As such boards are cheap and fail quite easily (both the two sustain and
the buffers) Philips service manuals are more oriented at board
swapping then at proper testing. In this particular case the buffer boards fail very easily because of a bad soldering to IC. The short will regularly blow the main sustain board.
To start when a main sustain (e.g. Ysus) is fried the TV will go in protect mode with the led flashing in standby. One test is done disconnecting the Sus board (with power off) and restarting the TV. If TV does not go in protect, then the sustain board was good.
If there is no protection:
The first thing to check on a main sustain board is the fuse. If the fuse has blown the IC is probably fried.I believe fuse is F5004. Check for swollen capacitors that may have blown. Test the FET. That is the core of the board as it is the power amplifier.
Here the service manual:PHILIPS_SM_15540.pdf
- Right Click "Save Target As"Here a more useful service manual.
Check and follow troubleshooting diagrams in manual.
Here some troubleshooting from users.
Note:if buffer board was shorted, then the main sustain board is usually faulty.