Samsung UN55D6450 turns itself off and on endlessly, no blinks

[withalligators]

Re: Samsung UN55D6450 turns itself off and on endlessly, no blinks

After reading up on Samsung cap and PSU failure, this error sounds like it could be in the PSU. Rather than drop a 100 bucks on this board though and before I crack open the panel itself, I'd love to see if I could try and evaluate this on the component level. Unfortunately, this puts me in way over my head. I've got the schematic, but am fairly lost as to how to read or interpret it to any degree that will help me test anything out.

Do any of you delightful gents want to point out some pins or something I can test to determine if the LEDs have failed or if it's on the board somewhere?

Also, no caps appear bulged, all PSU fuses test fine, and the pico fuse on the TCON is ok as well.

Thanks all,
Alex

[tibimakai]

Re: Samsung UN55D6450 turns itself off and on endlessly, no blinks

This is just an idea, may not be your issue.
I would disconnect the ribbons going to the panel from the T-con, to see if it stays on.
I have a UN46D6420 which seems like it has a bad panel. With one ribbon connected, I have half screen working great, with both connected, I have only backlight.
I have repaired a Sony which did almost as yours, but stayed on almost 20 sec. and it ended up being the LED driver board which was a separate board. On yours is most likely is build in in the power supply board. Maybe those four yellow transformers.

[withalligators]

Re: Samsung UN55D6450 turns itself off and on endlessly, no blinks

Tried it, nothing changed. Thanks though!

[withalligators]

Re: Samsung UN55D6450 turns itself off and on endlessly, no blinks

OK, I have zero idea what I'm doing, but I played around testing some points on the PSU. I set my DMM on 1000VDC, put the black prong on a chassis ground, and touched the red to a number of places. All directions are facing the back of the TV.

All 4 of the yellow transformers (L-R L9451, L9351, L9251, L9151) put out roughly the same numbers between cycling on and off (125ishV to 90ishV) on both legs. The long caps directly above each transformer say something when tested one the left leg of each. The three on the right (L-R C9355, C9255, C9155) put out the same numbers 160ishV to 110ishV, while the one on the left (C9455) puts out 260ishV to 130ishV. Above that, there are three white boxes (capacitors? They're marked "C") which mirror the issue when tested on the left leg of each. The three on the right (L-R C9359, C9259, C9159) run about 160ishV to 110ishV while the one on the left (C9459) runs about 270ishV to 130ishV.



Does this point towards anything?

Thanks,
Alex

[withalligators]

Re: Samsung UN55D6450 turns itself off and on endlessly, no blinks

Any ideas, guys? I don't have to be in the field again til Tuesday, so I can put some time into this.

[tom66]

Re: Samsung UN55D6450 turns itself off and on endlessly, no blinks

The one on the right makes me think you have an open circuit LED string; I'll bet that's causing your problem. The number of these LED sets with failed LED strings is crazy. So many going bad because one LED goes bad.

[withalligators]

Re: Samsung UN55D6450 turns itself off and on endlessly, no blinks

So I have to go into the panel, huh? That looks awful. It seems to be held together with tape in such a way that it'll be hard to get back together and fragile as hell once it's apart.

[tom66]

Re: Samsung UN55D6450 turns itself off and on endlessly, no blinks

Just as a test, is it perhaps possible to swap the output of each? Are there four separate connectors for each output to the panel or just one?

[withalligators]

Re: Samsung UN55D6450 turns itself off and on endlessly, no blinks

Unfortunately, there are two plugs, but each has a different number of pins/prongs.

[withalligators]

Re: Samsung UN55D6450 turns itself off and on endlessly, no blinks

Before I open this panel, let me throw a few things out there that makes me think maybe it's the PS board.
I can't turn it off, once I plug it in, it just cycles on and off endlessly. Also, everytime it does so, the relay clicks. After you pull the plug the relay keeps clicking, but at a progressively slower pace, until it "runs out of steam". If this is suspect, I can post a video.
Still think it's an LED strip? Please say it's just some caps or something.
Thanks,
Alex

[tibimakai]

Re: Samsung UN55D6450 turns itself off and on endlessly, no blinks

It's not a big deal to open the panel. I wouldn't even open it up completely, just lift it a bit and then turn it on, to see what is going on with the LEDs.

[withalligators]

Re: Samsung UN55D6450 turns itself off and on endlessly, no blinks

From the bottom? I see a few access plates that have screws but I assumed they opened to get to the tab bonds. If not, how does one open this panel up? Do I cut the black adhesive material holding it together from behind?

Sorry if I seem reticent. I've cracked an LCD panel before putting it back together so I'm pretty nervous about doing it.

[tom66]

Re: Samsung UN55D6450 turns itself off and on endlessly, no blinks

You can most likely just take the front plastic off and metal frame, then try looking under the panel carefully by lifting it on the edge. Don't need to lift it out completely. You need a large flat surface like a workbench or bed.

[withalligators]

Re: Samsung UN55D6450 turns itself off and on endlessly, no blinks

No, this one is sort of a sealed unit, unlike the other "fatter" panels I've been in. Once you get down to the bare panel, instead of having a metal frame that you can unscrew to reveal the LCD sheet, then diffusers, then the bulbs there what may be a metal frame, but it is sealed to the panel with adhesive backed black material. Almost like a heavy duty tape.

[johnboy1313]

Re: Samsung UN55D6450 turns itself off and on endlessly, no blinks

withalligators, did you ever get this one sorted? I just brought home the UN55D6420 with a BN94-05038R main board with a smashed screen. I've unplugged the LCD from the T-Con and the set still powers on and off with the power button, including the backlights still light. I still have voltage at the T-Con as well. It appears that this set still works, minus the LCD. I'm more than willing to perform surgery on this panel and report back if that would encourage you to attempt the fix.

[mmartell]

Re: Samsung UN55D6450 turns itself off and on endlessly, no blinks

@withalligators as per a service leaflet posted by tom66 in another thread there is a way to test the individual strips and there are access holes for that reason. Will post link shortly.

I have a UN55D6000 which won't turn on and am troubleshooting it atm in the other thread.

Between you, me and johnboy i think we should be able to fix one or two of these sets anyway.

[mmartell]

Re: Samsung UN55D6450 turns itself off and on endlessly, no blinks

Btw do either of you have advice on how to remove the LVDS cable ?

[mmartell]

Re: Samsung UN55D6450 turns itself off and on endlessly, no blinks

And here's the thread. The pdf from tom66 is in post#6.

https://www.badcaps.net/forum/showthread.php?t=34566

[splitcrete]

Re: Samsung UN55D6450 turns itself off and on endlessly, no blinks

You paid way to much . The tv was broken . I always tell the seller if you think its an easy fix then you fix it. Then the price comes right down. There is always a tv some where needed to be fixed. Good luck

[mmartell]

Re: Samsung UN55D6450 turns itself off and on endlessly, no blinks

I paid $200 for a 60" Kuro that cost $40 to repair and is now hanging on my wall rwplacing a 43" Pioneer that cost 10x as much. I think I stole that television from those poor people!

I paid $150 for the 55" D6000 referenced in this thread. Repair cost yet to be deternined. I think I could replace every board in it if need be and still get my money back.

I bought a 720p Samsung plasma for $40 that is awaiting parts. Now THAT tv I may have paid too much for lol but that's just because the hobby is addidctive and I was dry atm

So you see it's all relative.