Mulja tv repair portal
Equipment Repairs => LCD TV forum => Topic started by: Nix125 on August 15, 2019,16:16:45
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Good afternoon all hope someone can help,
One evening a week ago Our samsung TV screen suddenly went blank but audio was still working. Left for a while then turn off/on power to see it this resolved the issue but issue still persists. Input is not the issue as menu screen is not visible either. Did the flashlight test which failed also. Audio still works but no led back light or video display.
Please see attachment for picture of the tcon, power board and main board. Before I start randomly changing boards, ect. When powering up the front red LED flashes around 7 times. Can anyone advise on how and what to test next?
Kind regards
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One of the common failures is of the LED strips inside the TV which provide the back light.
do a general search Samsung led backlight will be some utube stuff should point you the right way
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I've looked into that and can use 4 x 9 volt batteries to test the 12 bulb led strips but it failed the flashlight test so wondering if it's a psu fault?
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could be psu is there a number on the pcb ?
if the voltages are marked would be easy to test
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Hi fix2003 thanks for the reply. Theres an attachment on the post for the pcb.
https://quuq.org/forum/index.php?action=dlattach;topic=10685.0;attach=5226
Doesn't look very well labelled. You can see the set of leads that go to the main board and the other to the leds. I'm hoping it's the pcb as they are pretty cheap to buy. Any advise on testing? Have you had encountered this issue where you have sound but no led back lights and fails the flashlight test?
King regards
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Hi Nix,
With the back off you can usually see if the back lights are working, light leak out making it obvious. If not, but there's sound, it's 99% that there are duff Leds in the back light array.
With the screen off you can check each Led with a 9v battery and 1k series resistance (in case they're 6v leds), but only by flipping the lenses off, as otherwise it's difficult to get contact through the strip insulation.
Otherwise, China does a good cheap tester where you can check a single diode or an entire string without needing bother with voltage or current, the device indicating what voltage Led fitted. Should you have an O/C Led, you'll need take the lenses off to find which one it is unless there are burn marks on the strip.
Been there - Good luck - Chris.
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Thanks for the info turnip much appreciated.
LEDs are definitely not producing any light. If one goes does that effect all of the LEDs hence why having to test strips? Why would the flashlight test fail is this because you cannot always see with a flashlight in the dark?
Kind regards
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Hi Nix,
Strips are in series, sometimes connected direct to a two lead feed, or in other sets with multi leads, strips are again in series.
With just one duff Led - The inverter can sense either an O/C Led or a shorted one. Admit in some cases 6 can go S/C before the inverter susses and cuts the power.
With an O/C led (Usually poor initial soldering which can lead to a track burn) the inverter cuts straight away.
Hence it's useful to have a tester to check each strip individually.
Wouldn't worry about the flashlight test as your Leds aren't alight, proving the issue - Chris.
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so received a second hand tcom board today that I purchased from ebay for 11 quid delivered. When I connected it up and turned on the power three blue leds lite up then a noise that sounded like a hdd booting could he heard and the tv is now working perfectly. Didn't realise that the board had lights as the broken one none lit up.
Kind regards
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If all are lit, T-con is OK. If any are out, could be the T-con or panel.
Also with most Samsungs, disconnecting the main from the power supply should result in backlights working. If so, main board is faulty. If not then it could be power supply or backlights faulty. Bruce
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I don't think you read the above correctly this issue was fixed with a second hand tcom board
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No, I read it right. Just making observations that might be useful to others in the same predicament.