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

[nomoresonys]

Just a warning, be VERY careful if you do work on the mainboard, I ruined mine somehow, may have overheated the ram.

[nomoresonys]

Would be good to narrow this bl-err down, appears it is usually backlights but can be something else maybe? Wonder if Nick knows.

[Diah]

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?

we have in this forum threats with sony same things... BL_ERR generated by LD driver as its the parts monitor the currents pull up of BL LEDs,, disconnecting the LD just disable the monitore circuit.. mainboards send power on & BL_ON so where are the problem .. LOL
you test them on wrong way... you need to test each LED with DMM in diode mode in K A and reverse way to test the build in ziner are in takt and it pull 0.65 to 0.78

[nomoresonys]

we have in this forum threats with sony same things... BL_ERR generated by LD driver as its the parts monitor the currents pull up of BL LEDs,, disconnecting the LD just disable the monitore circuit.. mainboards send power on & BL_ON so where are the problem .. LOL
you test them on wrong way... you need to test each LED with DMM in diode mode in K A and reverse way to test the build in ziner are in takt and it pull 0.65 to 0.78

Yes, do this, definitely need to test those leds.

[Ihandyrepair]

we have in this forum threats with sony same things... BL_ERR generated by LD driver as its the parts monitor the currents pull up of BL LEDs,, disconnecting the LD just disable the monitore circuit.. mainboards send power on & BL_ON so where are the problem .. LOL
you test them on wrong way... you need to test each LED with DMM in diode mode in K A and reverse way to test the build in ziner are in takt and it pull 0.65 to 0.78

Well the thing that made me scratch my head is that I did take the screen apart, both edge led looks good condition,
And I used one of those led strip tester showed voltage draw
each led had like 6 sections
each section were drawing 56.9-57v
if one of the led was bad it would had lower or higher voltage draw, right?
also I thought maybe the trace or cable to led,
so I tested the led sections from the LD boards that has each sections test pads
same result
each section was drawing 57v

I was hoping it was the led strips or maybe the LD board
as they are cheaper than used mainboard
i don't get eBay or used online tv parts asking for $250 or higher
why I would spend $300 parts for this tv
where good used Sony tv are $300-500

[Diah]

do you have problem to understand what i am in ?? LED tester never never never discover LED with zener diode defect.. so the test should be with DMM in diode mode.. the reset up to you. at time you test all LED one by one with DMM and all show good then i can join again your threats... this is useless way for me at least.. as there other users include you go in guess on parts had nothing to do with BL_ERR... read again my last post. good luck

[Ihandyrepair]

thanks for your help but
you have to understand I am new in fixing tv and still learning.
I am guessing most of us are still learning.
you may be the best tech here but they way you tell me what to check I do not get it
but after reading your post more carefully and did more research
I am guessing you are trying to say this

https://youtu.be/rq-RwfDrU8c?si=PTnO4v7EDOq5GHZu

Like this guy showed cheap led tester can cause miss diagnosing led failure.

I guess I already bought the led strips
maybe I should just remove the screen again and test with the new led strip
or another way is order led ribbon cables, and test them to confirm if the tv will boot without the LD_err before taking the screen apart again

[Davi.p]

You are almost newbie in tv repairs if you didn't noticed that no status led errors are present, this clearly tells there is a bad software... truely, this is the sit. :
-bad software or bad emmc balls, bad software can mean also bad balls, so reballing is suitable
-bad Ram balls
-bad cpu balls
the sureness is to reball everything and reprogram emmc.. is this ok economically? i don't know...

[nomoresonys]

I believe Diah wants you to test those led backlights in this manner using the DIODE setting on the multimeter and testing each led so if you have for example 32 individual led backlights you would test all 32 not just from each end of strip: https://www.google.com/search?q=How+...86B18H4c8,st:3

[Ihandyrepair]

yes I am not worry people calling me newbie as I am new at this
but I do this as hobby only, so I don't think I will learn how to reball large chip like ram or cpu
if doing this full time, I think I should.
but something like small cap or resistors maybe ok

I look it this way.
if I get a tv for free or under $100
and if lucky is just something minor or fixable like led strips then why not spend the time as hobby
but I have to spend anything more than $250 to 300 for a used tv
I don't think it is worth to do it.

