sony 55X850D black screen no front white or red led light.

[Ihandyrepair]

Hi guys

strange one
I have a dead Sony 55X850D
when plug in, black screen, no front white or red LED, no back light no screen

Voltages I get

3.3v LD/power and main board
reg 12V
reg 19V
3.3v on power on pin

no Tcon on
no tcon 12v
no BL_on

I do get BL_ERR 2.0v

I tried to bypass it by ground it but still get same symptom

I did also found a possible shorted cap on main board as it is showing 10 ohms when measure with meter
or is possible the chip next to it? Pin 5 and 6 are connected. where I measure another similar chip, the pin 5 and 6 are not connected

I just want to confirm with you guys before I take it out
also If you guys know what spec should I use as there is no label or markings on the cap

thanks

[nomoresonys]

Hm, check those other little caps right in that area and also any other caps that size and compare.

[nomoresonys]

This might not be the most precise approach but there's a longtime pro tech on youtube, that grabs one of those mlc caps off of his scrap boards that is the same physical size and throws it in there, he swears that he hasn't blown anything up yet, lol.

[lotas]

10 Ohm is a completely normal resistance, it can power the processor core, but there is always low resistance, if something shorted, the fuse would blow, what is the voltage on this inductor relative to ground?

[Diah]

this set from years 2016 with edge BL, which LEDs had build in zener diode one or more shorted so you have BL_ERR.
front LED could be turned off from user setting before it got fault at LEDs. since it send power_on.. so dont play with MB go head to take screen apart.. shorting BL_ERR to ground will not working at this set as it had frame dynamic Dimming.

[nomoresonys]

I agree with Diah, the bl-err is your clue, it can be very hard to tell if an mlc cap is bad unless you know what ohm they are suppose to read, getting very hot might be a clue to a bad cap. Have seen many shorted mlc caps on mainboards WITHOUT fuse being shorted.

[Ihandyrepair]

Thanks for the tip

here is another similar setup on the same board

Red circle is the one I am thinking possible shorted cap
now measured 39 ohms on caps end or chip legs 5-6

yellow circle
Both caps measure 7k ohms
and same for the chip next legs 5-6

as for the backlights error, won’t remove the line BL_ERR to LD board and ground on the main board side would at least try to turn on the backlights (by pass the error)
but I get no reaction

[Diah]

i did explained at my early post why grounding BL_ERR to ground didn't work...
if you tried it one more you will end by toasting yours PSU

[nomoresonys]

Think I would investigate those backlights, a guy here that works on a lot of sonys said he never had one with voltage at the bl-err pin that wasn't due to bad led/s.

[Ihandyrepair]

sorry I missed the part about dynamic dimming.
I guess Sony edge BL is different system than spread out led strips.
the 65X950G I was able to ground the BL_ERR to turn on the back lights to check if that is the real problem

thanks, got it, I will order the led first before taking it apart.
I will update you guys later when I am done

[nomoresonys]

I agree with Diah, the bl-err is your clue, it can be very hard to tell if an mlc cap is bad unless you know what ohm they are suppose to read, getting very hot might be a clue to a bad cap. Have seen many shorted mlc caps on mainboards WITHOUT fuse being shorted.

Lol, meant to say have seen many shorted mlc caps without fuse being open/blown.

[Davi.p]

why don't you write entire model numbers? It is useful for other one's searching..

[Ihandyrepair]

Hey guys
I took the panel off

borh edge led strips looks good
I tested with the led tester
none burnt
all seems to work
each section 56.9 to 57.0v
no sign of any led is not working

what should I do?

[lotas]

Why would you disassemble the backlight if you don’t even have a boot, the TV should have a standby mode, go into working mode and give an error, if the auxiliary is not working properly, but this is not the case, then the problem is in the motherboard...

[Davi.p]

test the psb with leds and no mb connected, force bl-on,.tcon-on
both psb and mb can be dried by an overvoltage.. surge at mains..

[nomoresonys]

Why would you disassemble the backlight if you don’t even have a boot, the TV should have a standby mode, go into working mode and give an error, if the auxiliary is not working properly, but this is not the case, then the problem is in the motherboard...

https://www.badcaps.net/forum/troubl...but-then-black
Well lotus it's right here in this thread so who is right? If the fault is on the mainboard WHERE is it??:

[nomoresonys]

ANY other opinions are welcome also, what do you guys think?

[Ihandyrepair]

I just noticed that if I unplug the cable from LD board to mainboard and power it on
the backlight will turn on.
so most likely the LD board is ok and issue could be the main board right?

[Davi.p]

i think yes, the mb controls the local dimming BL maybe, but mb software is KO maybe, so LD goes error and BL_ERR rises..

[nomoresonys]

Interesting, well I sure hope this one gets fixed, I gave up on mine that had bl-err, didn't care for the picture quality much when it was working, so didn't spend any more time on it, usually don't give up but just got sick of it.