Shure U4D Service Manual page 31

Noise Setup (Channel B)
NOTE: DC VOLTAGES ARE PRESENT
AT MOST RF TEST POINTS. USE A DC
BLOCK ON THE RF SIGNAL GENERATOR
TO PROTECT TEST EQUIPMENT.
ANTENNA A IN
S201
(OFF)
P203
J302
25D1062 (AG)
Shure U4D Dual Diversity UHF Receiver
The Noise Setup procedure aligns each Channel so that for a given
signal-to-noise ratio, the respective dc levels match.
DC VOLTMETER
U202
C242
R265
C239
U203 U211
P202 P202
Figure 14. Channel B, Noise Setup Connections
1. Set the modulating frequency from the audio analyzer to 60 kHz
and, if necessary, readjust the amplitude so HI EXT and LO EXT
lights turn off.
2. Verify that the rf signal generator output power is –61 dBm.
3. Place the (+) terminal of a dc voltmeter on the (+) side of C242
and connect the (–) terminal to ground.
4. For 34A8507F or earlier PCB versions, adjust R389 (not shown
above) until the voltmeter reads 8.00 ± 0.03 Vdc. For 34A8507G
or later PCB versions and PCB 34A8703, adjust R265 to 4.00 ±
0.03 Vdc.
30
RF SIGNAL GENERATOR
ANTENNA B IN
S201
(OFF)
P203 P202
Service Procedures
DC BLOCK
P202