Samsung QLED QN75Q8FNBFXZA inverted/negative color

[j879]

hi guys,

My 5 years old SAMSUNG QLED got color inverted somehow. I have tried reset, replace mainboard as well as the driver board without luck. The issue must be on the circuit on panel skinny board or so. For this model I could not find the dedicate T-con board so AS15 replacement is not applicable..

I have upload the pictures

Maybe I should measure the gamma voltage but I couldn't find the right place.

Any idea would be appreciated.

[lotas]

The problem may be in these protective diode assemblies (leakage, breakdown of one diode, short circuit to ground...) and in my opinion your resistor turned black because of them.

And check, if something starts to heat up too much, then there is a problem there.

[lotas]

The problem may be in these protective diode assemblies (leakage, breakdown of one diode, short circuit to ground...) and in my opinion your resistor turned black because of them.

And check, if something starts to heat up too much, then there is a problem there.

[nomoresonys]

So check that dark resistor, as suggested see if any of those diode packs are hotter than the others, if so remove it and recheck tv.

[j879]

The problem may be in these protective diode assemblies (leakage, breakdown of one diode, short circuit to ground...) and in my opinion your resistor turned black because of them.

And check, if something starts to heat up too much, then there is a problem there.

You are absolutely right. I use an infrared temperature gun measured the the right side as you mentioned with dark resistor, the temperature of the resistors are 10C higher than the opposite side.

Then I disconnect the ribbon cable to the overheated skinny board the color turns back normal without 1/4 of the display.

I guess next step is to find out the broken resistor or diodes. The temperature of the protective diode assemblies are normal compare to the other side. I'm going to remove one by one and see what happens.

Do you know whats the model number of the diodes assemblies?

Many thanks both of you!

[j879]

Got 2 more closer pictures now I can see the part/model number. Shall I remove the 6514Ps ?

[lotas]

https://www.badcaps.net/forum/troubl...ot-issue/page2

[Davi.p]

is still there someone that tries to repair a thing without swapping boards randomly?
i understand the MB but the Led control board...

anyway i don't understand the advice about diodes / resistor, those are not responsible of the colour of the pixels, my attention is on the serial flash on the right side panel pcb, is that the main tcon data? since tcon today are integrated to mb then needs only a different data for different panel and that's why data is on the panel, for me.. in other threads someone readed that mem and found it empty, that's strange, i find no reason to mount an empty flash.. it is not for storing errors cause it would be enough a standard eprom.. eventually try putting an 1kohm pulldown resistor between its clock pin and gground and test..

[lotas]

Got 2 more closer pictures now I can see the part/model number. Shall I remove the 6514Ps ?

Check the resistance on these legs relative to the ground with a multimeter, if it is low, remove it.

[Davi.p]

multi diodes are pertinence of clock signals, neighter clock signals nor voltages for line selection can alter the colours, especially let it being negative..

[nomoresonys]

Its been a while, didn't we see in the past a bad diode pack presenting a display like this?

[Davi.p]

I forgot that MB contains Tcon software in a serial flash, but the one on panel what is? Are source cof more complex than before and stores data on it?

[lotas]

It contains corrections for dead pixels of the panel; if there are no dead pixels in the panel, then the spi flash will be empty.
This is entered at the manufacturer's factory.

[Davi.p]

thanks

[j879]

ok, I removed 6514Ps one by one starting from D001 to D003 without luck..

blacked resistor remains untouchable.

Then I tried to tape out the ribbon cable from outermost side for 5 or 6 pins it fix the issue with minor missing interlaced lines.

Now the temperature went back to normal for the resistor and caps....

[lotas]

Tin the contact pads well using flux so that they do not short out each other.
And check this resistor with a multimeter, it should show 100 Ohm.

[Davi.p]

My bet is that the resistor heaten due to a bad cap, check every one in ohm mode, you also cool them one by one touching with a plastic wrapped ice cube..

[j879]

Cleanup the residue still the same

[Diah]

there are no bet over electronic repairs,, ... who like betting go play lotto .. don't play with users TV
i hope you didn't damaged the 3 ESD diode... if not put them back... we have here threat best masking method a person from japan... he did mask only 2 clk and have perfect picture just one thin line... this where no one can do against it when gate transistor at panel shorted

[nomoresonys]

Those diode packs aren't that important, they do cause more problems than they prevent.

[Diah]

Those diode packs aren't that important, they do cause more problems than they prevent.

sorry friends... this is wrong.. they are like cut circuit when panel API changed or from HDR to HDR+ they are watch dog to the gate transistor of panel... but dome time they are dummy and the gate shorted... but this doesn't men they are troublesome.