Samsung LN-T3242H black screen failure - flicker or DOA

[dcubed123]

I have an 'old' Samsung LN-T3242H LCD TV that occasionally works fine for an hour or more. However, most of the time it does not work. When it does not work, it fails in one of two ways.

1) It powers on and never shows any lighted images.
2) It powers on, shows a normal image, then after 10-20 seconds, the whole screen starts to flicker, starting at a high frequency of flicker, with a continuously lowering frequency of flicker, and always ends dark. If the flicker failure mode occurs, it always shows the frequency shift.

The audio continues to work. I also believe that all other controls work, but I can't tell since the screen is blank.

My guess (uneducated) is the inverter board, but I don't want to arbitrarily start replacing parts.

I have read another long thread in this forum on a similar failure, but it seems my flickering failure mode is unique.

Any insights/suggestions?

[budm]

Re: Samsung LN-T3242H black screen failure - flicker or DOA

https://www.badcaps.net/forum/showthread.php?t=39740
Did you open it up and inspect the boards yet?

http://s807.photobucket.com/user/bud...?sort=3&page=1

[Shinju]

Re: Samsung LN-T3242H black screen failure - flicker or DOA

I had one of these, every cap on the power supply excluding the high voltage one was popped/domed.

The TV worked amazingly enough in its badcap state but had a major screen issues, had dark spots, the left side of the screen after 2 hours would scramble like a bad tab-bond issue. I was about to scrap it prior to taking it apart only after I needed an older power supply to check a mainboard on another TV and noticed the cap issue.

I replaced them all, after that the dark spots were almost non existent and would go away 100% after 5 min of being on (damage happened due to power supply strain from the bad caps I am sure), the screen didn't scramble the left side after 2 hours anymore didn't scramble at all after.


Turned out to be a decent little 720p TV.

[dcubed123]

Re: Samsung LN-T3242H black screen failure - flicker or DOA

https://www.badcaps.net/forum/showthread.php?t=39740
Did you open it up and inspect the boards yet?

http://s807.photobucket.com/user/bud...?sort=3&page=1

Thanks for explaining that photos would be very helpful. I have done the best I can with my camera. If I need to shoot anything better or anything that is missing, let me know. I really don't what to inspect first.

[dcubed123]

Re: Samsung LN-T3242H black screen failure - flicker or DOA

more pics

[dcubed123]

Re: Samsung LN-T3242H black screen failure - flicker or DOA

I had one of these, every cap on the power supply excluding the high voltage one was popped/domed.

The TV worked amazingly enough in its badcap state but had a major screen issues, had dark spots, the left side of the screen after 2 hours would scramble like a bad tab-bond issue. I was about to scrap it prior to taking it apart only after I needed an older power supply to check a mainboard on another TV and noticed the cap issue.

I replaced them all, after that the dark spots were almost non existent and would go away 100% after 5 min of being on (damage happened due to power supply strain from the bad caps I am sure), the screen didn't scramble the left side after 2 hours anymore didn't scramble at all after.


Turned out to be a decent little 720p TV.

Thanks for posting about your experience. Your failure mode, however, seems unlike mine, so I am not sure that your solution is applicable to my problem.

[dcubed123]

Re: Samsung LN-T3242H black screen failure - flicker or DOA

I have added pics, as suggested (requested). I was hoping that my very specific failure mode would allow some of the more experienced members to shortcut my diagnosis by offering likely causes that I could investigate. Any input would be greatly appreciated.

[budm]

Re: Samsung LN-T3242H black screen failure - flicker or DOA

https://www.badcaps.net/forum/attach...5&d=1415246636
https://www.badcaps.net/forum/attach...6&d=1415246636
Way out of focus. It looks like the caps have domed tops.

[dcubed123]

Re: Samsung LN-T3242H black screen failure - flicker or DOA

https://www.badcaps.net/forum/attach...5&d=1415246636
https://www.badcaps.net/forum/attach...6&d=1415246636
Way out of focus. It looks like the caps have domed tops.

