Intermittent blank screen on a Samsung PN64D7000 plasma

[Cannikin]

Hey guys,

So I've got an interesting one. Over the past six months or so, on a random day, after a couple hours of use, my screen would go black and the TV would stop responding to the remote. Pressing any key would just cause the LED at the lower left to blink rapidly, but nothing would respond, not even power off. The only solution I'd found was to unplug from the wall for a couple of hours. Plug back and it would be fine, sometimes for weeks or months. This has happened intermittently.

Yesterday the screen went blank when I tried to turn it on for the first time in the evening and no amount of unplugging would bring it back to life. When plugging it back in the LED would blink 6 times and then nothing. On the back of the set the logic board has a green LED that would blink off every couple of seconds. That's it.

So this morning I laid it on the floor and took off the back. Time to test some voltages. Va measured just about 0 volts (like 20 mV, maybe). Vs measured about 5V when first plugged in, the slowly rose to 7V after a minute or so. I figured the power board was bad. Just to check I unplugged all connectors out to other boards and plugged the set back in. Now I got 0V for Va and Vs.

Here's the fun part. Plugged the other boards back in, plugged in the power, and everything started up like normal. This was all within the timespan of a couple of minutes, from unplugging the boards and testing to plugging them back in and testing.

So I don't know if I just went back into my "unplug it for a couple of hours" mode and now it'll work again for a few days...the set has been unplugged all night and this morning still wasn't turning on, whereas normally unplugging for an hour or two would do the trick.

Anyone have any ideas? Is this obviously a power board problem and I can just replace that and be good to go? I don't see any bulging caps or obvious scorch marks. All the ICs down the Y-buffer look good. Three of the four big torus inductors/transformers on the power board have black goop in the middle, but the other has white...don't know if that's a clue or they just used different goop for those.

Thanks for any help!
Rob

Pictures

Lighting isn't the best but I can reshoot any if needed.

Overview: http://ridingtheclutch.com.s3.amazon...images/all.jpg
Power: http://ridingtheclutch.com.s3.amazon...ages/power.jpg
Logic: http://ridingtheclutch.com.s3.amazon...ages/logic.jpg
X Sustain: http://ridingtheclutch.com.s3.amazon.../x-sustain.jpg
Y Sustain: http://ridingtheclutch.com.s3.amazon.../y-sustain.jpg
Y Buffer Top: http://ridingtheclutch.com.s3.amazon...buffer-top.jpg
Y Buffer Bottom: http://ridingtheclutch.com.s3.amazon...fer-bottom.jpg

[davep911]

Re: Intermittent blank screen on a Samsung PN64D7000 plasma

My situation is the same as yours on my 60" except mine just started shutting off a few days ago and quickly got worse. I can tell you if you unplug the x and y boards the power supply is programmed not to power up. I also don't see any bad caps and have the same power supply.

[selldoor]

Re: Intermittent blank screen on a Samsung PN64D7000 plasma

We ask that pictures are posted using manage attachments - jpg less then 3mb are good.
Offsite ones disappear so the thread makes no sense and no help to future enquirers.

Have you tried redoing what you did when it came on :-
Time to test some voltages. Va measured just about 0 volts (like 20 mV, maybe). Vs measured about 5V when first plugged in, the slowly rose to 7V after a minute or so. I figured the power board was bad. Just to check I unplugged all connectors out to other boards and plugged the set back in. Now I got 0V for Va and Vs.

[Cannikin]

Re: Intermittent blank screen on a Samsung PN64D7000 plasma

We ask that pictures are posted using manage attachments - jpg less then 3mb are good.
Offsite ones disappear so the thread makes no sense and no help to future enquirers.

Sorry about that. Attached!

[Cannikin]

Re: Intermittent blank screen on a Samsung PN64D7000 plasma

Have you tried redoing what you did when it came on :-.

Yep, once the set came back on the voltages measured within 1V of the reference on the panel. 217V for Va (reference 217V) and 56V for Vs (reference 55V).

[selldoor]

Re: Intermittent blank screen on a Samsung PN64D7000 plasma

Sorry I meant unplugging all connectors and boards -then reconnecting it all again
maybe just a glitchy connector

[Cannikin]

Re: Intermittent blank screen on a Samsung PN64D7000 plasma

Sorry I meant unplugging all connectors and boards -then reconnecting it all again
maybe just a glitchy connector

Is that a common problem? The connectors seemed very solid and were plugged in fully. And I hadn't touched those connections before today...seems odd that they would fix and unfix themselves randomly over the past few months, no?

It felt to me like it would in some way be heat or capacitance related since leaving the set unplugged for a while is what seemed to fix everything. If it was a digital component problem I would think it would just be broken and that's it, but this comes and goes so it feels like an analog issue.

But I'm by no means a professional, just a gut feeling.

[catman60]

Re: Intermittent blank screen on a Samsung PN64D7000 plasma

I have the same issue. Samsung replaced my screen, x and y boards and the power supply. It worked for about 3 weeks then started doing it again. If I unplug the y board I get sound and it appears to stay on. But this was just replaced. I have 2 buffers, could this be an issue.

[jl449]

Re: Intermittent blank screen on a Samsung PN64D7000 plasma

Cannikin... did you figure the intermittent problem? I'm experiencing the same thing. Few days ago screen went out and only green led in the back flashing. The front red led would blink when I press the on/off button or any of the buttons but blank screen. No splash screen or menu screen.
Unplugged it overnight and next day late afternoon.. powered it up and it all works now. Took the back panel off ...
I was going to order the Y and X sustaining boards and replace it. I don't want to remount it just for it to go out again.

[jl449]

Re: Intermittent blank screen on a Samsung PN64D7000 plasma

Follow up on my blank screen problem...

The TV finally went out... Blank screen.
I ordered a Y main board since I unplug the comm ribbon cable on the Y main board and the TV started to respond very different. It would now turn on/off but still black screen. Ordered a Y main from ShopJimmy.com. Installed it and it didn't work!!
I then search Ebay.. and found all the board except Y main and Y Up/low buffer. Came out of a PN64D8000 series but all the boards match my PN64D7000 except for the mother board. Installed all boards - X and X buffer, T conn, and power supply board. -- no luck. bought 2 y buffer boards and installed -- no luck.
Then ordered a Main board (7000 series) no luck.
Gave up. I spent over $290 worth of boards and no luck. Called a local TV repair man - Kim's TV repair. Before he picked it up I put all the original boards back on and marked them. He fixed the TV!! I asked him what was wrong and he said Y main board was bad!!!! He charged me $320.
I return the Y main, Y buffers and main board. At least I recovered most of the funds.
I removed the back cover and inspected the boards. Sure enough the Y main board was changed as it didn't have my marks. All other boards were original board.
Now since I have a PNxxD8000 motherboard I decided to install it. Bammm it worked! Connected to the net and it updated to the latest firmware. I HAVE ARC now which the 7000 lacked.
This should have been a $80 fix but I guess I got a bad Y main board from Shopjimmy.
TV working great and it's now a 8000 series w/ARC.. Total cost 450 bucks.

[nortondlcl]

Re: Intermittent blank screen on a Samsung PN64D7000 plasma

I'm having the same problem you were having with my PN64D7000 and I can't find replacement motherboard, PN648000 motherboard worked ?