55" QLED QE55Q60T Turns on after 1 minute the picture goes bad and get in boot loop

[burbutsalos]

Hello ,
The issue with this set is that it turn on just fine and after a minute or so the picture shows either vertical lines or turns half black and from that point on starts a boot loop.
If a let the unit to cool down for a minute the same pattern starts again. i had exactly the same mainboard as a spare and replaced it but nothing changed.

Any ideas what to check?

[Davi.p]

I would have said bad mainboard (processor soldering), are you sure 100% about the repl. mainboard? If it's ok is probably something on the stripe boards on the panel..

[Diah]

wrong.. the new style blind my eyes... QLED i read it OLED LOL

[Davi.p]

IN-Stop on a Samsung.. very well.. VERY WELL...

[EazyBone]

wrong.. the new style blind my eyes... QLED i read it OLED LOL

You know you can change it to dark mode now right?

[Davi.p]

Thanks EB..
I feel like saying, there are no longer the good sites of the past!

[burbutsalos]

Yes the mainboard is from a completely identical set with broken screen (same panel type same mainboard type ). I did some tests on the panel pcb,s realized that some set of capacitors (2 on each cof ) short after some time.

When you turn on the tv all is ok.

After the 1 minute time those caps start to beep (short) the display goes bad and the boot loop starts with the same symptoms only this time since something has warmed up the loop happens within a few seconds and not a minute as the first rime when the set is cold

[Davi.p]

to clarify you put the DMM in continuity mode across a capacitor and after some time of tv ON the DMM beeps?

[burbutsalos]

actually yes !! But i managed to do some more tests and it gets even more confusing !!!! I tried the testing points on the pcb boards .
What i get makes no sense to me at least. Testing for shorts on diode mode ido not get a complete shorting beeping sound from my multimeter but rather something like a pulse sound this happens when i test vss with all the ck 's 1-8 stv with all ck's vss with stv .
And the clocks amongst them also.
The tv stays on on this status with only a very fade black horizontal line in the middle of the screen .from the right side of the panel gradually fading to normal picture.to the left side
This line also seems to be vanishing every 2 seconds aprox. On a certain point the screen goes half black and freezes and at that time the capacitors seem short and the set reboots.(the ones with the arrows ..the same pair in all cofs sound short)
Now for the craziest part !! I managed to decrease contrast and brightness and also changed the tv screen settings from dynamic to typical which is less bright. The tv stays on practically forever !! As soon as i revert to the more bright settings the issue appears again. !!
I did not changed any backlight setting. During the time that the tv stays on with the lowered settings i can still get the <<semi-short>> sounds from the testing points...
Is there any logic in all of this ?????
,

[Davi.p]

The tests you made are confuse and out of technique, what you have to do is to unsolder one by one the protection diodes in photo T1-Tx.. and after each one test the tv.. already seen this defect..

[burbutsalos]

Thank you Davi.p . What you say is to desolder one after the other to see if the tv stays on in the end? You say you have seen this defect is it caused by baδ diodes?
Also since i have the same broken panel if fthat is the problem should i try to use diodes from the broken panel f they are the same?

[nomoresonys]

Just test those caps in ohm mode, what do you get?

[Davi.p]

burbutsalos, YES to all questions.. pay attention to the polarity.. T stays for TVS diode.. (Trans Voltage Suppressor?) them goes short or leakage after surge.. NEVER touch the border of a TV with naked hands or discharge them before..

[burbutsalos]

nomoresonys when they short they all show about 16 ohms.
Davi.p .. I tried desoldering one by one the diodes you sujjested . unfortunatelly no luck. Now it is on a boot lloop . If a mask with tape somethinh from the riight pcd i might just get steady backlight and sound but no pictrue. Iwill try to resolder then but itseems very difficult to do.

[Davi.p]

i told you desolder one by one and test after each