50pg20 Power Cycling When Power Applied

[Vladas]

Hi Guys and Gals.. my first post.. Hope I don't mess things up! I have a
LG 50 Inch plasma that when I apply power the standby clicks on and off at the power supply relay, causing the power switch lamp to go from blue to red and back again over and over.. Replaced common caps on board 3300 uf and 680m uf .. still no standby reset. checked for shorts.. 5v, 16v etc seem fine on outputs.. Any suggestions would be greatly appreciated!

[tom66]

Re: 50pg20 Power Cycling When Power Applied

Check Vs/Va on PSU. If you need help, post pictures of the chassis.
Very common issue on the PSU of this LG is a failed power resistor.

[Vladas]

Re: 50pg20 Power Cycling When Power Applied

Thanks Tom, I was hoping to get to you.. I've read some great information from you.. I will see what I can do about the chassis pictures.. This problem was intermittent but know doesn't want to go into standby at all... All Vs/Va seem to be fine (no load).

[Vladas]

Re: 50pg20 Power Cycling When Power Applied

Having a tough time trying to figure out how to post pictures....

[Vladas]

Re: 50pg20 Power Cycling When Power Applied

Exactly like this one on another post:
http://i469.photobucket.com/albums/r...b/DSC01980.jpg

[tom66]

Re: 50pg20 Power Cycling When Power Applied

Use the "Manage Attachments" feature, it's below the post window.

[Vladas]

Re: 50pg20 Power Cycling When Power Applied

Not the best resolution.... Where would this power resistor be located? secondary on power supply?

[tom66]

Re: 50pg20 Power Cycling When Power Applied

Those three white cuboids, top right of PSU.

[Vladas]

Re: 50pg20 Power Cycling When Power Applied

Better one of power supply...

[Vladas]

Re: 50pg20 Power Cycling When Power Applied

Is there a way of verifying the values of these resistors? Simple ohms check?

[tom66]

Re: 50pg20 Power Cycling When Power Applied

Yep, read the value on them & check in circuit.

[Vladas]

Re: 50pg20 Power Cycling When Power Applied

In circuit I'm getting 10.25, 10.07, and 10.47 ohms on these three resistors..

[Vladas]

Re: 50pg20 Power Cycling When Power Applied

I don't think the problem is caused by connection of the Ysus or Zsus boards... Problem occurs when the Finger main input board (AV Inputs board) is connected.. Tried another board with same results.. Could not find short on either of them..

[tom66]

Re: 50pg20 Power Cycling When Power Applied

OK, do you see a point marked EXT AUTO GEN on the control / logic board?
The control board is the board connected to the main board, Y-sus and Z-sus, and it's green.

[Vladas]

Re: 50pg20 Power Cycling When Power Applied

Yes, I jumped this to test the board before replacing the Zsus board.. Was only getting fuzzy snow around screen edges with bad Zsus board (Blotches)... I could see pattern changes around edges at that time..

[tom66]

Re: 50pg20 Power Cycling When Power Applied

With new Z-sus what do you see?

[Vladas]

Re: 50pg20 Power Cycling When Power Applied

Well. it worked for about a week.. great picture , HD , everything.. When I turned unit off with remote it would cycle on and off at the switch (Red/Blue) a couple of times and then go into standby.. Seemed to be ok though... I unplugged the tv once and now it just cycles when I plug it in (no standby)..

[tom66]

Re: 50pg20 Power Cycling When Power Applied

Perhaps your replacement board is faulty...

[Vladas]

Re: 50pg20 Power Cycling When Power Applied

The cycling issue happens whether the zsus or the ysus boards are connected or not.. Really thought it could be in the power supply... Maybe a load issue though... the control chip on the board U701 I believe it is, might be acting flaky .. Also read something about opto couplers on the Ac detect could be an issue... I'm digging...

[Vladas]

Re: 50pg20 Power Cycling When Power Applied

I have two main boards (AV input)... Yesterday I plugged in the second board and the unit went immediately into standby.. As soon as I hit the power switch on the front of the TV it started to cycle again... Now it does it with either main board...