LG 50PC1 -where is 5v standby derived from?

[Cornboats]

Ac only connected. line fuse ok. No red led when ac is switched on.
Set is dead with no 5v standby voltage on ac-d pin of connector P800 on YPSU-J012B board. I've tried to trace origin of this back but got lost on the circuit board. Does anybody know where this voltage is derived from? If you haven't worked on this model other models may be similar so I'd welcome any thoughts and advice.

[ReeceyBurger123]

Re: LG 50PC1 -where is 5v standby derived from?

Have you checked the bridge rectifier and if any voltage is getting past the main filter caps ? ?

[CapLeaker]

Re: LG 50PC1 -where is 5v standby derived from?

Any pics, PS board numbers etc?

[Cornboats]

Re: LG 50PC1 -where is 5v standby derived from?

Hi.
I pulled both bridge rectifiers and diode tested as ok. I've got voltage at main cap.
This board has got a bit of history. Originally came faulty as blowing main fuse caused by shorted fets. I changed these and set powered up and ran for 5 minutes. Then shut down and went into standby. I couldn't find fault so removed previously changed fets and tested again along with components mounted on heat exchangers.
Fitted back together and tested with lamps. Came on and powered up once then shut down. Now dead as a dodo.

[tom66]

Re: LG 50PC1 -where is 5v standby derived from?

You need to supply better photos - it is impossible to see the design properly without them.

[Cornboats]

Re: LG 50PC1 -where is 5v standby derived from?

Board number is YPSU-JO12B-rev1.1. Here's another 6 photos with improved clarity. Some of the photos show components including fets and capacitors removed but all components have since been refitted.

[CapLeaker]

Re: LG 50PC1 -where is 5v standby derived from?

Sorry... there is nothing much I can do with those pics... if you can't read anything on it, I can't either.

Well.. I guess you beat me posting now. :-)

[CapLeaker]

Re: LG 50PC1 -where is 5v standby derived from?

Here is a service manual for your TV.

[Cornboats]

Re: LG 50PC1 -where is 5v standby derived from?

Thanks for the manual- I already have one -doesn't go into much detail regarding psu.
If I could find out what makes the 5v I might stand a chance!

[CapLeaker]

Re: LG 50PC1 -where is 5v standby derived from?

Is there a chance to get better hi res pics of both sides of the board? These pics are pretty dang small to be able to trace anything at all.

[budm]

Re: LG 50PC1 -where is 5v standby derived from?

Good picture at SJ http://www.shopjimmy.com/lg-67099000...wer-supply.htm

[budm]

Re: LG 50PC1 -where is 5v standby derived from?

Transformer T501 (the smallest yellow transformer) in that section is the STBY power supply. But we do need better pictures of YOUR BOARD both top and bottom side so we can see if there are any damaged parts, bad solder joints on the board.
http://www.shopjimmy.com/lg-67099000...wer-supply.htm

[Cornboats]

Re: LG 50PC1 -where is 5v standby derived from?

Many thanks I'll see if there's any voltage there and get back. I've got some high resolution pics but badcaps couldn't upload. I'll try again later.

[tom66]

Re: LG 50PC1 -where is 5v standby derived from?

Needs to be smaller than 2000x2000, alternatively use a service like imgur to upload them and link them here.

[Cornboats]

Re: LG 50PC1 -where is 5v standby derived from?

Standby voltage is back but--
I traced AC-D pin on P800 connector back to microcontroller U701. The feed for this controller comes from optocoupler PC201. With the board on the bench I turned board on to try get some voltages and the relays clicked in and then off. I refitted to the tv but I'm now back to where I was before I lost the 5v standby. Power on but with connectors connected or disconnected the result is the same. Relays cut in and then off. The shutdown through the speakers is not unlike a fuse blowing!
Theres obviously a short but I can't find it!
In the few seconds set is on the set voltages are VS 196, Va 60 -as per label.
Heres another 4 pics with higher resolution. Site won't accept any higher I'm afraid.

[necatduman]

Re: LG 50PC1 -where is 5v standby derived from?

By the end of the block is 300volt stanbay kondanstötr in LA I stanbay +5 volts çıkışdiyot + 5Volt scarce lessons recharge circuit voltage Amedaki interests amahiç whether a socket attached

[Cornboats]

Re: LG 50PC1 -where is 5v standby derived from?

Thanks for your interest in replying, I don't understand but I will try and get translated.

[Cornboats]

Re: LG 50PC1 -where is 5v standby derived from?

This is all I could find by translating;
"By the end of the block is 300v standby capacitor in LA1 standby+5V diode"
I'm afraid its not enough to help but thanks anyway.

[tom66]

Re: LG 50PC1 -where is 5v standby derived from?

Have you tried disabling AC-det optocouplers?

[CapLeaker]

Re: LG 50PC1 -where is 5v standby derived from?

Is the 5v line on the main board shorted? So when you plug the main board in, it shorts the 5v rail on the power supply?