Samsung PN51F8500 - Power cycle, pixel maldischarge... HELP!

[freakaftr8]

Re: Samsung PN51F8500 - Power cycle, pixel maldischarge... HELP!

Y main writes the data to the horizontal quadrants of the screen, X main primes the panel, Bottom boards drive the information vertically that the Y main drives horizontally.

All this is done by the logic board that tells what the boards are supposed to show on the screen, via timing of the screen and pixel controls and what color to light up each pixel. Hence the term logic board it is the brain of the system that the main board drives its signal to.

All this is done by scan rate or how many times the screen flashes on and off for a write and erase cycle

[ranergeo]

Re: Samsung PN51F8500 - Power cycle, pixel maldischarge... HELP!

Well... new logic/main arrived and so I popped it in and...

(drum roll please)

No change, apart from the fact that it now doesn't (seem to) power cycle anymore. I'm still testing it, but it has gone longer than previous times.

While I was waiting for the new board to arrive, I did go into the service menu and test anything it would self-test (which was quite a lot, I must say!), and also found the panel on time... in minutes... which converted to 16.5Khrs! I guess this bad-boy was on all day (and half the night) to clock up those hours in 5 years.

I just can't shake the thought that somewhere, power isn't getting to the panel, and since it's large bunches of pixels that will suddenly light up after a moment, I'm wondering if there's a failing cap or 12 somewhere on the Y-sus... I just got an ESR meter to get better test results, so I guess I'll go back to testing; however, I must admit that I'm about ready to call it a failing panel and simply harvest the set for parts...

[freakaftr8]

Re: Samsung PN51F8500 - Power cycle, pixel maldischarge... HELP!

Fire and ice. Heat the boards, cool the boards. Only way to tell. But I thought you tried new boards?

Think your answer has been answered. 16k hours on panel. Especially with static images on the screen

[ranergeo]

Re: Samsung PN51F8500 - Power cycle, pixel maldischarge... HELP!

Yeah, I did swap out both X and Y (w/ buffers) to no effect, so I put my original ones back in.

I have a 3 hour cartoon video running right now, and it's still going strong after 2 hours. The previous best was 20 minutes, so at least I'm feeling confident I found the power cycle problem.

I'd be waving the white flag if I was seeing lines across the panel, but it's supposedly Samsung's "best" panel. Although I'm pretty sure there's a couple dead pixels, the symptoms don't easily point to a bad panel ('specially since the cartoon doesn't have any pixel problems apart from the burn in along the top, although Planet Earth playing before that suffered terribly).

*sigh*

[ranergeo]

Re: Samsung PN51F8500 - Power cycle, pixel maldischarge... HELP!

One last question I wasn't able to search out...

If I'm getting green/white sparkles on a black screen, I'd usually be looking at YFR and YRR adjustments, and although I could potentially test them (at test points on the Y-sus), I don't see any pots to adjust them at? What should I look for if I'm having what appears to be sparkles on black?

[freakaftr8]

Re: Samsung PN51F8500 - Power cycle, pixel maldischarge... HELP!

Interesting. Odd how there are no adjustment pots for these settings. Maybe YFR cama YRR are adjusted internally with firmware. In that case if the panel were aging there would be no physical adjustment to compensate.

If you want my honest opinion I think 50000 hour half life is pretty vague.

Sounds like you hit all the points on Replacement wise. You've essentially replaced every board except for the power supply Which seems to be putting out proper voltages.

[freakaftr8]

Re: Samsung PN51F8500 - Power cycle, pixel maldischarge... HELP!

Stupid question but have you tried adjusting down VS instead of up to see it the sparkles dissapear?

[ranergeo]

Re: Samsung PN51F8500 - Power cycle, pixel maldischarge... HELP!

Yup, but tried it again for the heck of it (-5/+8 on Vs) and (+/-5 on Vsc). No change in overall picture quality or sparkles.

I know I could change out the SMPS just to rule almost everything out, but since it is putting out the proper voltages, I don't see the point of it. I just hate the thought of parting out a tv that should still be working fine :-/

I wish I could find a detailed schematic of the boards so I could test them a bit better...

[Moreno83]

Re: Samsung PN51F8500 - Power cycle, pixel maldischarge... HELP!

Great effort on this tv. 16.500 hours is not THAT much? I know the latest Panasonic panels are lasting +100.000 hours.
Is it the mainboard that says the panel hours on this tv or the tv itself? What are the panel hours with the old mainboard?

You did your best. Are there any lower boards in this tv like the C boards in Panasonic's? Maybe heat up those boards and see if you notice anything.

[ranergeo]

Re: Samsung PN51F8500 - Power cycle, pixel maldischarge... HELP!

Moreno, that was my thought on the panel as well, 'specially since I just did a Sammy D550 series with 13.5Khrs on it with a bad X-main and no picture issues otherwise! Interesting enough, the F8500 hides the hours pretty well, but it was the logic/main that reported the time... in minutes (it was like 980Kmin)... which worked out to about 16.5 Khrs. (I did later find a sub-sub menu that reported hours and cycles, but it was with the new Main board, which had significantly less hours recorded)

There are similar boards along the bottom, but Samsung calls them E and F boards (left and right). I thought to add them in the harvesting, but after I finally managed to almost get down to them realized that they're integrated to the panel. Unfortunately, by the time I thought to test them I had already harvested the tv and had everything on eBay.

