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Crumbtrail TV Forums: TV Equipment: TV Repair Forum:
Samsung Plasma (PN58C8000) blank screen.

 

 


tlc
New User

Nov 13, 2017, 9:46 PM

Post #1 of 4 (8285 views)
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Samsung Plasma (PN58C8000) blank screen. Can't Post

Hi, I'm hoping for some kind help fixing my plasma.

I've tried to do some debugging based on a "fast track" document I found here: http://www.toms-service-manuals.com/?do=search&mfg=Samsung&modelsrch=pn58c8000&typekey=0&Search=Submit+Query

Then I thought I saw some heat damage on the power board and bought a new one. But that didn't fix my problem.

Symptom summary:

On power on:
1) Black screen. Red Standby LED flashes 4 times.
2) Cannot display TV Menu.
3) No power on "chime" is heard, but I had the speaker disabled because the TV was downstream of my AVR.
4) Green, LOGIC board LED flashes slowly. About every 5 seconds.
5) STBY 5V is OK.
6) PS_ON transitions from 3.3v to ~124v (instead of 0v) with power on.
7) Vs, Va, Ve, and Vsc all hit their targets briefly then fall away (fast track says this model shuts down power board on problems).
8) Cannot see test patterns when shorting pins on LOGIC board and disconnecting MAIN.


From what I've read, the POWER board behavior when X-main and Y-main are disconnected is often used to decide where to look next. But according to the fast track document, this model's POWER board shuts down when they're disconnected, too. So where do I look next?

Thank you,
tlc



tlc
New User

Nov 18, 2017, 1:35 PM

Post #2 of 4 (8234 views)
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Re: [tlc] Samsung Plasma (PN58C8000) blank screen. [In reply to] Can't Post

I think I've moved forward a step.

I tried disconnecting the ribbon cables to X-Main and Y-main instead of the power cables. When Y-Main is disconnected, the LED blinks fast instead of slow! I think this means I've narrowed it to the Y- boards.

Also, Vs, Va, Vsc, Ve are all good. VS_on is 3.2 and PS_ON is still high at 124v.

This tech bulletin describes checking for shorts around OUT_H and OUT_L. But I can't find my OUT_H and OUT_L.

Thoughts, anyone? Debugging Y-main vs Y-buffers?


jts1957
Veteran


Nov 18, 2017, 8:58 PM

Post #3 of 4 (8230 views)
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Re: [tlc] Samsung Plasma (PN58C8000) blank screen. [In reply to] Can't Post

Page 4 of the Newsletter describes how to determine when "The boards on some models may not be marked."


-------------------------
Location: Far, Far Away


tlc
New User

Nov 19, 2017, 7:15 PM

Post #4 of 4 (8223 views)
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Re: [jts1957] Samsung Plasma (PN58C8000) blank screen. [In reply to] Can't Post

Thanks. Here is the link I left out of the previous post: https://www.pcrichard.com/images/promos/3CE%20Newsletter%20March%202011.pdf

It was hard to see the traces on my Y-buffers, but I eventually did that testing and found no short there. Given that I've already bought a power board I didn't need, I'm hoping to find positive proof of a Y-Main problem, rather than mostly eliminating the Y-buffers ("There will usually be a dead short if defective.").

I've ordered a manual. Hopefully that will have more testing ideas.

Thanks again.
tlc

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