Shure U4D Service Manual page 27

Noise Set-Up (Channel A)
RF SIGNAL GENERATOR
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
DC BLOCK
ANTENNA A IN
S201
(OFF)
C242
C227
P202
P203
J302
Figure 10. Channel A 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. Use amplitude increments of 10 to 100 mV.
2. Verify that the rf signal generator power is –61 dBm.
3. Place the (+) terminal of a dc voltmeter on the (+) side of C227
and connect the (–) terminal to ground.
4. For 34A8507F or earlier PCB versions, adjust R337 (not shown
above) until the voltmeter reads 8.00 ± 0.03 Vdc. For 34A8507G
or later PCB versions and PCB 34A8703, adjust R264 to 4.00 ±
0.03 Vdc.
26
NOTE: DC VOLTAGES ARE PRESENT
AT MOST RF TEST POINTS. USE A DC
BLOCK ON THE RF SIGNAL GENERATOR
TO PROTECT TEST EQUIPMENT.
ANTENNA B IN
S201
(OFF)
R264
P202
P202
P203
Service Procedures
P202