No Video on my Samsung 55"

[MG36]

Been reading up on this issue and thought this was the best forum to ask for some others' insight.

I have a Samsung 55" LN55B650T1FXZA and the video has gone out. I still have sound. I shined a flashlight on the screen and can see the image. I have all the video inputs and the same symptom occurs. I replaced the backlight inverter board and no luck. I wanted to test the HV (750v ~) out of the power supply but the people I bought the inverter board from said no need to they are certain it was the PWR SUP now. Any suggestions???

[tom66]

Re: No Video on my Samsung 55"

Do not attempt to measure the output voltage with a DMM, it will result in a fried DMM!!

Simple, if you do not have any light, the inverter is bad, because if it is good, you will at least see a brief flicker of light.

You can test the main board by disconnecting the connector between the main board and power supply. When you plug the set in, the backlights should come on at full brightness.

Pictures of the power board will help us help you. There is a common issue with a diode failing short on the power supplies for these TVs causing no backlight.

[MG36]

Re: No Video on my Samsung 55"

Which cable should I disconnect the pink/white or the main that has the 12V stand by riding on it. I did test that signal (12.45V). I agree with not using a DMM I knew it would blow it. I asked the company I bought the backlight inverter board from if there was another signal to test but they did knot know. Will attach PIC soon.

[tom66]

Re: No Video on my Samsung 55"

If you get me a picture I'll show you where to disconnect.

[MG36]

Re: No Video on my Samsung 55"

PIC Attached

[tom66]

Re: No Video on my Samsung 55"

Bottom left. Just unplug it, then plug the TV power in.
https://www.badcaps.net/forum/attach...8&d=1369759549

[MG36]

Re: No Video on my Samsung 55"

So just to be clear; unplug the "bottom left cable" plug TV back in then turn it on to see if the panel light up? I will try when I get home and report back tomorrow.

THANX

[tom66]

Re: No Video on my Samsung 55"

Plug TV in. You won't be able to get it to turn on (with no mainboard power) but the backlight should light up.

[MG36]

Re: No Video on my Samsung 55"

Well no luck with those steps. I unplugged the "bottom left" cable that cable went to the video board (no back light lighting up). I tried unplugging the cable to the backlight inverter board just to try something else and nothing. I still have the same symptom.

[MG36]

Re: No Video on my Samsung 55"

tom66
Since my experience is with communications systems I am not used to TV troubleshooting. Was wondering if there any other steps I could take to isolate my problem and ensure that I either purchase the correct component or board?

Thanks for all the help thus far.

[tom66]

Re: No Video on my Samsung 55"

Since your backlight flashes when you unplug that cable, the problem is either on the inverter/power combination board, or the bulbs in the panel themselves.

[MG36]

Re: No Video on my Samsung 55"

So since I have replaced the inverter boards twice with known good ones I can assume it is the power board next. What component should I replace or should I replce the entire board?

MG36

Again thanks for all the help.

[tom66]

Re: No Video on my Samsung 55"

There is no "inverter" board on this set -- there is a long thin green board, a balance board, is that what you replaced? If so, can you post a picture of it?

[MG36]

Re: No Video on my Samsung 55"

Attached is what I replaced twice with no luck.

[tom66]

Re: No Video on my Samsung 55"

Oh, OK. Those are balancer boards.
Can you get a closer photo of this connector?

[MG36]

Re: No Video on my Samsung 55"

Funny the Shop Jimmy folks have been calling these the back light inverter boards.

[tom66]

Re: No Video on my Samsung 55"

Can you measure the pin voltages on "FB"? The two gold pads directly above can be used. Set your meter on DC volts, 20V scale. Reading >2V is suspect.

[MG36]

Re: No Video on my Samsung 55"

I will take the measurement tonight and post. I did take the VCC and it was 12.45V (stand by V I believe). Also, there is FB1 and FB2 do they both require >2V?

[tom66]

Re: No Video on my Samsung 55"

Sorry, yes, please check FB1 and FB2.

[MG36]

Re: No Video on my Samsung 55"

tom66

thanks for the help so far

FB1 and FB2 = 0V