Service Procedures - Shure U4D Service Manual

Service Procedures

Product Changes
New Volume Control Knobs and Potentiometers
PRINTED CIRCUIT
BOARD REVISION
"G" or earlier
"H" or later
New Digital Display Board Pushbutton Actuators
New PCB layout, component changes and designations
Service Procedures
Shure U4D Dual Diversity UHF Receiver
The following changes have been made to the U4D receiver.
The new potentiometers cannot be used on old boards, and the new
knob assembly cannot be used with old potentiometers.
R110 VOLUME CONTROL
POTENTIOMETER PART NO.
The old actuators cannot be used on newer display boards. If for
any reason the display board is replaced, the actuators must also be
updated. However, any revision display board can be mixed with any
revision rf–audio board. On newer boards, the switches will be surface
mount components; on older boards the switches are thru-hole
components.
PRINTED CIRCUIT
BOARD REVISION
"J" or earlier
"K" or later
The U4 receiver PCB layout (34A8507K and earlier) has been
revised due to discontinued status to part number 188A190 (FM IF/Quad
detector). The new replacement component 188A129 (FM IF/Quad
detector) is not pin for pin compatible so, associated support circuitry
was added which results in the new PCB layout (34A8703). Also a new
choice of RF front end filters were chosen which contributed to the new
PCB layout change
PRINTED CIRCUIT
BOARD REVISION
34A8507K or earlier
34A8703
17
VOLUME CONTROL KNOB
46A8048
46A8069
RUBBER ACTUATOR
PART NO.
66A8039
66A8044, 66A8045
FM IF / QUAD
DETECTOR
U303 and U313
U315 and U316
ASSEMBLY PART NO.
90A8652
90A8747
PUSHBUTTON SWITCH
PART NO.
55A187 (thru-hole)
155A03 (SMT)
QUADRATURE
COIL
L304 and L310
FL311 and FL313
25D1062 (AG)