TNPA4250 Board Repair

[canadaboy25]

Re: TNPA4250 Board Repair

Any ideas?

[canadaboy25]

Re: TNPA4250 Board Repair

Bump

[tom66]

Re: TNPA4250 Board Repair

Do both LEDs go off at about the same time?

[canadaboy25]

Re: TNPA4250 Board Repair

Yes, they both slowly dim and go out at the same time.

[tom66]

Re: TNPA4250 Board Repair

Tricky one. Not obvious, I'm afraid. Are the 15V and 15V_F good? (15V_F may need to be measured to -Vad or to the SUS output)

[canadaboy25]

Re: TNPA4250 Board Repair

Well I found TP15v on the SC board and there was about 15.7 volts at that point before the TV shuts down so I assume that's good.

However, I couldn't find the 15V_F test point anywhere. I used Adobe and searched through the service manual for 15v_F but nothing came up. What am I supposed to test for the 15v_F?

[canadaboy25]

Re: TNPA4250 Board Repair

Well I found this manual on your website and it has a bit more detail on the blink codes.

Should I go to the trouble of finding these pins and try and set them low or is this not likely to be the problem?

[tom66]

Re: TNPA4250 Board Repair

Yes, it's probably worth checking that - interesting, not seen that before.

[hennes]

Re: TNPA4250 Board Repair

Hi,
have the same model,
and by using manual from E-tanya and this threat found one of the 5N... mosfets was short.

Replaced it by a IRFP 4229.

For that measuring,i just opened the drain connection of each mosfet from the shortened cluster carefully and made diode-test.

The bad one only had 8mV between S and D.

The other parts of that group vary about up to 4mV.
Maybe that's reason that some of them die....

I was lucky to check and repair this with all boards on place.

good luck..

[canadaboy25]

Re: TNPA4250 Board Repair

Sorry for the slow reply, I had to RMA my soldering iron.

Anyways, I soldered a wire onto pin 90 of the IC mentioned in the guide attached below and it turns out that pin was being set high which would mean an error. So I shorted that pin to ground and turned on the TV. The TV stayed on but there was an irregular hum coming from the SC board.

I have attached an rar file with the sound mp3 file inside it. You will probably have to turn your speakers way up to hear it but it sounds like a quick chirp and progresses to a steady hum and at that point I take the wire off ground so the TV will shut down because I'm worried it's going to blow up.

Any advice?

[tom66]

Re: TNPA4250 Board Repair

So, you have good picture in this mode?

[canadaboy25]

Re: TNPA4250 Board Repair

If by picture you mean image on the screen, then no there is nothing on the display.

[tom66]

Re: TNPA4250 Board Repair

I don't have any good suggestions right now, I'm afraid.

[canadaboy25]

Re: TNPA4250 Board Repair

Is there any way we can trace the shutdown signal and see what is causing it?

[tom66]

Re: TNPA4250 Board Repair

You could try tw's suggestion previously regarding tracing diodes leading to SOS7 signals.

[hennes]

Re: TNPA4250 Board Repair

check the driver of the replaced mosfet.

In the repair kid you can buy on ebay there are some smd resistors etc. included.
So that may be worth to check .If TV runs you can use your Oszi for G signal and make a cross check....

I would come from this side to the problem. But don't run your TV to long with your ''pass by'' circuit....

[hennes]

Re: TNPA4250 Board Repair

Anyway,I'd found some data. 2n2307 is simlar to stp9nk50z....

[canadaboy25]

Re: TNPA4250 Board Repair

The other thing is maybe find the diodes these signals pass through for each section they monitor and find the one which has a high on the anode side since all the cathodes are tied. may be able to at least find the section producing the high for shutdown and trace it??

How would I find these?

[tw2005]

Re: TNPA4250 Board Repair

open the manual and look at the sos7 ccts.

looks like, Vscn,Vset, Vad, 16V, 5v_f1, 5v_v2 (5v for the sd/su boards) are all part of the error detection.

Also looks like these had issues with panels and firmware

[canadaboy25]

Re: TNPA4250 Board Repair

open the manual and look at the sos7 ccts.

looks like, Vscn,Vset, Vad, 16V, 5v_f1, 5v_v2 (5v for the sd/su boards) are all part of the error detection.

Also looks like these had issues with panels and firmware

Well I tested all of the voltages and diodes that were circled in red in the second image you attached and everything tested fine.

I'm trying to figure out where the S0S6 is coming from. I attached a picture of the S0S6 block. I removed the diode circled in red so that the signal would not make it to the D board and the TV will keep running. The input line with the green led has 55.5 volts on it while the TV is running. The 5 and 15 volt sources in the image I attached are both fine so it must be getting the error from the 55.5 volt input. Does anyone know what this is supposed to be?

I also attached the page of the manual with the S0S6 block on it.