Thankfully, aside from the time invested (which is the hobby/fun time for me), I've already made my money back (although I was really hoping to upgrade my PN50C7000 with this one... guess I'll have to keep my eyes open for a 60 or 64 inch version

My only testing now is to see whether anyone writes me post-sale reporting any of the parts I sold causes the same problem on their t.v. Then I'll definitely know if it was a panel or not! !

[Moreno83]

Re: Samsung PN51F8500 - Power cycle, pixel maldischarge... HELP!

Ah it is a good learning experience!

I just read somewhere that 10uf caps on the y-sus are a common problem? Can you confirm you got those caps on the Ysus?

[Moreno83]

Re: Samsung PN51F8500 - Power cycle, pixel maldischarge... HELP!

Moreno, that was my thought on the panel as well, 'specially since I just did a Sammy D550 series with 13.5Khrs on it with a bad X-main and no picture issues otherwise! Interesting enough, the F8500 hides the hours pretty well, but it was the logic/main that reported the time... in minutes (it was like 980Kmin)... which worked out to about 16.5 Khrs. (I did later find a sub-sub menu that reported hours and cycles, but it was with the new Main board, which had significantly less hours recorded)

There are similar boards along the bottom, but Samsung calls them E and F boards (left and right). I thought to add them in the harvesting, but after I finally managed to almost get down to them realized that they're integrated to the panel. Unfortunately, by the time I thought to test them I had already harvested the tv and had everything on eBay.

Thankfully, aside from the time invested (which is the hobby/fun time for me), I've already made my money back (although I was really hoping to upgrade my PN50C7000 with this one... guess I'll have to keep my eyes open for a 60 or 64 inch version

My only testing now is to see whether anyone writes me post-sale reporting any of the parts I sold causes the same problem on their t.v. Then I'll definitely know if it was a panel or not! !

Maybe you bought the boards from someonbe who had the same issue.

[ranergeo]

Re: Samsung PN51F8500 - Power cycle, pixel maldischarge... HELP!

Heya Moreno, I think you're referring to the common problem with the 64" version, where the three 10uF caps on the Y-sus would dry out, go low (on their readings), and shut the set down. I did check the caps on the Y, and didn't find anything out of the ordinary with my ESR meter or my Fluke (although I did "in circuit" testing, so I was basically testing an entire circuit at a time :-/ )

There is absolutely the possibility that either the x or y I received were just as bad as the ones I had, but I've not been able to find one other occurrence on Badcaps or elsewhere where these boards (on the 51") were an issue. Plenty of shutdowns due to SMPS failure and a load of logic rebuild services, but little in the way of y or x.

Now, when I changed out the logic/main, it did fix the shutdown issue, but picture performance was exactly the same... static images seemed to be fine, cartoons seemed to be fine, but when it needed to do deep blacks and then light back up, it often liked to take it's time getting it done (sometimes slowly filling in, sometimes just all popping up at the same time, sometimes it just wasn't a problem... it's best shown in the video's of my first or second post)

Unfortunately, the SMPS has been shipped out, along with the smart remote. But at least I'll know if it's the power supply depending on the report I receive from the buyer

[ranergeo]

Re: Samsung PN51F8500 - Power cycle, pixel maldischarge... HELP!

I'll add one last video in the hopes that someone has seen this before, just in case I come across it again!

https://www.amazon.com/photos/share/...ipA1B0kRAkCTij

This was nothing more than the "no source" screen, which helped rule out source problems

[Moreno83]

Re: Samsung PN51F8500 - Power cycle, pixel maldischarge... HELP!

Ok , unlucky! Hopefully you will a good set to upgrade your current tv. Personally i would take Panasonic over Samsung. Go for a VT50 / 60 or ZT60 , really amazing tv's.

I got a VT50 , still loving it!

[SCDC3212025]

I have a Samsung 3D plasma PN51F8500AFXZA with a similar issue, black blotchy spots on the screen at start up then it diminishes to leave black pixelation all over the screen like fuzz or static similar to the above issue. Ive checked for shorted mosfets and caps on the y sustain brd and found none. Moved to checking voltages on the X sustain brd and found some voltages that meta ai says are abnormal. On the x sustain i found the VE as 100 vdc, the SVT_OUT as 75 to 85 vdc fluctuating. On the ribbon connector going to the Y sustain the XERC as 120 vdc. Meta AI says those voltages are not correct and i should look for a problem on the X sustain brd. Ive checked for shorts on the mosfets and ceramic caps and found none, the only left for me to do is look for bad solder joints and ask for help on these suspect voltage values. Also the 15 vdc is there and the power supply has the VS is 209, VA is 63 vdc, the Vscan if i recall on the Y sustain is -188.6. Can anyone verify is these X sustain readings are right or wrong and if that points to the specific issue, id appreciate it, thank you