Samsung PN50C430 A1DXZA - Intermittent Vertical Bar

[doublfelix]

Hi folks,

Shortly after it turned 4 years old, my Samsung PN50C430 (A1DXZA - Version NY02) developed a vertical strip of pixels that ranges from working fine, to a sort of dancing rainbow type thing, to a black strip with one or more single color stripes going through it (a picture of the symptom is attached). I heard from two sources that it is likely a buffer issue, but that the buffer boards on this model are somehow bonded to the plasma panel, and thus can't be (easily at least) replaced independently from the panel.

The display sat in its box since I got a new TV (last July) until a week ago. Having nothing to lose, my brother and I tried disconnecting and re-seating all of the connections to the E and F buffer boards, and using De-oxit gold on the connectors where the ribbon cables attach. Lo and behold the problem went away, and it stayed away for somewhere between 1 and 2 hours of operation before it came back.

Two questions: 1) Any ideas why my fix actually worked for a little while?
2) Could this symptom be caused by something upstream of the buffers, and if not am I completely out of luck as far as trying to identify and repair or replace a bad IC if the boards themselves truly can't be replaced?

Thanks in advance!

[doublfelix]

Re: Samsung PN50C430 A1DXZA - Intermittent Vertical Bar

A quick update. I had wondered whether the temporary disappearance of the vertical bar was actually due to the Deoxit, or just a result of being unplugged for months. I tried leaving the tv unplugged overnight, and turned it on for a few minutes today without the problem resurfacing. If I leave the television plugged in but use the remote to power it off, the vertical bar returns immediately after turning it back on. Not sure if this behavior helps with the diagnosis at all, but it at least seems to render the tv usable for short periods.

[ljintexas]

Re: Samsung PN50C430 A1DXZA - Intermittent Vertical Bar

Logic board or lower scan buffer could be at fault.

[doublfelix]

Re: Samsung PN50C430 A1DXZA - Intermittent Vertical Bar

I am planning to take the back panel off this weekend so I can post a picture of the boards. I downloaded the Fast Track guide for this model, but am unclear whether the video problem troubleshooting in the manual can actually tell me anything further than what I already know? I have a basic DMM, and can get access to a nicer one (with diode mode, etc.) if measurements would be useful for diagnosis.

[Shinju]

Re: Samsung PN50C430 A1DXZA - Intermittent Vertical Bar

might be a dirty buffer ribbon cable, I would track down and localize the area that is tied with that ribbon cable and remove it and clean it and re seat it.

I have saved a few Samsung and Panasonic plasma panels this way Being that yours is coming and going I would suspect a dirty connection..

Make sure to do this while the TV is off and make sure to reseat the cable straight.

[doublfelix]

Re: Samsung PN50C430 A1DXZA - Intermittent Vertical Bar

Thanks for the reply Shinju! While I didn't double check this the last time I had the back panel off, I'm pretty sure the connections from the buffers to the panel are bonded on this set (from reading other threads, it seems like more of the infamous "tab bonds") so cleaning and reseating those connections won't be possible. I will check again though. I'm currently thinking of going with the following approach if it makes sense.

1. Run logic board test pattern from service menu while tv is operating properly
2. Watch some tv until the problem shows up, then run the test pattern again

Hopefully this might help determine whether the logic board or buffer is at fault, since it looks like I can get a replacement logic board for ~$20.

If this points towards the buffer I'll test with DMM, though the fact that it works fine for a while still has me kind of stumped.

If the issue is heat related I might try removing the speaker that sits over the top of the heat sink for the offending buffer board to better dissipate heat...or there is also the thermal pad fix for tab bonds.

Seems like I'll mostly just fiddle around with it when I have some time this weekend, but let me know if I've incorporated any bad logic in how I'm proposing to investigate.

[doublfelix]

Re: Samsung PN50C430 A1DXZA - Intermittent Vertical Bar

I was able to mess around with the television a bit this weekend. Running the patterns was amusing if only because I've never been in the service menu before.

