Bl in Samsung will flash a couple times, then shut off

[edugimeno]

Hi there!

I have this Samsung LE32A336 TV that when you turn it on, it works fine for a second, then backlight flashes off/on for 3 or 4 times, and then definitely off until you turn the TV off again

I guess the BL driver is "trying" to keep it up and sees either lower or higher current flowing to the led strips, but just to be safe, is there any way to identify if the problem is in the led strips (open or shorted LEDS) or in the BL driver IC before opening the front side?

Thanks a ton!

[nomoresonys]

Re: Bl in Samsung will flash a couple times, then shut off

usual test for samsung, unplug tv from power, unhook cable from powerboard to mainboard, plug power cord back in, if backlights come on and stay on then backlights and powerboard are probably ok.

[edugimeno]

Re: Bl in Samsung will flash a couple times, then shut off

Will BL turn on with main board unplugged? Shouldn't the B_ON be driven on by the main board? Or maybe it's pulled up high from the PS?

Thanks

[nomoresonys]

Re: Bl in Samsung will flash a couple times, then shut off

most samsungs have pull-up resistors, so backlights come on when cable is unhooked.

[edugimeno]

Re: Bl in Samsung will flash a couple times, then shut off

Ok I opened this TV today. What an old set inside!! (2008 I believe)
The PS board is huge. The ps board itself has connectors shaped in the edge of the board to connect to the backlighting at one side (see pics)
Im wondering now, is this TV LED or CFL?
Anyway I unplugged the main-to-ps cable and the BL didn't turn on.
So I put it back in and turned it on again and pulled the main cable immediatly out, and the on-off cycle happened too.

Do you believe this TV is repairable?

Thanks

[nomoresonys]

Re: Bl in Samsung will flash a couple times, then shut off

appears to be cffl, need to be very careful BIG DEADLY VOLTAGE in that socket area where they plug in when powered. Are you sure about that model number?

[nomoresonys]

Re: Bl in Samsung will flash a couple times, then shut off

I would start with the easier stuff, check the solder joints, check the diodes and resistors, check transistors for shorts, the caps are 14 years old could be one or more are bad. maybe hit the electrolytic caps first with a hairdryer see if it turns on or theres any change if only for a bit, start with the ones by the connector then the others, no joy hit the other ceramic caps with hairdryer.

[edugimeno]

Re: Bl in Samsung will flash a couple times, then shut off

Ok, yes Im aware of the risk in these PS's, I never touch them while plugged into mains and I always discharge caps after power off if I need to touch them.

Yes if you check the 2nd picture you will see the plugs-to-BL while it was still on, but the board was correctly sitted into the BL plugs when I opened it, there was a bunch of screws holdnig it in place

I will check those caps and Q's and see what I can get, thanks

I've never had a CFL BL Tv for repair, are they worth if by any chance the board is fine but the tubes are blown? Do they still sell these tubes (and at a reasonable price)? This TV doesn't even pick the HD DVB channels (DVB-T2)

Or maybe it's not common that the issue is in the tubes and usually its the electronics?

Thanks!

[nomoresonys]

Re: Bl in Samsung will flash a couple times, then shut off

well probably not worth messing with, might be pretty hard finding the tubes if they're bad and probably nobody wants to buy a ccfl anymore but personally I think they are much more reliable than the newer led panels that seem to constantly be shorting out. To me my old 40 inch ln model always looked great with pretty good darks and very nice whites, that's what I always check first, really surprised at a lot of the more costly tvs and how shitty and dingy the whites look, no matter how you adjust them.