Shure U4D, Service Manual

Page: 30 / 47

Shure U4D Dual Diversity UHF Receiver
29 25D1062 (AG)
Service Procedures
THD Verification and RSSI Adjustment (Channel B)
TP308
R367
U310
P202
P203
P202
S201
ANTENNA A IN ANTENNA B IN
AUDIO ANALYZER
DC VOLTMETER
P202 P202
P203
S201
RF SIGNAL GENERATOR
DC BLOCK
TP325
NOTE: DC VOLTAGES ARE PRESENT
AT MOST RF TEST POINTS. USE A DC
BLOCK ON THE RF SIGNAL GENERATOR
TO PROTECT TEST EQUIPMENT.
(OFF)
(OFF)
J302
L304 for PCB
34A8507
FL313 for PCB
34A8703
Figure 13. Channel B RSSI Alignment Connections
1. Change the rf signal generator level to –50 dBm.
2. Measure the total harmonic distortion (THD) at TP308
(U310 pin 7) should be less than 0.5%. If not adjust L304 for
PCB version 34A8507 or adjust FL313 for PCB version 34A8703
to minimize the distortion.
3. Adjust R367 for Vrssi at the wiper (TP325). The Vrssi should be
2.75
±
0.1 Vdc for 34A8507F and earlier PCB versions.The Vrssi
should be 2.3
±
0.1 Vdc for 34A8507G and later versions of the
board and the 34A8703 PCB version.