Shure U4D - Noise Set-Up (Channel A)

Shure U4D Dual Diversity UHF Receiver
26
25D1062 (AG)
Service Procedures
Noise Set-Up (Channel A)
The Noise Setup procedure aligns each channel so that for a given
signal-to-noise ratio, the respective dc levels match.
P202
P203
C227
R264
C242
P202
S201
ANTENNA A IN
ANTENNA B IN
DC VOLTMETER
RF SIGNAL GENERATOR
P202P202
P203
S201
DC BLOCK
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
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.