LG55LS4500 picture went bye bye

[Tim K]

Re: LG55LS4500 picture went bye bye

1) Check the reistance between VGH and Ground to see what you get.
2) Disconnect the cables between T-CON and the LCD panel and see what VGH will be.
BTW, VGL is the LCD minus power supply so it should show as minus reading on your meter, I.E. -6.85V.
Here is some info about LCD Bias power supply function:

Sorry, I didn't even notice, but YES both VGL and VGH were actually negative values.
VGL: -6.85
VGH: - 0.77

VGH resistance to ground is 1.52
With both cables disconnected resistance was the same.

[budm]

Re: LG55LS4500 picture went bye bye

Sorry, I didn't even notice, but YES both VGL and VGH were actually negative values.
VGL: -6.85
VGH: - 0.77

VGH resistance to ground is 1.52
With both cables disconnected resistance was the same.

1.52 Ohms? Start check the caps connected to that VGH pad, you have shorts some where.
I see caps C182, 183 which are filter caps for the VGH, so remove them to see if the shorts go away or not.
https://www.badcaps.net/forum/attach...2&d=1564087548

[Tim K]

Re: LG55LS4500 picture went bye bye

1.52 Ohms? Start check the caps connected to that VGH pad, you have shorts some where.
I see caps C182, 183 which are filter caps for the VGH, so remove them to see if the shorts go away or not.
https://www.badcaps.net/forum/attach...2&d=1564087548

When you say "remove them" what do you mean?

[budm]

Re: LG55LS4500 picture went bye bye

Unsolder the caps.

[Tim K]

Re: LG55LS4500 picture went bye bye

Unsolder the caps.

How confident are you that the problem lies somewhere on the T-con board? At some point I may just want to replace it for $20 rather than start unsoldering things I can barely see.

[budm]

Re: LG55LS4500 picture went bye bye

Well, that 1.52 Ohm reading on VGH without LCD panel connected is definitely not right.

[Tim K]

Re: LG55LS4500 picture went bye bye

Well, that 1.52 Ohm reading on VGH without LCD panel connected is definitely not right.

At this point I don't mind spending $20 on a new T-con if that's the cause. I'd just hate to do it and that not fix things. Is there any way to rule out there being a problem on the other boards?

[nomoresonys]

Re: LG55LS4500 picture went bye bye

Well did you check the caps for shorts ala post 22??

[budm]

Re: LG55LS4500 picture went bye bye

At this point I don't mind spending $20 on a new T-con if that's the cause. I'd just hate to do it and that not fix things. Is there any way to rule out there being a problem on the other boards?

So you are willing to spend $20 on KNOWN GOOD WORKING T-CON (make sure to match the bar coed sticker numbers not the white silkscreen printing on the board) on 55 inch TV, then just do it.
I gave free guide troubleshooting steps by step to get to this point at no charge which is worth a lot more than $20.
We know that the backlights is working and the main board is sending the command signal to turn on the power supply and the backlights circuits, that is all we know at this point.

[Tim K]

Re: LG55LS4500 picture went bye bye

So you are willing to spend $20 on KNOWN GOOD WORKING T-CON (make sure to match the bar coed sticker numbers not the white silkscreen printing on the board) on 55 inch TV, then just do it.
I gave free guide troubleshooting steps by step to get to this point at no charge which is worth a lot more than $20.
We know that the backlights is working and the main board is sending the command signal to turn on the power supply and the backlights circuits, that is all we know at this point.

It's not that I don't appreciate the help, or that $20 is nothing....it's just I don't think I can proceed any further. I was able to remove and replace a ceramic disc capacitor last year without any problem, but I don't have the precision tools or the dexterity to unsolder 2 tiny caps. Even if I managed to remove them without damaging the board, I don't think I would ever be able to solder them back in place.

[nomoresonys]

Re: LG55LS4500 picture went bye bye

Ok, test the caps on the board, see if they read shorted.