PN58B550T2F - No power - BN44-0280a

[mark_]

Hello

I have a BN44-0280a power supply that is giving 0 on all DC outputs (Vs/Ve/STDY/+5/+15).
Would anyone have a schematic for power supply?
Or even a couple test points I could narrow down?


Info on board:
Had a blown FS801S QS801 and QS802 were bad and replaced.
Still nothing on outputs.



thanks
MT

[ReeceyBurger123]

Re: PN58B550T2F - No power - BN44-0280a

Are you getting Dc voltage across the main filter caps ?

[mark_]

Re: PN58B550T2F - No power - BN44-0280a

Are those the 3 large caps just before qs801 and 802?

[ReeceyBurger123]

Re: PN58B550T2F - No power - BN44-0280a

Yes

[mark_]

Re: PN58B550T2F - No power - BN44-0280a

Thanks for the replies ..

0 volts on the filter caps ,

I'm not even getting 120 to the ~ ~ pins on either bridge rectifier.
I am getting 120 past both fuses

There are 2 relays and I measure 120AC exiting RL801S and entering RL802S 0 exiting. Going to see if I can find one.

[budm]

Re: PN58B550T2F - No power - BN44-0280a

https://www.badcaps.net/forum/showth...ht=BN44-00280A

To force on the power supply (board is not connected to the main board)
PS-ON = GND
VS-ON = HIGH using 1K resistor between VS-ON pin and the STBY POWER SUPPLY PIN.
Pictures provided by shopjimmy.

[mark_]

Re: PN58B550T2F - No power - BN44-0280a

Thanks for the PS-ON hint.

That gave me my +5 and +15 ... that's as far as I got.
I put the board back in the TV with the X and Y power disconnected but the logic and main boards connected.
Plugged it in and the fuse blew.
Going to check tomorrow if the MOSFETs are still good ...

Thanks for the help
mark

[mark_]

Re: PN58B550T2F - No power - BN44-0280a

Found another fuse ,

I still have my +5 and +15
as soon as I put VS_ON to high the fuse goes.

[dick_barton]

Re: PN58B550T2F - No power - BN44-0280a

With the power off, disconnect all your boards and check for a short circuit or very low resistance to chassis from all the VS points you can find on the boards. You probably have a short circuit on one or more of your boards.

[mark_]

Re: PN58B550T2F - No power - BN44-0280a

with everything disconnected , i short PS_ON to GND I get +5 and +15.
As soon as I put VS_ON high the fuse blows.
DS812 - another bridge (D4SBL20U2290) is measuring a short across the AC ~~ terminals.
Trying to back trace it , schematics would be so nice.

[dick_barton]

Re: PN58B550T2F - No power - BN44-0280a

Have you lifted out DS812 to ensure the bridge rec itself is not short circuited?