Philips 55PUS6262 no picture

[mrsith]

Hi. I have seen a thread with this TV model, but the solution wasn't applicable to my set unfortunately.

I got the set very cheap with problems on the right side of display - it was flickering and fuzzy with whitish noise. After a bit of play I have noticed that the set is fine with only left LVDS plugged in - but, unless I pressed the LVDS connector (on either side which is strange), there were some purple artifacts appearing. Decided to replace T-Con with both LVDS tapes (suspected bad tapes). After replacing them - same effect, with purple artifacts disappearing when pressing LVDS conn. After a bit of playing it stabilised though - artifacta disappeared.once and for all, so I have half screen working fine.
Found a post on badcaps with this model - tried updating the software but as expected - no change.
Tried the cut tape, my beloved method - either no picture at all, or flickering white screen that blinks faster and faster then shuts off (just the bad side).

Ohm-measured caps on LCD panel board - there are 12 ~34ohm caps, 10 of which are situated in the same.locations next to bond tapes. There are no other SMD's on board rather than caps and resistors. All the ICs, testpoints etc are on T-Con board.

Not sure where to look next. I'd suspect something bad on T-Con, but it has been replaced. Could you please guide me what should my next step be?
Many thanks and kind regards

[nomoresonys]

Re: Philips 55PUS6262 no picture

did any of those 12 caps test shorted?

[nomoresonys]

Re: Philips 55PUS6262 no picture

34 ohm seems pretty low.

[mrsith]

Re: Philips 55PUS6262 no picture

did any of those 12 caps test shorted?

All of them had ~008 on one side and ~040 on another (diode testing). For some reason my multimeter doesn't beep at all.

34 ohm seems pretty low.

The rest of the caps rise to infinite ohms as they should so I'm pretty sure something shorts them. Seen some guides on what to measure but all of the IC's and testpoints are on T-Con board which has been replaced.

[nomoresonys]

Re: Philips 55PUS6262 no picture

well maybe put it in diode/continuity mode, put probe on each end of cap if it reads 000 or close it's probably shorted.

[nomoresonys]

Re: Philips 55PUS6262 no picture

in diode mode you can put one probe on ground, the other on either side of cap, should probably read close to 000 on one side and I or l on the other, if you get close to 000 on both sides it's probably shorted or there's a short nearby.

[mrsith]

Re: Philips 55PUS6262 no picture

Like I said, in diode mode (ground-cap testing) I am getting ~040 on one side and ~008 on another, on all of low-ohmed caps. I'll check probing on both ends on cap then.

[nomoresonys]

Re: Philips 55PUS6262 no picture

those readings are not what I get when testing. ARE you testing as posted in #6?

[mrsith]

Re: Philips 55PUS6262 no picture

Had to slightly calibrate my multimeter, but finally I have somewhat normal readings:
Cap leg to leg diode - healthy caps show ~670 or above, all of the 12 sketchy ones ~035.
Cap leg to ground - healthy are ~600 one leg, 000 other, sketchy ones ~030 / 000
Still not sure how to identify le source of the problem properly.

[nomoresonys]

Re: Philips 55PUS6262 no picture

can you post a good picture of those? do any of them get hotter than the others, sometimes it's only one bad cap, if they are big enough to work with, maybe remove one on the end and test it out of circuit, see if you have the same readings.

[mrsith]

Re: Philips 55PUS6262 no picture

I'll grab a thermal camera from my friend and try to locate the bad guy then. Will post the pics tomorrow.

[mrsith]

Re: Philips 55PUS6262 no picture

There are pics attached - encircled bad caps, one shows place from which I desoldered a bad cap (didn't change anything). Most of them are in pairs, small + big just next to each other. Just differs slightly on either end of the board.

I didn't manage to get ahold of thermal cam today, so I've used a pistol-type thermometer, no place on board seemed to be warmer than 19.x°C, not a single piece warmer than the others around. Used my fingers to confirm that 😁

[nomoresonys]

Re: Philips 55PUS6262 no picture

ok, did you test that cap now that it's off the board? test the pads it was soldered to also.

[mrsith]

Re: Philips 55PUS6262 no picture

Sorry for late response.
The pads are showing sort, I am not getting anything when trying to measure caps outside the circuit. I'll continue desoldering them one after one in hope that the short will disappear along with one of them.

[mrsith]

Re: Philips 55PUS6262 no picture

My hopes were answered, the short is gone along with one of the caps. Grabbed one looking the same from spare T-Con board from this TV, and got healthy measures on all components. Tried to turn the TV on but still no picture. After disconnecting bad side LVDS, I am getting half picture with purple artifacts again, and again they react on pressing the LVDS connector or the tape itself. I'll try playing around with this to get a stable half good picture, then I think I'll try scotch taoe method again, maybe without the short it'll work? Also will doublecheck everything with DMM again.

[nomoresonys]

Re: Philips 55PUS6262 no picture

sounds like a solid plan of action.

[mrsith]

Re: Philips 55PUS6262 no picture

So, the half picture kinda stabilised after a bit of play, if I mess around the tapes or the TCon itself it likes to wiggle some purple stuff on the screen. Decent enough for tests though.
Cut tape method didn't return any joy unforunately. I noticed however, that with only bad side connected the TV shines white on good side with no picture on bad one. With the short present, it was all black, so it's a tiny step forward I guess.
Any advice where should I look further? Many thanks in advance!

Edit: I did some measurements. Got 3.3v on VCC, 1.65v on VCC18, 16.6v on VDD. VGH even and odd both jump between 28 and -7v every couple of seconds. VGL_2 is missing entirely.

[nomoresonys]

Re: Philips 55PUS6262 no picture

maybe check the caps on the tcon if you didnt, test same way as the others.

[nomoresonys]

Re: Philips 55PUS6262 no picture

ok, so if you have 2 tcons to work with maybe try the original, you can see if there's a difference in those vgh readings and such.

[mrsith]

Re: Philips 55PUS6262 no picture

The original TCon was used as a source of caps so it won't be relevant. Didn't find anything wrong or unusual on the new one, everything I measured seems OK.
Is there any chance that the original short on panel caused some IC on both tcons to fail?
BTW the voltages are the same with only good half of the screen connected.