Shure uc1 Service Manual

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

UC UHF Wireless System

SERVICE MANUAL CHANGE NOTICE

UC1 UHF BODY-PACK TRANSMITTER

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

CHANGES EFFECTIVE [DATE]

REMOVE

these pages from

your current manual

Revision 1 ALL Revision 2 ALL

Revision 2 pages:13,15,17,20,22,27,29 and 30 Revision 3 pages:13,15,17,20,22,27,29 and 30

the following revised pages

attached to this notice

INSERT

SERVICE MANUAL REVISION HISTORY

Release Part Number Date Code

Original 25A1043 RI
Revision 1 25B1043 SB
Revision 2 25C1043 TB
Revision 3 25C1043 TK

E1999, Shure Incorporated

Printed in U.S.A.

UC1 / UC1L Body-Pack Transmitter

Characteristics

General

The Shure UC1/UC1L Body-Pack Transmitter is microprocessor­controlled, operating in the 692–716 MHz and 774–862 MHz frequency
ranges. The UC1/ UC1L is used in mid-level installed sound, rental, and
concert sound applications. Six frequency range variations are available.

Controls and Connectors

4

3

2

1

Service Manual

25C1043 (TK)

11

1. Antenna

2. Power/Battery Fuel Gauge LEDs

3. Power ON/OFF Switch

4. Input Connector

5. Rf/Audio Mute Switch Input Connector

6. Input Attenuation Control
Figure 1. UC1 Controls and Connectors

Service Note: Shure recommends that all service procedures be performed by a Factory­Authorized 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.

8

10

9

7

12

7. Audio Gain Control

8. Group Rotary Switch

9. Channel Rotary Switch

10. Battery Compartment

11. Battery Cover Release Tabs

12. Battery Compartment Cover

5

6

E2000, Shure Incorporated Printed in U.S.A.

25C1043 (TK)

Shure UC1 Body-Pack UHF Transmitter

Circuit Description

LIMITER CONTROL INPUT

MIC. /

INSTR.

FROM
BATT.

REMOTE

MUTE

ON / OFF

SWITCH

FET

BYPASS

MIC. /

INSTR.

+5V

REG.

OFF / MUTE DETECT

+5v

UNREG. PWR.

PLL CONTROL

LIMITER

CONTROL OUTPUT

TONE KEY

CIRCUIT

TONE CONTROL

MCU

TONE KEY

BATTERY

MGMT.
& FUEL

GAUGE

Σ

CALL ID

EEPROM

(MEM)

AUDIO

OUT

CONTROL

PWR.

HOLD

CIRCUIT

Audio Section

Domestic Models

SYNTH.

GROUP CHANNEL

RF POWER

AUDIO IN

VCO

RF MUTE RF MUTE

Figure 2. UC1 Circuit Block Diagram

The audio signal enters the audio board at J204, pin 1. The signal
then enters a switchable 20 dB pad made up of SW203, R203, R204,
C204, and C206. The back-to-back diodes, U206, are used to keep
the op-amp from snapping to the rail and reverse-phasing when the
maximum input voltage range is exceeded.

Circuit Description

The signal is ac-coupled through C205 into a 40 dB (30 dB for
J frequencies) user-adjustable gain stage around amplifier U2. This
gain stage is externally accessible to the user. Due to its topology, it is
a unique stage because it is non-inverting and allows for a gain less than
unity. Resistors R205 and R207 set up a half-supply bias, and R206 sets
the ac input impedance.

The amplified audio signal then passes through a pre-emphasis
network before entering the compression stage. R221, R222, C215,
and C216 set up two corners for the pre-emphasis network. The pre­emphasis network feeds the NE575 compander, U203, which utilizes

2

25C1043 (TK)

Shure UC1 Body-Pack UHF Transmitter

an external amplifier, U202B. U203 performs a 2:1 logarithmic compres­sion of the audio signal.

Transistors Q201 and Q202, with crystal Y201, form the tone key
oscillator circuit that provides a stable, continuous 32.768 kHz sine
wave. 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.
If the tone key or the transmitter is turned off, the receiver is muted.

Q211 acts as a switch for toggling the tone key ON/OFF. It is con-
trolled from the microprocessor, via the TONEMUTE0 signal. The tone
key signal, along with the processed audio signal, is then fed to a sum­ming amplifier, U201A. After passing through the ac coupling capacitor,
C240, the signal is then fed to the rf module.

The battery meter circuit is comprised of comparator U208 and

LEDs D201, D202, D203, and various resistors. When the battery circuit

is less than 6.5 Vdc, the output of U208, pin 13, changes low, the red

LED illuminates, and the tone-key level increases. The receiver then

utilizes the amplitude of the tone-key to indicate that the transmitter
battery is low.

