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

Service Manual

UHF Transmitter

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

541

screw-on removable antenna. .

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)

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

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)

Preliminary Tests

Shure U1/U1L Body-Pack UHF Transmitter

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)

Disassembly and Assembly

+ 23 hidden pages