Shure UC1L Service Manual page 23

Bench Checks
25A1043 (RI)
Dc Problems
Make all dc measurements with respect to the rf ground,
unless otherwise specified.
Verify that the battery voltage is between 6.0 Vdc and 9.5 Vdc.
Check for +5 Vdc at labeled test points on the audio and rf
boards.
If incorrect voltage is present, check the biasing resistors' values.
Trace the dc back to the battery and check the power switch.
Look for open coils, cracked parts, reversed polarity capacitors,
and solder shorts.
If there is a short to ground from 5 Vdc, try to isolate different
parts of the circuit.
Verify that the rf
and power down to 0 Vdc during normal operation. Trace the
signal to the microprocessor. Q101 should be saturated during
normal operation.
Verify that the battery voltage appears at U205, pin 6,
(TP +9 Vdc).
Rf Frequency Problems
If the carrier is out of specification by less than 40 kHz and can-
not be corrected by adjusting C123, check the values of C123,
C124, and Y101. If these values are correct, replace Y101. As
a last resort, replace the synthesizer, U104.
If the carrier frequency is not 782 and 810 MHz, or is unstable,
the loop is unlocked:
Check solder connections at the VCO, microprocessor (traces
LE, D, and CK) and synthesizer, U104.
Check for 4 MHz oscillation at U104, pins 1 and 2. If there is not
4 MHz oscillation, replace the crystal, Y104.
Check the values and polarity of the loop filter: R121, R122,
R123, C129, C130, C131, and C132. Check the bias voltage of
U104, pins 3 and 4; and U106, pin 8. As a last resort, replace
the synthesizer, U104.
The tuning voltage of the VCO at U104, pin 5, should be approxi-
mately 3 Vdc when the transmitter is programmed for 800 MHz
operation.
23
Shure UC1 Body-Pack UHF Transmitter
signal changes from +5 Vdc at power up
OFF
Bench Checks