2-4
WARNING: DISCONNECT POWER PRIOR TO SERVICING
TABLE 2-1. POWER SUPPLY MODULE TROUBLESHOOTING
(Sheet 2 of 2)
SYMPTOM
CIRCUITRY TO CHECK
RED POWER SUPPLY
2. Place the negative lead on the drain
INDICATION (CONT'D)
and the positive lead on the source and
determine if a short circuit condition is
present.
3. If a short circuit condition is present,
defective Q23.
3. Visually inspect crowbar resistor R72.
4. Check SCRs D13/D14 and diodes D15, D16, and D17
for a short circuit condition.
5. Replace all blown fuses on the circuit board.
NO 120 Hz SIGNAL OUTPUT
1. Check for a 120 Hz square-wave pulse at the
source of transistor Q55 on the controller circuit
board.
A. If a 120 Hz signal is present, defective Q55 on
the controller circuit board.
B. If a 120 Hz signal is not present, defective U3
on the power supply circuit board.
2. Re-install the power supply circuit board and
operate the transmitter. If the circuit board
remains defective, contact the Broadcast
Electronics Customer Service Department.
MOD PWR INDICATORS
1. Check U7, U9A, U9B, U9C, U9D, Q9 and Q21.
EXTINGUISHED ON A
POWER BLOCK
2-18.
COMPONENT REPLACEMENT PROCEDURE.
Component replacement procedures for
the power supply circuit board are presented in PART I SECTION V. Refer to
COMPONENT REPLACEMENT in SECTION V as required for the replacement
procedures.