WARNING: DISCONNECT POWER PRIOR TO SERVICING
2-10
TABLE 2-2. STEREO CIRCUIT BOARD TROUBLESHOOTING
(Sheet 2 of 2)
SYMPTOM
CIRCUITRY TO CHECK
LOW DEMODULATOR LEFT
1. Insert a +10 dBm 1 kHz signal into the left channel.
CHANNEL MODULATION LEVEL
Check for a 2V p-p 1 kHz signal at U4 pin 1.
WITH NORMAL EXCITER
A. If the signal is present, defective U4B, U5A, U5B,
MONITOR LEFT CHANNEL
or J1.
MODULATION LEVEL
B. If the signal is not present, defective U1A, U2,
U1B, U3, or U4A .
LOW DEMODULATOR RIGHT
1. Insert a +10 dBm 1 kHz signal into the right
CHANNEL MODULATION LEVEL
channel. Check for a 2V p-p 1 kHz signal at U10
WITH NORMAL EXCITER
pin 1.
MONITOR RIGHT CHANNEL
A. If the signal is present, defective U10B, U11A,
MODULATION LEVEL
U11B, or J2.
B. If the signal is not present, defective U7A, U8,
U7B, U9, or U10A.
TABLE 2-3. CONTROLLER CIRCUIT BOARD TROUBLESHOOTING
(Sheet 1 of 2)
SYMPTOM
CIRCUITRY TO CHECK
NO POWER CONTROL PWM
1. Check for a 1 kHz 15V p-p square-wave
SIGNAL
signal at TP-7.
A. If the square-wave signal is present,
defective Q22.
B. If the square-wave signal is not present,
check for a 1 kHz 50% duty-cycle
square-wave signal at TP8.
1. If the square-wave signal is not present,
defective U44B, U40C, or U46E.
C. If the square-wave signal is not present,
check for a dc voltage proportional to power at
TP11.
1. If the dc voltage is present, defective U44A,
U40B, U41A, U42, or U43.
2. If the dc voltage is not present, contact the
Broadcast Electronics Customer Service
Department.
2. Check for a HIGH at U36C pin 8.
A. If the HIGH is present, defective U36C.
B. If the HIGH is not present, contact the
Broadcast Electronics Customer Service
Department.