Philips DVD712 Service Manual page 37

Diagnostic Software Descriptions And Troubleshooting
TROUBLESHOOTING POWER SUPPLY UNIT VFM EURO
START
Check DC voltages
+12V, +5Vstdby, -5V, +5V, +3V3
Disconnect the power supply from the MAIN Board
Connect dummy load resistors 10W ( min 5W ) :
10 ohm at +3V3, 15 ohm at +12V and ground
Check DC voltages
+12V, +5Vstdby, -5V, +5V, +3V3
These voltages will be somewhat higher than specified
Check the +3V3 and +12V
Check +12V path : D6241, C2240, L5240
Check +3V3 path : D6210, C2210, L5210
Connect the mains inlet to a mains isolated variac
Turn input voltage up and check across C2121
the voltage should be
+/-1.41 X Vin AC
Is power supply ticking?
Check supply voltage on pin 7 of IC7145
Vcc within 10V - 16V (typical )
Power Supply Unit
OK
OK
NOK
OK
NOK
OK
NOK
OK
NOK
OK
YES
NO
NOK
OK
DVD712-722
Power Supply
OK
Power Supply OK
Check : Mono Board
A/V Mux Board
Display Board
Check the path of the faulty voltages:
+5V path: D6230, L5231, T7235, C2230, C2238, C2239
-5V path: D6250, C2250, L5222, T7257 and T7255
regulator unit
+5V_stby path: R3233, D6233
Check standby control at pin 10 of conn. 0205
Standby ON: 5.0V +/- 0.5V
Standby OFF: 0V
Check the functionality of the following components:
F1120, L5120, D6118, D6119, D6120, D6121, C2121
Check the load on the secondary output
Check overvoltage protection:
D6141, R3139, T7141, T7150, R3150
Check oscillator voltage on pin 4 of IC7145
Check R3146,C2157 and replace IC7145
Check drive circuit : gate voltage of Mosfet 7125,
components R3111, R3140, R3156,R3125,D6140
Check working of regulation circuit :
T7131,T7201,R3201,R3202,R3204,R3205,
R3206,R3207,R3208,R3153,R3154,R3262,C2202
Check start-up circuit and Vcc supply circuitry
Replace IC7145
5. GB 37
CL16532007_075.eps
200401