Sorry. I have two problems: no photography skills and a crappy camera. I will try to do better and upload again. Thanks for working with my images and making the suggestion on the caps.

[dcubed123]

Re: Samsung LN-T3242H black screen failure - flicker or DOA

New pics of the caps on the main? and inverter? boards. They don't look domed to me, but I welcome others' opinions.

[budm]

Re: Samsung LN-T3242H black screen failure - flicker or DOA

OK, little better pictures now and now I can see that the caps on the inverter boards do not have domed top.
What you can try is before turning on the TV, heat those caps on the inverter board with hair dyer for a few minutes, then turn on the TV and see if you can see the backlights flicker. Try looking at backlghts through the holes on the back of the LCD panel since we want to make sure the flicker is not due to the T-CON board.

[dcubed123]

Re: Samsung LN-T3242H black screen failure - flicker or DOA

Thanks for tip. I did as you suggested, but the TV powered on fine (it does this much of the time). I will retry the procedure after the TV starts failing again. I will be sure to let it cool before I try heating the caps and re-powering.

In the mean time, are there any additional improved photos that you would like to see?

[Shinju]

Re: Samsung LN-T3242H black screen failure - flicker or DOA

Might as well recap the power supply since you have it open if you havent done so already.

[dcubed123]

Re: Samsung LN-T3242H black screen failure - flicker or DOA

Might as well recap the power supply since you have it open if you havent done so already.

Should I re-cap even if they don't appear domed? Should I do both the power supply and inverter caps? Should I upgrade the caps when I replace them?

[budm]

Re: Samsung LN-T3242H black screen failure - flicker or DOA

Bad caps can look normal but can have high ESR, or lost of capacitance.

[Agent24]

Re: Samsung LN-T3242H black screen failure - flicker or DOA

If you don't have an ESR meter you can only replace them and hope it solves the problem. Since the PSU capacitors are CapXon brand (and which are quite awful in terms of quality) I would replace them anyway.

[dcubed123]

Re: Samsung LN-T3242H black screen failure - flicker or DOA

I have an interesting development. The TV failed last night right after I turned it on. Since the back is off, I hit the inverter board with the hair dryer. The screen lit up immediately and the TV stayed normal all night.

Tonight, it failed again on power up. This time, I only briefly and slightly heated the inverter board. The screen lit up, but the left side was a little dark. I used more heat and the screen became normal. It has been fine all night.

I am thinking I have a bad cap (or caps) that do not properly allow some circuit to start up. After it is (they are) heated, the start-up signal propagates properly and the TV is fine until it cools and is subjected to another re-power.

Based on the last two posts (thanks, guys) and my observation, it seems that cap replacement is the first thing I should do. Any specific recommendations on type and brand? Do I first just the inverter board caps, or do all of them?

[Agent24]

Re: Samsung LN-T3242H black screen failure - flicker or DOA

It certainly does seem to indicate that your inverter is heat sensitive. The situation you describe is classic of half-dead capacitors. Funny though, your inverter uses Rubycon which are a top notch brand and I would expect them to outlast the CapXons.

You could replace the inverter capacitors and see what happens. If the problem goes away, great. Then I would pre-emptively replace all the ones in the PSU as well.

For replacements, you are probably fine to use the same ones that were already in there - Rubycon ZLH. Make sure you get the same size\diameter and value etc.


EDIT: That said... since these are Rubycon, it's possible they are perfectly fine and you have some other heat-sensitive component on your inverter board.

[budm]

Re: Samsung LN-T3242H black screen failure - flicker or DOA

I use PANASONIC FM/FC/FR for all my repairs.
Your problem is similar to this inverter board:
https://www.badcaps.net/forum/showth...ghlight=al2416

[RJARRRPCGP]

Re: Samsung LN-T3242H black screen failure - flicker or DOA

If any "KM" caps, replace on sight! They are possibly worse than Chemicon's KZG series.
Seems that a lot of them go bad without bulging or leaking! (tendency to be xtremely out of spec, too)