1. The logic board test patterns were good when the picture was good, but when the vertical bar showed up, it showed up in the patterns as well. More so when the patterns incorporated white (i.e. the solid green, red, and blue patterns I didn't see the fuzzy bar at all, though it tends to come and go and I didn't dwell on any particular pattern for too long). As I kind of suspected before though, I don't think this tells me anything as far as logic board vs. buffer being faulty.

2. Confirmed the following - the vertical line behavior occurs after the set has been plugged in for a certain period of time. It does not need to be powered on. For example, last weekend I plugged the tv in and watched about 2 hours of programming before the symptom showed up. I unplugged the set, and then plugged it back in four days later - the symptom showed up after 30 minutes of programming. Unplugged it, plugged it back in two days later (yesterday) and watched 45 minutes with no symptoms. Left it plugged in overnight, and the problem showed as soon as I turned on the TV today.

3. Took the back off the tv today and took some pictures. I was going to inspect the buffer boards further (E and F boards per Samsung) but I can't for the life of me figure out how to get the last bracket/heat sink off of them (they are along the bottom of the panel in the photos). It almost looks like you have to get underneath the aluminum tray that all of the boards are attached to in order to remove it. Consequently I couldn't even inspect the actual chips on those address boards.

Just out of curiosity, does anyone know if the logic board and/or buffer boards see some sort of voltage when in standby, since apparently being in standby still aggravates the picture problem? The logic board gets power directly from SMPS (looks like Vs?) while the buffers get power from the Y-main (looks like Va?). My first thought was that since it took a while for the problem to show up it could be a thermal thing (bad solder joint, etc.) but the standby thing has me questioning that...is it worth checking to see if one of the voltages is straying?

[Shinju]

Re: Samsung PN50C430 A1DXZA - Intermittent Vertical Bar

you will have to find a way to get to those bottom buffers and investigate those connections.

[doublfelix]

Re: Samsung PN50C430 A1DXZA - Intermittent Vertical Bar

After figuring out how to get better results from the search function, it looks like this is a somewhat common problem among this generation of Samsung 720p sets - effectively a panel failure due to the E and F boards being bonded to the panel. Since I can get the set to work properly for a little while, I'll keep experimenting with ways to try and extend that operating period and post back if I have any success.

[tom66]

Re: Samsung PN50C430 A1DXZA - Intermittent Vertical Bar

You may be able to re-bond that connector by heating it up gently. The address drivers have few connections, but they are soldered on the opposite side, so it's kind of tricky.

[doublfelix]

Re: Samsung PN50C430 A1DXZA - Intermittent Vertical Bar

Ok, you guys convinced me to keep trying. TV will go back on the operating table (hopefully) this weekend, though I'm trying to find a new one (operating table that is) where I don't have to worry about the kids or dogs accidentally getting into things. Based on what I saw with the back panel off before, and what I can glean from this video, I may have to pull the panel out of the frame in order to fully see if that last metal strip covering the address boards is indeed attached on the front (and if not, why the heck I haven't been able to remove it so far). Update to come.

[doublfelix]

Re: Samsung PN50C430 A1DXZA - Intermittent Vertical Bar

Just to potentially help people out in the future - I did not have to open the TV up again, but the problem has been fixed so far. When I had the back panel off to shoot the original photos, and I was trying to access the E and F buffer boards, I noticed a common mounting/grounding screw (highlighted in the red box) where the two boards meet each other in between the cable that I presume supplies power from the E board to the F board. This screw was torqued down really tight, to the point where it appeared to be flexing the actual E and F PCBs. I backed this screw out completely, then tightened it just enough to make a solid contact for grounding purposes, but not enough to flex the board. The vertical bar showed up maybe once or twice when I first turned the tv on after loosening that screw, then went away and hasn't come back in nearly a month of semi-regular operation.