Has anyone ever repaired a bad panel driver? - Badcaps

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johniwad

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Country: United States
#21

03-06-2018, 08:47 PM

Re: Has anyone ever repaired a bad panel driver?

From the looks of it both driver boards have the same components except the right one. The pictures are of two ics that are only on the right driver board. I couldn't find any datasheets.
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johniwad

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#22

03-06-2018, 10:24 PM

Re: Has anyone ever repaired a bad panel driver?

Marked:
Standby OFF: 8v
Standby ON: 13v
LED Driver Output: 195v/161v

Actual Voltages:
STB: 8.79v
ON: 12.79v (all marked A13v pins)
PS ON: 3.3v
LED Driver Output: 171.5v
T-Con: 12.53v
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lookimback

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#23

03-06-2018, 10:27 PM

Re: Has anyone ever repaired a bad panel driver?

Did you test all the MLCCs and resistors on the driver boards for shorts/opens?

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johniwad

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#24

03-06-2018, 10:32 PM

Re: Has anyone ever repaired a bad panel driver?

I know it's unlikely for both panel driver boards to go bad so im thinking components that is not common with the other. The pictures are of two ic I found on the right driver that's not on the left. I am unable to find datasheet for these ics.
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lookimback

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#25

03-06-2018, 10:46 PM

Re: Has anyone ever repaired a bad panel driver?

I'm thinking the one is the edid eeprom. You wouldn't need a problem with both boards to have no picture on either side.

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freakaftr8

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#26

03-06-2018, 10:52 PM

Re: Has anyone ever repaired a bad panel driver?

Originally posted by lookimback

I'm thinking the one is the edid eeprom. You wouldn't need a problem with both boards to have no picture on either side.

I always thought that as well until I ran into the issue with the Sony XBR55X850B with the LG panel.... I believe now that IF a MLCC is shorted o n one side, it can affect the other.

I also have a Sony XBR75X850C that had a shorted MLCC on the driver board, I fixed it but still fail to get a picture unless I force the tcon my jumping 12v to AVDD. I still 75% think it's a tcon problem.... Even thou I've replaced it with 5 different tcons and still no picture, but there's no voltage from the tcon out to the panel bu5 gets 12v in to tcon.

Did I leave the soldering iron on?
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lookimback

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#27

03-06-2018, 11:06 PM

Re: Has anyone ever repaired a bad panel driver?

Originally posted by freakaftr8

I believe now that IF a MLCC is shorted o n one side, it can affect the other.

That's what I meant. I think a shorted component on one affects the other through the T-Con. Maybe it causes something to go into protect mode, or maybe just sinks the voltage. In the case where you can't get a picture with either ribbon disconnected, perhaps there's something on one side which the other side needs and gets through the T-con. I've seen panels where you could disconnect one ribbon and get a half picture on the other side, but disconnect the other and just get a white screen on the connected side.

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johniwad

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#28

03-07-2018, 12:05 AM

Re: Has anyone ever repaired a bad panel driver?

Originally posted by lookimback

That's what I meant. I think a shorted component on one affects the other through the T-Con. Maybe it causes something to go into protect mode, or maybe just sinks the voltage. In the case where you can't get a picture with either ribbon disconnected, perhaps there's something on one side which the other side needs and gets through the T-con. I've seen panels where you could disconnect one ribbon and get a half picture on the other side, but disconnect the other and just get a white screen on the connected side.

I tried disconnecting ribbons one at time with no change. I will try testing MLCC and resistors tomorrow.
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lookimback

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#29

03-07-2018, 12:16 AM

Re: Has anyone ever repaired a bad panel driver?

Originally posted by johniwad

I tried disconnecting ribbons one at time with no change. I will try testing MLCC and resistors tomorrow.

Did you do it with the power off, and then turn it on after disconnecting? It usually won't work otherwise, and also hotswapping can damage the panel. I fried a 60" Sharp smart TV once by not turning it off before connecting the ribbon cables. Valuable lesson learned that day.

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johniwad

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#30

03-07-2018, 09:44 AM

Re: Has anyone ever repaired a bad panel driver?

Originally posted by lookimback

Did you do it with the power off, and then turn it on after disconnecting? It usually won't work otherwise, and also hotswapping can damage the panel. I fried a 60" Sharp smart TV once by not turning it off before connecting the ribbon cables. Valuable lesson learned that day.

Yes I did that and I just checked for shorts I can't seem to find any. Not sure about those two ics though. I think I'm about to throw in the towel on this one. I really appreciate everyone's help and suggestions.
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freakaftr8

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#31

03-07-2018, 03:13 PM

Re: Has anyone ever repaired a bad panel driver?

You could always try applying 12 V to AVDD Before you give up to see if there is some kind of a picture there

Did I leave the soldering iron on?
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lookimback

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#32

03-07-2018, 03:16 PM

Re: Has anyone ever repaired a bad panel driver?

Also, it's possible the main board isn't sending any signal.

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Davi.p

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#33

03-08-2018, 01:02 PM

Re: Has anyone ever repaired a bad panel driver?

It's not the right way to test a panel. 1st=test supply tensions on the tcon (attached and detached), 2nd=test those voltages on the panel's boards. If there are no tensions on tcon it's unuseful to do pass 2.

Last edited by Davi.p; 03-08-2018, 01:16 PM.
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lookimback

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#34

03-08-2018, 02:59 PM

Re: Has anyone ever repaired a bad panel driver?

I've had a couple occasions where I had another tv with the same LVDS pinout and put them back to back and plugged the LVDS cable from one to the other. Picture wasn't right, but it told me if I had a main board problem (no T-Con) or a panel problem.

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