WARNING: DISCONNECT POWER PRIOR TO SERVICING
2-9
TABLE 2-1. EXCITER CIRCUIT BOARD TROUBLESHOOTING
(Sheet 3 of 3)
SYMPTOM
CIRCUITRY TO CHECK
LOW DEMODULATOR LEFT
1. Defective U2A, U2B, U1A, U1B, U3A, U3B or
CHANNEL MODULATION LEVEL
P2 programming.
WITH LOW EXCITER
MONITOR LEFT CHANNEL
MODULATION LEVEL
LOW DEMODULATOR RIGHT
1. Defective U5A, U5B, U4A, U4B, U6A, U6B or
CHANNEL MODULATION LEVEL
P3 programming.
WITH LOW EXCITER
MONITOR RIGHT CHANNEL
MODULATION LEVEL
TABLE 2-2. STEREO CIRCUIT BOARD TROUBLESHOOTING
(Sheet 1 of 2)
SYMPTOM
CIRCUITRY TO CHECK
RED EXCITER INDICATOR
1. Insert a 1 kHz audio signal at +10 dBm into the left
ILLUMINATED ON
channel and operate the stereo circuit board to stereo.
TRANSMITTER MONITOR
Check for a 3.0V p-p quadrature AM signal at TP-7.
A. If the signal is present, defective U40A, U40B,
T1, U39A, U39B, or U39C.
B. If the signal is not present, check for a
quadrature AM signal at U38 pin 3.
1. If the signal is present, defective U38A, U38B,
U38C, U38D, U38E, Q1, or Q2.
2. If the signal is not present, check for a
quadrature AM signal at U37 pin 1.
a. If the signal is present, defective U37, L4,
L5, L6, L7, D3, D4, or the S2, S3, or S4
programming.
b. If the signal is not present, defective U36,
U35A, U35B, U34A, U34B, U33, U32, or
U26.
NO L-R MODULATION PRESENT
1. Defective U25B, U27B or U31B.
AT THE EXCITER MONITOR
METER