Shure U4D Service Manual

Shure Brothers Incorporated
222 Hartrey Avenue
Evanston IL 60202-3696 U.S.A.
UHF Wireless System
E2000, Shure Incorporated Printed in U.S.A.
25–1062–2 (TD)
SERVICE MANUAL CHANGE NOTICE
UHF WIRELESS RECEIVER MODEL U4D
Changes and corrections have been made to the Service Manual for the U4D UHF Wireless Receiver.
These changes will make it easier to properly align the receivers. 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.
U4D SERVICE MANUAL REVISION HISTORY
Release Part Number Date Code
Original 25A1062 QE
Revision 1 25B1062 QK
Revision 2 25C1062 SB
Revision 3 25D1062 TD
Revision 4 25D1062 TL
Revision 5 25D1062 AG
CHANGES EFFECTIVE JULY, 2001
REMOVE
these pages from the U4D Service Manual
INSERT
these Revisionpages into the U4D Service Manual
35–40 35–40

Shure U4D Specifications

General

Type	Diversity Receiver
Tuning Steps	25 kHz
Modulation	FM
Image Rejection	>70 dB
Spurious Rejection	>70 dB
Dynamic Range	>100 dB
Total Harmonic Distortion	< 0.5%
Audio Output	Balanced XLR, Unbalanced 1/4"
Power Requirements	12 - 18 V DC
Dimensions	1.7 x 1.75 x 6.5 in

Summary

Circuit Description

Audio Section

Preliminary Tests

Tests and Procedures

Functional Tests

Disassembly and Assembly

Safety and Top Cover Removal

Front Panel Removal

Component Removal and Reassembly

Service Procedures and Product Changes

Test Equipment Requirements

Alignment Procedures

Alignment Test Setup

RF Tuning and Voltage Verification

Procedures for verifying DC voltages at antenna inputs and RF tuning steps for Channel A.

Local Oscillator Frequency Alignment (Channel A)

Procedure to align the local oscillator frequency using a spectrum analyzer or frequency counter.

FM Detector Quadrature Coil Alignment (Channel A)

Steps to tune the quadrature coil (L310 or FL311) for maximum audio output.

Second Mixer Coil Alignment (Channel A)

Procedure to adjust L313 for maximum DC voltage at specific IC pins.

THD and RSSI Adjustment (Channel A)

Measures total harmonic distortion and adjusts RSSI levels for Channel A.

Noise Set-Up (Channel A)

Aligns channels for signal-to-noise ratio by matching respective DC levels.

FM Detector Quadrature Coil Alignment (Channel B)

Steps to tune the quadrature coil (L304 or FL313) for maximum audio output.

Second Mixer Coil Adjustment (Channel B)

Procedure to adjust L324 for maximum DC voltage at specific IC pins.

THD and RSSI Adjustment (Channel B)

Measures total harmonic distortion and adjusts RSSI levels for Channel B.

Audio Level Setup (Channel B)

Procedure to set audio levels for various models by adjusting R250.

Audio Level Setup (Channel A)

Procedure to set audio levels for various models by adjusting R203.

Tone Key Filter Alignment

U4D Receiver 2 Alignment

Replacement Parts and Drawings

U4D Receiver Replacement Parts