Samsung UN55D6450 turns itself off and on endlessly, no blinks

[withalligators]

That's the simple gist of it, my friend has a Sammy UN55D6450 that when plugged in turns itself on (relay clicks, backlight turns on) and then instantly shuts itself off. A few seconds later it repeats this process. He'll let me have it for 250. What do we think? Seems fixable. Main board? I haven't opened it or anything.
Cheers,
Alex

[tom66]

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

I'd be thinking main board or t-con, is picture visible just as it cuts off? Could be shorted LED strip too.

[withalligators]

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

It shuts off too quickly. Granted, I didn't have a video source hooked up, but sammys display a logo when they boot on, right? Anyway, this sounds fixable to me. Do you much smarter guys concur? I can pick up today or I have to wait a week.

Cheers,
Alex

[capkid]

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

It sounds fixable, and I'd be thinking main board, also. I'd probably buy it, although I'd have a hard time paying $250 (just my cheapness with regard to non-necessities ). It looks like a nice TV.

[withalligators]

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

OK guys, I brought it home. When you first plug it in, the relay clicks and it turns itself on, and a quick Samsung Smart TV logo appears for less then a second and then it shuts off. A few seconds later the relay clicks again and the screen flashes on and then off instantly, with no logo. The top of the screen is also brighter than the bottom as if that edge is lighting but the bottom isn't. Pressing the power button does nothing. It will continue this cycle until you unplug it. At which point the relay will click on and off a few more times, but at a progressively slower rate. Any new ideas? I'm still thinking main but wouldn't be surprised if it were a component on the power board. would photos of any of these boards help?
Cheers,
Alex

[capkid]

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

Yes, clear pics of the circuit board layout and what you see onscreen would be helpful.

[johnboy1313]

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

The top of the screen is also brighter than the bottom as if that edge is lighting but the bottom isn't.

Could be shorted LED strip too.

This is where I would start. Try unplugging the LED strips one at a time to see if it will stay on. If it shuts off, plug that one back in and unplug the next one.

[withalligators]

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

The whole shebang:

The main:

The power board:

TCON:

[withalligators]

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

How does one get at the LED strips? When the logo appears, it seems uniform. It's every flash after that where the backlighting seems uneven. Also, while the red LED seems to just turn off and on inverse to whether the screen is off or on, it blinks twice after each relay click after you unplug it.

[aaronwt6]

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

It apprears to me that there are tow cables at the top of the power supply going to the LED strips. I'd start by powering the set up with one then the other unplugged (ones at a time). If it powers up with either or unplugged then its going to be the LEDs.

[withalligators]

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

I tried that, the relay clicked, but it wouldn't turn on with either unplugged

[withalligators]

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

Yoicks, I can't find replacement main board for this anywhere except TVserviceparts, where they want 175. Anyone have any leads? It's p/n BN94-04359V. Shopjimmy lists these as substitute parts:
BN94-04357J
BN94-04359U
BN94-05038U
BN94-04359W
BN94-05038N
BN94-05038R
BN94-05038Y

[withalligators]

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

Ok, I'm putting this on the backburner until I get a notification from ebay that one of these boards has become available. If it works, I'll update so there is a thread out there in case someone else encounters the same problem. If it doesn't, I'll go the TCON route.

[tom66]

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

You can also set a notifier up with ShopJimmy.

[capkid]

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

I also like to get main boards from Tristate Module, since they offer a 6-month warranty. I almost had to return a main board before I figured out that an obscure firmware update was necessary along with the main board replacement, and Tristate didn't hesitate to take back the board when I called them. So, I'd keep an eye out for an available board on their site.

[withalligators]

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

Found a main for 80, disappointingly didn't do the trick. I looked more closely at the screen as it turned on and off, and the bottom edge LED lights may not be turning on. Is there a way to test this better?

Next time I go home, I'll take video in a dark room.

[withalligators]

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

Yeah, the bottom 1/4 or so of the screen is dark. It's *really* hard to tell in this video, but here it is:
http://s294.photobucket.com/user/wit...07841.mp4.html
Is there any way to test the pins to see if its actually the LED before I open up the panel?
Thanks,
Alex

[tom66]

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

Any way you can get a full lit screen, maybe full white?

[freakaftr8]

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

You cannot ohm an led strip. I'm learning about this more and more. The led tv incorporates a "balancer" to judge if the led strips are working optimal or not. What you need.ro do is get the service manual and find what voltages are on the balancer pins and led controller ic but im betting in you having some internal led error.

[RJARRRPCGP]

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

It may be a primary issue.