I guess there are 2 steps I should do for this tv
are the led ok? so Diah wants me to check each LED using diode mode
if they are ok, then most likely like davi mentioned bad software or chips = mainboard

[nomoresonys]

That seems like a good approach, mainboards can be very hard to diagnose and fix even for the best pros.

[nomoresonys]

yes I am not worry people calling me newbie as I am new at this
but I do this as hobby only, so I don't think I will learn how to reball large chip like ram or cpu
if doing this full time, I think I should.
but something like small cap or resistors maybe ok

I look it this way.
if I get a tv for free or under $100
and if lucky is just something minor or fixable like led strips then why not spend the time as hobby
but I have to spend anything more than $250 to 300 for a used tv
I don't think it is worth to do it.

I guess there are 2 steps I should do for this tv
are the led ok? so Diah wants me to check each LED using diode mode
if they are ok, then most likely like davi mentioned bad software or chips = mainboard

I wouldn't make fun of you, I'm new to this myself. I have very seldom met a sony that was an easy fix.

[Diah]

i asked to testing LED one by one as nomoresonys said.. not to replace LOL you can learn its no difficult matters... if yours DMM with 9V Battery , on K A ithe led will light very dim.. and when you do reverse the probe it will show you the reading on zener diode... so you will know if this shorted or open or in takt at good reading.

yours MB sending Power ON and BL ON so what kind of SW issue or BGA to do when it send signal so funny.....there are BL err high so the first things need to be sure this LED BL are good not to go destroying the MB.... front LED indicator can be turn off from user menu... who don't know about sony android then should have one and learn how it work.

[Davi.p]

my advice don't risk much with broken sets, the luck rarely presents it, in the very wide faults types field, this was my error many and many time, therefore you end filling house with hard to fix beasts.. better buy them with no urgent needs.. and if you have much time to dedicate..
and last.. today tv are more problematic than previous, don't expect fast repairs, them are hard bones..

[nomoresonys]

I'll just say that if you are paying 100 bucks for a non-working tv, you better make sure you can at least get that back in parts OR you might be in for a very expensive hobby.

[Ihandyrepair]

haha yeah
I would only pay $100 if I can see the screen working for Sony
other would be $50 or free

I can believe some people asking cracked screen for 250-300,

before I got few free LG or samsung were tv works fine just the back light was burnt
but I don't want to do samsung edge BL anymore as I found most of them after burning the LED you take it apart
you see the diffuser cracked or plastic sheets all metled so after replacing the BL
the tv screen still look like crap all lights everywhere

as for LG, spread out back light not too bad after replacing the BL, everything looks good
only down side is you don't get as much as Sony tv

I got lucky few times were I got Sony tv
one 55 inch was replacing the main board. and I was lucky were local guy was selling the mainboard due of cracked screen so costed me only $45 for the tv to fix
now I am using it as computer monitor

another one was free Sony 65, owner unplugged it before updating was finished, stuck in booting. but I was lucky just did a hard reset and tv was working. I didn't even had to use my screw driver on this one.

and last one was the X950g, with flashing red light, and I was able to ground the BL_err and tv start so I was able to confirm the back light had 1 dark spot, burnt 2 led most likely
which I will replacing it later on.

now stuck with this one,
but now I look at this way
if the led are still ok, then most likely I will have to wait until I get a cheap or free mainboard like from a cracked screen. in order to fix it.
the worst part as nick said, the 55x850d support has been discontinued. so I can't find a newest firmware to download.
and looking at some complains about this model, I should not spend too much for it. as there is no more updates.

I am sure how many of us have few broken tv in the garage waiting for cheap part or another way to diagnose the problem
and the wife is mad about it
right?
haha