Samsung LN55C650L1FXZA No Backlight

[Thorsbolt]

I have a 55" LED Samsung I brought home from work to fix for an old folks home because the residents watch it regularly. It has sound but no picture unless a flashlight is shined into the screen. I immediately thought the invertor board after a little testing. I replaced this but got the same results from the screen. Capacitors look good without testing. I replaced bad caps on a Samsung before that were bulging. I'm just starting to fix TV's as a hobby, I've fixed two now, but this one is eluding me. What should I try next. Attached are photos of the power board, video board, and invertor board.

[Peter Chiu]

Re: Samsung LN55C650L1FXZA No Backlight

First: solder T1801s and T1802s ,see, if they have any bad connections at the two HV Transformers.
second: Use neon light hold one side , and close to that two HV Transformers see if ever light up. Have your mother-in-low hold for you, and U turn on the power switch.
If it blinks is the screen's CCFL lamp.
If not,change BN44-00342B Power Supply.
If neon light drop down by shock, change the .........no.....no.... change the HV Transformer.

[nicholas1110]

Re: Samsung LN55C650L1FXZA No Backlight

Hello,

I have repaired many of these power supplies. First make sure your main board is good, check for the bl_on voltage on the power supply. If you have proper bl_on signal, the it will most likely be the ci818 capacitor just above the fuse near the middle of the board. Hope this help.

[GARMANDOKEL]

Re: Samsung LN55C650L1FXZA No Backlight

I have a 55" LED Samsung I brought home from work to fix for an old folks home because the residents watch it regularly. It has sound but no picture unless a flashlight is shined into the screen. I immediately thought the invertor board after a little testing. I replaced this but got the same results from the screen. Capacitors look good without testing. I replaced bad caps on a Samsung before that were bulging. I'm just starting to fix TV's as a hobby, I've fixed two now, but this one is eluding me. What should I try next. Attached are photos of the power board, video board, and invertor board.

Did you fix your tv? I have a Samsung model LN46D550 with the same issue, I have replaced the inverter board and it's still the same.

[budm]

Re: Samsung LN55C650L1FXZA No Backlight

Hello,

I have repaired many of these power supplies. First make sure your main board is good, check for the bl_on voltage on the power supply. If you have proper bl_on signal, the it will most likely be the ci818 capacitor just above the fuse near the middle of the board. Hope this help.

+1, you can see the cap (2W 474K marking on top) is bulging on the sides. It is Polypropylene type for high pulse current. I replaced many of these caps also. It is coupling cap fro driving the inverter transformers.
Remove it and check its capacitance (0.47uF 450V cap).

[Thorsbolt]

Re: Samsung LN55C650L1FXZA No Backlight

Thanks Nicholas and Budm, I'll try testing and likely replacing that cap. I can't believe I didn't notice it before. Sometimes you just need a second pair of eyes on things. I'll post an update regardless of outcome.

[budm]

Re: Samsung LN55C650L1FXZA No Backlight

http://www.digikey.com/product-detai...607-ND/3844530

[Thorsbolt]

Re: Samsung LN55C650L1FXZA No Backlight

Does it need to be a Polyfilm box capacitor or will any 0.47uF 450V +/- 10% work? I've got around a .69" lead spacing and I can find them close but I'll have to make one work.

[Thorsbolt]

Re: Samsung LN55C650L1FXZA No Backlight

I've got it de-soldered and checking a specialty electronics store tomorrow. I bought my last capacitors there.

[budm]

Re: Samsung LN55C650L1FXZA No Backlight

It is not just standard poly film, it is high pulse handling type cap, regular poly will not last in that circuit.
The body type does not matter, the application of the cap is made for is important.

[Thorsbolt]

Re: Samsung LN55C650L1FXZA No Backlight

Thanks again for everyone's help. Soldered the new capacitor in this morning and if fired right up. So many people fix their problems with your help and never reply that it's solved. I think that's ridiculous. So thanks again.

[Thorsbolt]

Re: Samsung LN55C650L1FXZA No Backlight

Also I Guess I have a good spare invertor board for one of these sets. Good for testing against.

[budm]

Re: Samsung LN55C650L1FXZA No Backlight

Thanks for the follow-up on the repair.

[Thorsbolt]

Re: Samsung LN55C650L1FXZA No Backlight

No problem, it should be a requirement.