ETSI Models

Rf Section

A 9 Vdc battery provides power to the audio printed circuit board
(pcb) through switch SW202.
battery protection. 9 Vdc enters U205, a low-dropout 5 Vdc regulator,
and gives a clean regulated 5 Vdc supply to run the audio circuitry.

This transmitter uses the same board as the non-ETSI system,
except that 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 U203 is now activated
and used as a limiter. A sample of the audio is taken from the limiter
output (U203, pin 6) and sent to a control circuit which detects signals
from a limiting threshold.

The comparator then sends a control signal to U202, pin 5, which
clamps the signal.

Processed audio enters R149, an internal potentiometer that is
adjusted for 45 kHz deviation (100% modulation for UA, MA, and MB
frequencies), with a –7.2 dBV (0.355 Vrms) 1 kHz tone at the output
of the front audio stage (U201, pin 1). For KK frequencies, R243 is
adjusted for 40 kHz deviation. For JB frequencies, R149 is adjusted for
5 kHz deviation with –63.2 dBV, 1 kHz tone at the input to the transmitter.

FET Q217 provides electrical reverse

25C1043 (TK)

3 Circuit Description

Shure UC1 Body-Pack UHF Transmitter

The audio is then fed to the tuning voltage pin of the voltage-

controlled oscillator (

VCO) and modulates the carrier directly.

Using a phase-locked loop (

PLL) frequency synthesized system

eliminates the need for 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 is provided to ensure frequency stability with

changes in battery voltage.

VCO can tune from 782 MHz to 810 MHz with a 1 Vdc to 4 Vdc

The
tuning voltage range; different VCOs are required for MB and KK frequen-
cy models. At the output of the

The output of the

VCO is coupled by C134 to the frequency control

VCO, the rf signal splits into two paths.

pin of the synthesizer, U104, pin 8. The internal circuitry of the synthe­sizer divides the signal, as necessary, to the desired reference frequency
of 125 kHz. The synthesizer contains a reference oscillator circuit oper­ating from a 4.0 MHz quartz crystal, Y101, that is adjusted by trimmer
C123. The transmitter output frequency is user-selectable in 125 kHz
increments, from 782 MHz to 806 MHz. Frequency range and increment
size vary for each model.

Frequency selection is made via microprocessor U101, which inter­faces the user by means of the mode/select switches. The output of the
synthesizer is a series of pulses which are integrated by a passive loop
filter, R121, C130, R122, C129, C130, R123, and C132, to produce a
control voltage signal. The control voltage signal is then connected to

VCO through amplifier U106A, which is used to isolate the PLL filter

the
from the audio modulation signals.

The

VCO output is also coupled to an rf power amplifier through a

resistive pad consisting of R127, R128, R129, and R130. The signal is
then low-pass filtered through U107. The signal is coupled through C144.

Transistor Q102 acts as an rf pre-amplifier stage with typically 8 dB
of gain. R131, R132, and R133 provide dc bias to Q102. C145, C146,
C147, C149, C150, and L111 are used to decouple the rf off the emitter
of Q102, Vcc, and +9 Vdc supply voltages.

C152 couples the output of Q102 to low-pass filter U108. The signal
is then low-pass filtered through U108, and then coupled through C157.

Q104 acts as an rf amplifier stage with typically 16 dB of gain. L110,
R136, R137, and R138 provide dc bias to Q102. C160, C161, C162,
C163, C164, C165, and L114 are used to decouple the rf off the emitter
of Q104, Vcc, and +9 Vdc supply voltages.

L115 and C167 match the output of Q104 to low-pass filter U109.
The signal is coupled through C173 to the output antenna, W101.

The transmitter can deliver a maximum of +17 dBm (50 mW) to
the 50Ω antenna. During transmitter power-up and frequency selection,
the rf power is muted by bringing the gate of Q103 and Q105 high. The

RFUNMUTE signal is 5 Vdc. This provides approximately 45 dB rf attenu-

ation until the PLL has locked.

Circuit Description

4

25C1043 (TK)

Shure UC1 Body-Pack UHF Transmitter

The transmitter is unmuted by bringing the gate low (
During transmitter power OFF conditions, the rf power is first muted by
bringing the base of Q103 and Q105 high. When the rf is muted this
way, the carrier signal of the transmitter is not allowed to drift off
frequency during power

When the external mute switch is closed, the ring and sleeve on the
jack are connected, or the tip and sleeve can be connected, depending
on how the switch is wired.

If the tip is connected to the sleeve, this grounds the IRQ signal
line that is connected to the microprocessor. Then, the 33 kHz tone key
signal is muted (
bringing the base of Q103 and Q104 high (RFMUTE1). Finally, the rf
power is then turned off via the
the Vcc line to the VCO and the last rf amps.

