TNPA4250 Board Repair

[canadaboy25]

Re: TNPA4250 Board Repair

I would try testing VAD, VSCN and VSET - they can cause 7 blinks error.

I'm sorry but I have no idea what those are haha

I'm kinda a noob at plasma's

[tom66]

Re: TNPA4250 Board Repair

They are voltages marked on the SC board. If in doubt refer to the service manual.

[canadaboy25]

Re: TNPA4250 Board Repair

Well I connected the power cable to the SC board and left the data plug disconnected so the tv would stay on.

The VAD tested fine
The VSCN only had 9.3 volts
The VSET tested 321 and is supposed to test 365 +or- 7 volts

I used chassis as ground reference.

[canadaboy25]

Re: TNPA4250 Board Repair

Any ideas?

[tom66]

Re: TNPA4250 Board Repair

If VSCN tests bad with the SU/SD unplugged you probably have a short on the SC board, double check you replaced all shorted FETs.

[canadaboy25]

Re: TNPA4250 Board Repair

I tried disconnecting the SU and SD boards from The SC board and the VSCN voltage is still only 9 volts.

I tested all of the MOSFET's again and they all tested fine.

All of the tests were done with the data cable unplugged from the SC board so that the TV would stay on.

[tom66]

Re: TNPA4250 Board Repair

You may require that cable in to get VSCN, it will be briefly available if there is no fault with it so try that.

[canadaboy25]

Re: TNPA4250 Board Repair

With that cable connected the VSCN voltage jumps to 30 volts and climbs to 35 volts but then the TV shuts off.

The voltage in the manual is much higher than this or does it just need time to climb up?

[tom66]

Re: TNPA4250 Board Repair

It should be around 140V so that is bad.

[canadaboy25]

Re: TNPA4250 Board Repair

Well of it's not a a shorted transistor what else could it be?

[tom66]

Re: TNPA4250 Board Repair

Bad VSCN generator circuit, leaky transistor, bad diode are possibilities.

[canadaboy25]

Re: TNPA4250 Board Repair

Well I recently picked up an oscilloscope and a desoldering station so those should make troubleshooting go a lot quicker.

I have a lot of time to work on this so if you could tell me anything that I should test I would greatly appreciate the help!

[tom66]

Re: TNPA4250 Board Repair

What oscilloscope did you get? That would be very helpful.

[canadaboy25]

Re: TNPA4250 Board Repair

What oscilloscope did you get? That would be very helpful.

I have the Rigol DS2072A.

[tom66]

Re: TNPA4250 Board Repair

Nice choice! Very powerful scope!

Connect your oscilloscope to the SC output. If you need help locating where, post a clear picture of it.

[canadaboy25]

Re: TNPA4250 Board Repair

Would you like a picture of the SC board?

[tom66]

Re: TNPA4250 Board Repair

That would help yes.

[canadaboy25]

Re: TNPA4250 Board Repair

I apologise in advance for the poor picture quality.

This is such a large board and I don't have a very good camera or lighting.

If you need close-ups of specific areas just let me know.

[tom66]

Re: TNPA4250 Board Repair

Can you see a point marked TPSC1?

[canadaboy25]

Re: TNPA4250 Board Repair

I found that test point.

Am I supposed to scope that output with the TV turned on? If so should i have the main power connector and the data connector coming from the main board connected? If i have the data cable connected then the TV shuts off in a matter of seconds. Will that be long enough to perform a measurement?