Shure U2 Service Manual
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Shure U2 Service Manual

Hand-held uhf transmitter
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SERVICE MANUAL CHANGE NOTICE
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
Original
Revision 1
Revision 2
Revision 3
CHANGES EFFECTIVE JULY 2, 2001
REMOVE
these pages from the
U2 Service Manual
E2000 Shure Incorporated
25–1022–2 (AG)
U2 HAND-HELD TRANSMITTER
Part Number
22
Shure Incorporated
222 Hartrey Avenue
Evanston IL 60202-3696 U.S.A.
UHF Wireless System
25A1022
25B1022
25C1022
25C1022
these Revised pages into the
U2 Service Manual
Date Code
QE
SA
TD
AG
INSERT
22
Printed in U.S.A.

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  • Page 1 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.

  • Page 2: Controls And Indicators

    10. Audio Gain Control 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.

  • Page 3: Circuit Description

    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 through C201 into a 26 dB user-adjustable gain stage around U201B. This gain stage is externally accessible to the user. C249, C250, and C209 protect the preamplifier and bias circuits from rf interference.
  • Page 4 Shure U2 Hand-Held UHF Transmitter ence from external rf fields. Regulated 5 Vdc power from the dc/dc con- verter 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.
  • Page 5 Shure U2 Hand-Held UHF Transmitter operating frequency to the microcontroller. The oscillator circuit includes 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.

  • Page 6: Preliminary Tests

    Shure U2 Hand-Held UHF Transmitter Preliminary Tests Test Component Locations BOTTOM DIGITAL DISPLAY BOARD R227 location for G and later board versions. R227 location for F and earlier board versions. BOTTOM RF-AUDIO BOARD Figure 2. Test Component Locations 25B1022 (AG)

  • Page 7: Listening Test

    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.

  • Page 8: Frequency Response

    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.
  • Page 9 Shure U2 Hand-Held UHF Transmitter Notes This page intentionally left blank. Notes 25B1022 (AG)

  • Page 10: Disassembly And Assembly

    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.
  • Page 11 Shure U2 Hand-Held UHF Transmitter Notes This page intentionally left blank. Notes 25B1022 (AG)

  • Page 12: Service Procedures

    Shure U2 Hand-Held UHF Transmitter 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.

  • Page 13: Antenna Replacement

    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.

  • Page 14: Test Equipment

    *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.
  • Page 15 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.
  • Page 16 Shure U2 Hand-Held UHF Transmitter Rf Alignment VC201 FREQUENCY COUNTER J103 U2 Transmitter 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.

  • Page 17: Audio Alignment

    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 frequency as the U2. 5. Set the rf signal generator internal FM tone to 1 kHz modulation.
  • Page 18 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.
  • Page 19 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.
  • Page 20 Shure U2 Hand-Held UHF Transmitter 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- ments with respect to rf ground unless otherwise specified). if incorrect voltage is present, check the biasing resistors values.
  • Page 21 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.

  • Page 22: Model Variations

    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.

  • Page 23: Parts Designations

    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 with rating and 1% tolerance. Capacitors: Unless otherwise noted, non-polarized capacitors are surface-mount dielectric types with a 100 capacity and a 5% tolerance, and polarized capacitors are tantalum types.
  • Page 24 Shure U2 Hand-Held UHF Transmitter Table 5 Printed Circuit Board Replacement Parts: Side 1 Reference Shure Part Designation Description Number Non-SMT Components J101,102 Socket strip (for LCD) 56G8068 P101 Battery contact (positive terminal) 56A8061 R208 Audio gain potentiometer, 0.1 W, 20%, 20 k...
  • Page 25 Shure U2 Hand-Held UHF Transmitter Table 6 Printed Circuit Board Replacement Parts: Side 2 Reference Shure Part Designation Description Number Non-SMT Components J103 Antenna connector, SMC 95A8641 SMT Components D203,204 Diode, dual 184A08 20%, 0.12 µH L202 Inductor 162A10 10%, 0.18 µH...
  • Page 26 Shure U2 Hand-Held UHF Transmitter Notes This page intentionally left blank. 25B1022 (AG) Replacement Parts and Drawings...
  • Page 27 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)
  • Page 28 Shure U2 Hand-Held UHF Transmitter U2 Hand-Held Transmitter Digital Display Printed Circuit Board Legend “G” and Later Board Versions 25B1022 (AG) Replacement Parts and Drawings...
  • Page 29 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)
  • Page 30 Shure U2 Hand-Held UHF Transmitter U2 Hand-Held Transmitter Rf-Audio Printed Circuit Board Legend “G” and Later Board Versions 25B1022 (AG) Replacement Parts and Drawings...
  • Page 31 Shure U2 Hand-Held UHF Transmitter U2 Hand-Held Transmitter Microphone Head Board Replacement Parts and Drawings 25B1022 (AG)
  • Page 32 Shure U2 Hand-Held UHF Transmitter Notes This page intentionally left blank. 25B1022 (AG) Notes...

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