LG display sporadic screen issues

[Clydeuk]

Re: LG display sporadic screen issues

Just as a matter of interest have you checked the LVDS cable from main board to T-CON? Could be an intermittent connection or break, I've even had a tarnished connection cause this fault, which can take any length of time between appearances making fault tracing very difficult. If there's a poor timing signal getting the the T-CON it will confuse it, after all it's only a processor working on data.

In my case the problem was the actual LVDS socket on the T-CON, but you've ruled that out with board replacement. Cable itself is a possibility though.

[thedosmann]

Re: LG display sporadic screen issues

There is a board in between the mainboard and t-con, I think it is an FRC board I managed a tight pic of it below. It looks like the t-con went out again since it is getting 12+/- at both ends of F1(curious as to why t-con went out again. I'm thinking I should get another t-con and also the FRC board? Presently there is no picture but back light is on and T-con is getting the juice so am I correct to follow this path? That is if I can find another T-con and also the FRC board.
The t-con part# is68700-0402c the chip is lg5822
The FRc looks to be mst6m30 v1.0 -c
Could the FRC board been causing these issues all along?

[tom66]

Re: LG display sporadic screen issues

Are you sure those input LVDS connectors and output on the FRC board are properly lined up?

[thedosmann]

Re: LG display sporadic screen issues

I double checked that. I took a pic before I detached everything and it showed the original alignment. Do you see something off?

[tom66]

Re: LG display sporadic screen issues

I'm noticing the bent pins and I'm not sure I like that... Check none are shorting against each other.

[thedosmann]

Re: LG display sporadic screen issues

K..will do. The pic your looking at is right after I loosened board and turned over to view. I'm not at the unit right now but enlarging pic doesn't show them touching. I think this was build indicator on where to plug in?

[thedosmann]

Re: LG display sporadic screen issues

Finally got back to this. I put the old t-con back in to check if that is what went out. I expected to see the same behavior that made me replace it. Instead it looks like the original issue, but can't be sure. Right now it's working with no issues. Couple of questions:
Does the orientation of the panel ( IE: upside down, flat, laying face down, ...) affect normal operation of the panel?
Are Gremlins real?

At this point I can only wait to see if it messes up. If it does I'm thinking I got a bad t-con from ebay and I'll need to order another one. I hope its not the frc board as I haven't found another one.

[tom66]

Re: LG display sporadic screen issues

No, and maybe.

[thedosmann]

Re: LG display sporadic screen issues

Well it started messing up again. It will go into a period of sporadic screen distortions and then straighten out and stay that way until it starts messing up again. It could stay ok for a while before it starts messing up again. Sometimes it will be distorted on a power up sometimes not but it will eventually show a good screen.. until it starts messing up again. I've done tap tests at several locations with no effect. T-con board?

[tom66]

Re: LG display sporadic screen issues

Have you tried using heat to test?

[thedosmann]

Re: LG display sporadic screen issues

No, but I guess I can get the hair dryer out and start aiming it at different locations and see what happens. I'll let you know.

[thedosmann]

Re: LG display sporadic screen issues

Using a hair dryer at various locations in back did not have any effect. The unit stayed up and running until today, so pretty much 2 days, when the screen messed up. Would it be a total waste of money to try another t-con board?

[tom66]

Re: LG display sporadic screen issues

You can try swapping the board. However, I would advise you wait for the problem to reoccur before diagnosing further. Freeze spray may also help -- cooling may have a greater effect. An upside down compressed air can works good as freeze spray.

[thedosmann]

Re: LG display sporadic screen issues

What areas should I concentrate on, power, inverter, frc, t-con, mainboard? Also the frc is tight underneath and hard to get to so it would be hard to get to it with a shot cold air, I will try.

[tom66]

Re: LG display sporadic screen issues

I would try FRC, T-con and main, in that order.

[thedosmann]

Re: LG display sporadic screen issues

k

[thedosmann]

Re: LG display sporadic screen issues

update:
I searched for the FRC board for several months; hoping one would come available, with no success. I finally decided to order one that had the same IC part number, knowing this was a stab in the dark. After receiving the board and placing it in the unit I found myself back at square one as the replacement board didn't work. I went ninja on the old FRC board to see if I could visually find what was wrong with the board. I had looked at it several times before to no avail. I hadn't found any broken or burnt traces, no fat capacitors, and no obvious problems with any of the board components. This time I got out my meter and started testing current flow and resistance but with the board out of the unit this was just an effort in futility as far as discovering any malfunctioning component on the board. Just as I was about to resign myself to not being able to fix the unit I got out my magnifier and gave the board one last look. I noticed the top of one of the capacitors looked off so I zeroed in on it and discovered a tiny hole at the top. The hole was smaller than a pin head. I actually got a pin and tried to push it in the hole and the pin was too big. I extracted the part and soldered another capacitor in place of like volt and capacitance values and placed the board back in unit. I turned the unit on and the problem was gone. After 5 days, of leaving the unit on, the display issues never returned.

Note: The pic a few posts back show the cap, it is in the far left and back of board in photo.

[tom66]

Re: LG display sporadic screen issues

Glad to hear! Nice simple fix in the end... if only very hard to find...!

[Maxstang]

Re: LG display sporadic screen issues

Post pic of the cap in question! I've also had a failing FRC board exhibit similar symptoms.

[selldoor]

Re: LG display sporadic screen issues

Post pic of the cap in question! I've also had a failing FRC board exhibit similar symptoms.

There is a high quality picture in an earlier post and a description of which cap he replaced in his post?