Shure U4D Service Manual page 30

THD Verification and RSSI Adjustment (Channel B)
DC VOLTMETER
AUDIO ANALYZER
Service Procedures
Shure U4D Dual Diversity UHF Receiver
ANTENNA A IN
S201
(OFF)
P202
P203
TP308
U310
L304 for PCB
34A8507
FL313 for PCB
34A8703
J302
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.
29
RF SIGNAL GENERATOR
S201
(OFF)
P202
P203
R367
TP325
NOTE: DC VOLTAGES ARE PRESENT
AT MOST RF TEST POINTS. USE A DC
BLOCK ON THE RF SIGNAL GENERATOR
TO PROTECT TEST EQUIPMENT.
DC BLOCK
ANTENNA B IN
P202
P202
25D1062 (AG)