If the ring is connected to the sleeve, this grounds the

TKMUTE1 grounds Q4 at the output of the tone key oscillator circuit.

The
This mutes the audio signal immediately.

Transmitter Display Board

RFUNMUTE).

ON or OFF conditions.

TONEMUTE1). The transmitter rf power is muted by

RFOFF1 signal. This is done by reducing

TKMUTE1.

UHF Body-Pack Transmitter Digital Section

The digital section contains several circuitry blocks.

Microcontroller Section

The microcontroller section consists of a U101 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 C117, C118, and Y102. U103, R106, and
C120 form the reset circuit. U103 is the reset IC that resets the U101
microcontroller if the 5 Vdc normal operating voltage falls below 4.3 Vdc.
R115 and C119 form the power supply filter circuit.

Memory Section

The memory section consists of U102, a non-volatile Electrically
Erasable / Programmable Read Only Memory (
mapping of 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. Ability to write to
this memory occurs during factory programming only.

During normal usage, this memory is used as a look-up table only.
Additional detail about the contents of
ing sections.

EEPROM is covered in the follow-

EEPROM) that stores the

25C1043 (TK)

R103 and R108 resistors allow the clock and data lines to be driven
independently of the microcontroller port pin states during in-circuit
programming of

EEPROM.

5 Circuit Description

Shure UC1 Body-Pack UHF Transmitter

Battery Management Section

The microcontroller provides for low battery shutdown. The shut­down threshold is 1.88 Vdc ± 10%. A voltage lower than the shutdown
threshold on pin 17 of the U101 microcontroller shuts down the transmit­ter. Resistors R104 and R105 divide down the battery voltage for the
microcontroller. A battery voltage of less than 5.65 Vdc shuts down the
transmitter.

This auto shutdown disables the audio tone key mix, mutes the rf
power output, and power downs the rf output amplifier section. The cur­rent draw from a 9 Vdc battery in this state is 45 mA, and the battery fuel
gauge is functional. Turning off the power switch must completely shut
off the transmitter.

The audio circuit description provided the battery fuel gauge circuit
description.

Rotary Switches for Frequency Selection

A 10-position Group switch, S101, and a 16-position Channel switch,
S102, select the transmitter frequency. Both rotary switches share the
same U101 microcontroller port pins, 3 through 6, for a multiplexed
switch read operation.

Pins 7 and 8 of the U101 microcontroller select the individual
switches. Resistors R109 through R112 are the pull-ups for the switch
position read. Diode packs D101 through D104 isolate the switches dur­ing a multiplexed read operation.

The multiplexed switch read system does not allow 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
U101 microcontroller pins 7 and 8. 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 a
logic high level on the switch selector pins if the switches are set on odd
positions. If the switches are set on even positions, the contact on pin 1
is open from the switch common pin, and the pull-down resistors, R114
and R115, force the logic low to pins 7 and 8 of U101.

Any switch change is made by a state toggle from odd to even, or
vice versa. Only this change can be detected and is followed by a multi­plexed switch read. In this case, U101 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.

Circuit Description

6

25C1043 (TK)

Shure UC1 Body-Pack UHF Transmitter

Power Switch and Remote Mute Switch Interface

When a transmitter is turned off, the
on U101, pin 19. The same signal is also forced low when a remote
mute switch closes the tip contact to the sleeve ground.

The microcontroller treats both of these events in a similar manner.
It immediately disables the tone key, and the power hold circuit auto­matically kicks in to bypass the power switch. Followed by 500 msec.
of delay, the rf is muted and also turned off.

The power hold circuit is also disabled at this point. If it is the power
off condition, then the transmitter is shut off. Otherwise, it is the remote
mute condition, and the transmitter waits here for unmute to occur.

PWRDN1 is pulled up back to logic high level when unmute occurs.

The rf section repowers and is unmuted, followed by tone key enable
to completely recover from the remote mute condition. When a remote
mute switch closes the ring contact to the sleeve ground, the
signal goes to a logic low that immediately mutes the audio.

PWRDN1 signal goes to logic low

TKMUTE1

25C1043 (TK)

7 Circuit Description

Shure UC1 Body-Pack UHF Transmitter

Notes

Circuit Description

This page intentionally left blank.

8

25C1043 (TK)

Shure UC1 Body-Pack UHF Transmitter

Functional Test

Verify operation and reported malfunction, referring to the product
User 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

1. Open the battery compartment and remove the battery.

2. Remove the belt clip.

3. With the battery compartment open, remove the four screws
from the back of the case.

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

5. Lift the pcbs out of the transmitter case.

Figure 3. UC1 Disassembly

25C1043 (TK)

9 Disassembly