Sony XBR-52LX900 BL_ERR

[Nicktronic]

Alright, I checked the strips and found 1 shorted zener on a new strip. So, I used 1 old strip and 3 new ones, and tested every single LED on all 4 strips. ~2.6VDC/LED. Then I tested every zener on all 4 strips, ~0.76VDC/zener. The LED strips are good. Installed them in the TV, same problem, 6 blinks. On power up BL_ERR is 3.3VDC......then drops to 0 briefly as BL_ON goes to 2.6VDC.....then BL_ERR goes up to 3.3VDC.....6 blinks. Aaaaarrggghhhh....

Unless another zener/led failed on power on, I don't know what to do next...

[Nicktronic]

Diah, where are you, I need your help! :P

Does anyone happen to have the schematic for the power supply board for this model?

Thanks

[nomoresonys]

Nick knows sonys, good video there, he shows how to check mainboards, 44-47 minute mark is very helpful in troubleshooting: https://www.youtube.com/watch?v=Enf8AEjeMbs

[Nicktronic]

Thank nomoresonys, Ive seen his videos in the past and used his services as well. Great guy and smart!

I haven't found anything that talks about this older molder XBR though.

[nomoresonys]

I believe early on in the video, he says its about the xbr and xr models from around 2015 thru 2020. Looks like you have about a 2010 so bound to be some differences.

[nomoresonys]

Looks like there may be several small fuses on the mainboard labeled like F3701 etc, maybe check all those.

[nomoresonys]

Are you still getting "V out to BL is briefly hits about 280VDC then drops to about 111VDC" after you changed it up?

[nomoresonys]

Maybe try this trick, just to see if it might still be an led issue: not your exact model but same concept: https://www.youtube.com/watch?v=T3VRvQUB_DQ

[Nicktronic]

OK, I will, but I've checked the LEDs fully and made sure all LEDs turn on and I get a good diode measurement when I checked all the zeners. What's happening is, yes, the TV initially turns on and tries to drive the backlights (280VDC), but then a BL_ERR fault pops up and kills the startup. Maybe I can ground the BL_ERR signal to the Main Board.....but that doesn't stop it from being generated on the Power Supply board..which may in turn limit the current to the backlights, but I'm not sure...it's tough without a schematic.

[Davi.p]

it's tough helping you with no full photos (as per post #7)...

[Nicktronic]

Sorry, I read the stickys about file size and posting pics. Thought I met both those requirements with the initial photos and subequent photos. I'll post some more with better detail.

[Davi.p]

oonly the back of power board..

[Nicktronic]

Hey guys, here is the Power Supply Board schematic. I'm going to work my way back from the BL_ERR pin on the connector to the Main Board and see if I can find the exact source of the error signal. Open to suggestions/direction obviously.

[Diah]

this post still in place
don't trust what you buy bow days

[Nicktronic]

I did check them all....see post #21. You still believe it is a bad LED/zener? I'll check again I guess

[Nicktronic]

Checked all strips again. 2.5VDC LED, 0.75 ZENER.

I short STB3.3 to Power ON and BL_ON. As I've said before I get ~287VDC on OUT1 (Two strips in series) and ~290 on OUT 2 (Two strips in series). I measure ~125VDC on each strip individually. BL_ERR is 0VDC. Do the strips have to be attached to the TV same as the original way? Originally they were screwed to a bracket, but I used double sided tape for the new set. Does that matter?

[Diah]

you have cocktails strips

[Nicktronic]

lol, what?

[Nicktronic]

Power Supply Board, both sides....see attached.

[nomoresonys]

Look over all the solder joints, some of them don't look too great, add a little solder to those that look suspect, careful not to bridge anything, search images bad solder joints if needed, it's something that should be done early in troubleshooting becuz sometimes it IS just a bad solder or two.