Samsung un43ru7100f no picture, flashing backlight

[a460guy]

Hey guys, ive got a samsung un43ru7100f that when turned on, only the backlights flash every few seconds. The guy i got the tv from said he took it to a tv repair place and said it needed a new lcd panel. What are your thoughts?

[neilc6]

Re: Samsung un43ru7100f no picture, flashing backlight

Flashing backlights on a Samsung is usually a sign of bad backlights. To confirm, unplug the cable between the power supply and main board and this will force the backlights on.

[a460guy]

Re: Samsung un43ru7100f no picture, flashing backlight

I did this and the backlights come on and stay on.

[neilc6]

Re: Samsung un43ru7100f no picture, flashing backlight

Second test is to only connect one side of the TV at a time and see if one side displays an image. Also see if the backlights stay on with both sides disconnected as well. Don't think this model has a tcon board so not sure what the outcome may be in models with integrated tcon boards.

[a460guy]

Re: Samsung un43ru7100f no picture, flashing backlight

This model does not have a tcon board. When only one ribbon is connected i get solid backlight and sound but no picture. This works with either ribbon. If only one is connected i get solid light and sound......i found a main board on ebay for 30 bucks so i will try that. But i would like to find the fault. Any ideas?

[neilc6]

Re: Samsung un43ru7100f no picture, flashing backlight

Could still be a bad panel. I've seen bad panels on models with integrated tcons that cause the TV not to turn on.

[Davi.p]

Re: Samsung un43ru7100f no picture, flashing backlight

Don't buy main board, you are here to receive advices so don't take your own decisions please, this can end in board scarce availability for others. If i'm not wrong this behaviour is due to a bad capacitor on one panel's small board, you have to remove them all one at a time and test, after that you tested for short on them, it exists a C56 or C53 start with it..

[Davi.p]

Re: Samsung un43ru7100f no picture, flashing backlight

In today's samsung models tcon is integrated with main..

[a460guy]

Re: Samsung un43ru7100f no picture, flashing backlight

Oh great! Yes i would rather find the fault. Here is a pic of the main board. Could you show me where the common fault area is?

[a460guy]

Re: Samsung un43ru7100f no picture, flashing backlight

Ok on the boards with the flex ribbon going to the panel.....i see...will check

[Davi.p]

Re: Samsung un43ru7100f no picture, flashing backlight

sorry , my cellular, i rewrite last sentence.
after that you test for short on them, if exists a C56 or C53 start with it..
To remove them if you don't have hot air then take a cutter with very sharp blade, put slow pressure on the basement of them and cut them away, very slow if not them flies away. Remounting of them's very easy, dont add solder only flux and use stilus iron.

[a460guy]

Re: Samsung un43ru7100f no picture, flashing backlight

What temp would you recommend for hot air? And thats pretty close to the ribbon cable....will that come loose if it gets hot? Also i checked all of them for short using the area in my pic marked red for ground. Is this not good enough to test? Or do i have to remove them and check there value? What should they be rated at?

[a460guy]

Re: Samsung un43ru7100f no picture, flashing backlight

Pic

[Davi.p]

Re: Samsung un43ru7100f no picture, flashing backlight

I don't have a professional hot air station, only a portable one that i've used few times, so i don't know, if i remember rohs tin melts at around 230 degrees european measure, for the ribbon you can mask it with aluminum foil, the area for gnd is ok but remember that not always shorts are revealed by a 3v lowcurrent tester, so you must remove them mandatory, the caps are 25v minimum, much probably them are those connected in parallel to Avdd tension of tcon so start with them, that are the biggest ones. Aftet each removing do a test of tv.