 4.7
838–862 England KK .047 0.1 220 2.2 – – – 27
Country
Code
MC 4.7 4.7 4.7 1.0 – – 183A01 183A02 249 10.0
MB 4.7 4.7 4.7 1.0 – – 183A01 183A02 249 10.0
Country
Code
MC 1.5 10.0 4.02 10.0 100 1.0 10.0 22.1 1.0 – –
MB 1.5 10.0 4.02 10.0 100 1.0 10.0 22.1 1.0 – –
Country
Designation
C505pFC506pFC507pFC509
UA 4.7 4.7 4.7 1.0 – 162A12 – – – –
JA 4.7 4.7 4.7 1.0 95A8278 – 183A01 183A02 249 10.0
JB 4.7 4.7 4.7 1.0 95A8278 162A12 – – – –
KK 3.9 2.2 3.9 – – – 183A01 183A02 249 10.0
R3kΩR6kΩR7kΩR8kΩR9kΩR10MΩR11kΩR12kΩR13MΩR16kΩR40
UA 0 – – – – – – – – 0 –
JA 1.5 4.02 4.02 4.02 100 1.0 10.0 22.1 1.0 – 146B02
JB 0 10.0 – – – – – – – 0 146B02
KK 1.5 10.0 4.02 10.0 100 1.0 10.0 22.1 1.0 – –
Country
Code
C4uFC24uFC35pFC210uFC211uFC254uFC330pFC345
pF
J2 L2 Q1 Q2
R1kΩR2
pF
kΩ
kΩ
Country
Code
MC – 15 24.9 200 0 – 100 155A11 155B11 188A136
UA – 15 24.9 200 10.0 4.02 100 155A11 155B11 –
JA 100 20 – 24.9 0 – 249 155B11 155A11 188A136
MB – 15 24.9 200 0 – 100 155A11 155B11 188A136
JB 100 20 – 24.9 10.0 4.02 249 155A11 155B11 –
KK – 15 24.9 200 0 – 100 155A11 155B11 188A136
R42kΩR233kΩR264kΩR265kΩR287kΩR289kΩR333
Replacement Parts and Drawings
32
S301 S302 U2
kΩ
25A1044 (RI)
Shure UC2 Hand-Held UHF Transmitter
Printed Circuit Board, Side 1
UC2 Hand-Held UHF Transmitter
3325A1044 (RI)
Replacement Parts and Drawings
Shure UC2 Hand-Held UHF Transmitter
Replacement Parts and Drawings
34
Printed Circuit Board, Side 2
UC2 Hand-Held UHF Transmitter
25A1044 (RI)
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