KDLr50550a backlight fails

[milkman6453]

Sony Bravia
KDL50r550a

Hello there everybody! I have been having on and off issues with this tv for a few weeks now.

At first i let the a company try to fix it, they blindly replaced two boards, the Main board and the power supply.

It fixed it for a few days and now im having another issue and want to try it myself.

Originally i had a error code, this time the screen will come on and work, then i lose video but continue to have sound. It passes the flashlight test, as in i can see whatever is on the screen with the flashlight on it.

I have an "OK" ability to test and diagnose with my meter and solder pen. Just lack the knowledge as to which path to take.

Here are some picture of all of the board on the Tv, the images were too large for the badcaps forum, i uploaded to imgur, is this acceptable?

You jut hit next or previous at the top of the page to cycle through, there are 10.

Any help would be GREATLY appreciated!!

http://imgur.com/F41Yyxm,DMa4pH0,pUe...NitvV3,oZKYvBY

[milkman6453]

Re: KDLr50550a backlight fails

Just checked the parts i can see that are fuses, all have 0.1 ohms across except for one on the tcon board which is a 3amp and it reads 0.2 ohms

I had one dim or dark led in the corner. Is there a way to test for a shorted :LED?

[milkman6453]

Re: KDLr50550a backlight fails

Some information I gathered this morning.
Now that I have the TV laying down on a sheet in kitchen table the back light will not cycle off.

There is a ln audible buzzing coming from the tcon and led inverter boards.

Here are some voltages
Bl on is 3.2 volts
Bl err is 3.2 volts
Reg 12v is 12.77 volts.

Any advice

[milkman6453]

Re: KDLr50550a backlight fails

I got into the "self-check" menu, it says no errors have been present, although my BL-err is at 3.3v

After removing the back of the set and picking it up and down the backlight refuses to shut down on me again.

Could it be the act of putting the back on it and tightening the screw be causing a short to chasis somewhere?

If so how could i locate it?

[Ltank]

Re: KDLr50550a backlight fails

I don't know the backlight illumination the set has. Normally led seds the P.S. shuts down. This one has Picture and is dim across the width of the screen. I say it's a bad bulb..

[cashkennedy]

Re: KDLr50550a backlight fails

Is the screen (backlights) turning off in roughly 2 seconds? Then you most likely have a problem on the backlight boards, or bad bulb. You can disassemble the set to the point where you can see the bulbs then when it turns on for 2 seconds see which one isn't turning on. It is extremely easy to break an LCD panel when you disassemble it to the point where you can see the bulbs, probably about 1 in 5 people crack it at that point.

[milkman6453]

Re: KDLr50550a backlight fails

When it was happening it would stay on for about 10 seconds. Then lank screen and the indicator light stays green sounds continues.

Ever since I disassembled the rear and check voltages and wire connections it has worked fine.

I saw how to remove the front bezel, couldn't quite see the leds. I don't want to break it!

[cashkennedy]

Re: KDLr50550a backlight fails

Ah, so this is an LED backlit set. Ignore me and the other guys mention of bulbs...

Would probably need a closer picture of the LED control board (above the power supply) to have any ideas on what to test. But I have never worked on an LED set before.

edit: Your IMGUR has really clear pictures, and you said you tested the fuse on the board. There is also test points next to both connectors on the board, but since ive never worked on LED idk if you can test them.

[milkman6453]

Re: KDLr50550a backlight fails

There's one point that says vled, it didn't test it as I was searching here for what it might be.

Since the TV wouldn't act up for me again I can't really diagnose it! Pain in the butt