Samsung DP50747 Powers on then off

[pc_doc_al]

Sanyo DP50747
Samsung Panel
Chassis # DP50747-03

TV was DEAD, no relays and no led, so I replaced LJ92-01510A Power Board.
Now, Relays click and LED comes on for 20 seconds then relays click and LED goes off. Same results with Y or X sus disconnected or with both disconnected. I have no voltage on Vs, Va, or Ve. I believe my replacement board maybe bad? What is everybody's thoughts.

Thanks,
Steven

[tom66]

Re: Samsung DP50747 Powers on then off

Try this test:-
https://www.badcaps.net/forum/showpo...61&postcount=2

[pc_doc_al]

Re: Samsung DP50747 Powers on then off

There is no change in results

[tom66]

Re: Samsung DP50747 Powers on then off

OK. Are there any labels next to the connectors going from the power supply board to the main board? The main board is the board with the video connectors on it.

[pc_doc_al]

Re: Samsung DP50747 Powers on then off

Yes they are labeled. I have attached a picture of the connectors.

I just noticed that I Labeled my thread a Samsung DP50747.
It is a Sanyo with a Samsung panel.
Sorry about that.


Steven

[tom66]

Re: Samsung DP50747 Powers on then off

OK, please check PS ON and AC DET while the set powers on and the relays click. All connectors/power board to be installed.

[pc_doc_al]

Re: Samsung DP50747 Powers on then off

PS ON 4.8v with power plugged in and 28.5 mV after relays click

AC DET 5.2v with power plugged in and 5.2v after relays click.

[tom66]

Re: Samsung DP50747 Powers on then off

OK, this indicates a fault with the power board.
Have you checked all the fuses on the power board?

[pc_doc_al]

Re: Samsung DP50747 Powers on then off

Both fuses test good

[pc_doc_al]

Re: Samsung DP50747 Powers on then off

Correction, all three fuses test good

[tom66]

Re: Samsung DP50747 Powers on then off

Any way you can see to check voltage across the 450V large caps as relay clicks in?

[pc_doc_al]

Re: Samsung DP50747 Powers on then off

The 450v caps are at 55.8V then drop to 23.6V when relays click in.

[tom66]

Re: Samsung DP50747 Powers on then off

V DC? 55.8V is not right at all.

[pc_doc_al]

Re: Samsung DP50747 Powers on then off

Sorry I missed the "across" part.

386 V

[tom66]

Re: Samsung DP50747 Powers on then off

That's OK then. The power supply is receiving the signal to turn on, but it is not starting up the main supplies. Check the Vs/Va output for shorted diodes. Also, locate any multi-pin chips near the Vs/Va output on the primary side -- if you find any list their part numbers. Any BN44, BN9x, LJ9x etc numbers on the power supply?

[pc_doc_al]

Re: Samsung DP50747 Powers on then off

Here are the numbers I found.
LJ92-01510A
LJ41-05246A

I see the following:
FDD 8880
LM393
3037cs

I believe all the diodes are good.

[tom66]

Re: Samsung DP50747 Powers on then off

Any visible on the primary side?

[J-Pow]

Re: Samsung DP50747 Powers on then off

So was there ever a solution as to what the cause was? Any help greatly appreciated

Thanks

[pc_doc_al]

Re: Samsung DP50747 Powers on then off

Tom, where did we leave off? I did replace the Main Power board and now I get a green power led that stays on for about 6 seconds then clicks off. The panel still does not light up.

Thanks,
Steven

[pc_doc_al]

Re: Samsung DP50747 Powers on then off

Update!
I rechecked all my cable connections and found one that was not secure. It is working great now.
Thanks Tom66 you have saved me once again.