Philips MDV434/55/77 Service Manual page 13

All output voltages on the power board is 0V or deviated.
All output voltages on
the power board is 0V or
deviated
Yes
Check whether
F1 is blown
No
Check whether there is
300V on C4.
Yes
Check whether 100KHz
oscillating signal
Pin6 of U1
Yes
Check if +5V, +3.3v, +12V,
-12V and -24V are short.
Yes
Check whether the components in the
short-circuit voltage are defected or eroded.
4-3
Yes
No
No
on
No
Replace F1
Replace C4 if D1, D2, D3, D4 are
normal.
Check/ replace U1.
U1(PIN 3 - RC waveform)
Check whether U1 are eroded.
Trouble shooting chart
U1(PIN 8 - Drain waveform)