Samsung QE65Q8F not turning on

[unimatrix93]

Dear everyone I have a QE65Q8FNAT Samsung TV with one connect box.

The symptoms are the following:
- The TV has stand-by LED, pressing the power button only flashes it once, holding or pressing it multiple times makes it disappear but you can hear a faint relay click from the one box and the red standby led comes back.
- No backlight or sound comes from the TV.

I took apart the one box, suspecting it to be faulty but I couldn't find anything, but I grabbed a spare working one connect box + cable from my friend to try it. Same symptoms.

So There is something on the mainboard or the PSU.

- I took some measurements on the PSU and I found that 13V is missing, 350V is present.


- The CPU heatsink is slightly warm to the touch.

Anything I should check or measure?
Thanks in advance!

[Diah]

I tried pressing down on the CPU,EMMC, and the two RAM ICs while pressing the power button, did not help sadly. I will try the compressed air trick you meantioned on monday however.

why you go to this point and you have at first start script from SPI the front LED faint... ? remove load such wifi or BT, check and test yours LED BL, as they are edge and from 7 years in work. if all are fine then as i said no communication between SPI and SoC and this this is BGA, with pressing bring nicht

[Diah]

Panel or BGA on main SoC at MB

[unimatrix93]

Panel or BGA on main SoC at MB

If it's the panel, disconnecting the LCD ribbon cables should make it start no?

If It's BGA, reflowing would help it or I should get a new IC (If it's even possbile.)?

[Davi.p]

Panel problems gives 2 blinks.. investigate on the missing 13v, check the power supply at bench..

[unimatrix93]

Panel problems gives 2 blinks.. investigate on the missing 13v, check the power supply at bench..

I took out the PSU and I check around on it.

Meanwhile I noticed that the standby led does this after "forcing it" to start:

VID_20251016_103047

Disconnecting the panel does not changes it.

[Davi.p]

checking the power supply is not simple visual check, you need to force it fully on and test it alone in the bench, checking outputs..

[unimatrix93]

checking the power supply is not simple visual check, you need to force it fully on and test it alone in the bench, checking outputs..

By checking I meant measuring diodes, caps, etc.

[Davi.p]

You say the 13v is missing, so try it before checking components, it is not the right mode to proceed, check if alone the 13v comes out..
you need a 3v around zener, a 2,k2 resistor or similar..

[Diah]

samsung has no blinking code..( its Native Linux ) start script at SPI when it start after pressing the power STBY LED will blink once at each step of starting script.. this mean there are no communication between SPI and main SoC... this is first ABC of how TV start working.

[unimatrix93]

samsung has no blinking code..( its Native Linux ) start script at SPI when it start after pressing the power STBY LED will blink once at each step of starting script.. this mean there are no communication between SPI and main SoC... this is first ABC of how TV start working.

Turns out my multimeter probe is damaged, so after replacing it I managed to find out that both 13V and 18VAMP is present on the PSU.

So it's looks like the MB (SOC?) after all, only symptom is the periodically clicking relay in the One connect box.

EDIT: I took off the heatsink from the mainboard check it. Plugging in the system in the socket causes the SOC to become blazing hot instantly.

[lotas]

samsung has no blinking code..

Modern Samsung TVs have it.

[Davi.p]

Do not judge by this test that it is bad cpu, in such a powerful set the cpu is powerful and draws much current, it is nornal that it needs the heatsink, judge it with it, i guess there possibly be a software error, could also be an hardware emmc or ddr error or something else

[Diah]

Modern Samsung TVs have it.

this TV from 2017 and work on Tizen 3.0 ... where are the modern at it !

[Davi.p]

Do not listen him, i remember Samsung lcd from early 2010 with led error codes.. this is the normality, only Samsung usually never rendered public its decoding

[lotas]

this TV from 2017 and work on Tizen 3.0 ... where are the modern at it !

What does Tizen 3.0 have to do with this? Samsung has its own error codes, regardless of their version, just like Sony, and regardless of the Android version. The answer was that Samsung has its own error codes!

[Diah]

Do not listen him, i remember Samsung lcd from early 2010 with led error codes.. this is the normality, only Samsung usually never rendered public its decoding

usless talking with you... thinkl as you both... his LED faint. where are the F°°K error

OP: lets back to the issue show please yours mainboards with out sink... and test the SPI Pin 8 if it had 3.3V and remain 3.3V after you pressing the power

[unimatrix93]

usless talking with you... thinkl as you both... his LED faint. where are the F°°K error

OP: lets back to the issue show please yours mainboards with out sink... and test the SPI Pin 8 if it had 3.3V and remain 3.3V after you pressing the power

Here is some photos of the MB and the two Winbond IC:


Both IC has 3.3V on pin 8 right after plugging in main, and after pressing the power button too.

[Davi.p]

you need to try and reprogram. first the lower one of spi eprom

[unimatrix93]

I have a CH341 programmer but I don't have the bin file for it sadly

[Davi.p]

You can try desolder it, read it when freezing with compressed air can, and rewrite it.. before it try booting the set when pressing down the cpu, the emmc, the two ram, in turn..