Fixed Samsung 55" LED Series 9 based on a YouTube video that makes you go WTF?

[peteru]

I've been watching Dave and lurking for a while, but this is my first post here. I just have to post, because I want to know how this is possible...

I'll start at the beginning.

I've got an old Samsung 55" Series 9 TV, model LA55A950D1F. Besides the crappy capacitors causing the power supply to take out the backlight driver board for the local dimming LED array about 3 years into the life of the TV, it's been great. Until it got cold this year.  A couple of weeks ago, I noticed that every 8 or 10 scanlines, one scanline was completely dark on the left hand side and faded up to almost full brightness by the time it reached the right hand side of the screen. My first reaction was: "Great, that looks like a deteriorating connection on a hotbar attached flex cable!" And we all know how unrepairable that is.

Anyway, as one must do, I took it apart to see what's what. A bit of basic trouble shooting and I identified the board that seemed to control the panel and reseated all the connectors. No improvement. Took the board out, inspected cleaned and Googled the part number. Found it listed at ShopJimmy as expected. The page had this comment: IMPORTANT: Horizontal lines on the screen are virtually NEVER caused by a bad T-con board. Horizontal lines indicate a defective LCD panel (screen). Great!

I put the board back and decided to fiddle a bit with the connectors while observing what they do. I figured I might as well learn how it works. Anyway, I noticed that various combinations of partial connections on the connectors made the horizontal lines go away. I decided to Google to see if anyone has fixed a problem like this. Almost all advice out there seems to suggest that it's a faulty panel and the TV is not worth repairing. A few people suggested replacing the T-Con board. However, I found one YouTube video that made me go WTF? That can never work. The guy (another Dave) disconnects the panel driver ribbon cable, covers a bunch of contacts with sticky tape and that apparently fixes the picture. I chuckled at the idea and dismissed it. Further Googling didn't reveal anything more fruitful so I decided to try the sticky tape trick, expecting some cool effect as things broke in semi-deterministic ways. I used about 10mm of tape and it neatly cut out about 1/16 of the screen, stuffed the colour on about 1/8 of the screen, but low and behold, the dark scanlines were gone. I was like, WTF? Anyway, I progressively cut down the insulating bit of tape to about 3mm and everything seemed to be almost OK, except there was a hue shift in the first 1/16 or less of the screen. So, I cut of a bit more tape and stuck it on. Low and behold, it seems to be fixed and after a quick visual inspection I can not see any picture issues. I'll have to reassemble the TV and do a more through test.

Anyway, reason for the long post is to ask, how can this work? You'd think that blocking some of the data lines would cause some information to be lost and therefore degrade the picture. Does anyone have a explanation? Theories? I'm really curious about this one.

It would be educational to observe the data lines going to the panel with a scope and see how they work, but unfortunately I don't have a scope.

[Mechatrommer]

like this? Samsung LED Monitor Flicker/Interlaced Problem Repair
can you share the youtube link it maybe give another hope to my samsung monitor. anyway i think in future time i will not buying samsung monitor again.

[peteru]

like this? Samsung LED Monitor Flicker/Interlaced Problem Repair

No, that looks different. As I mentioned above, I had the defect on the entire screen and it was dark scanlines from the left edge, fading up.

can you share the youtube link it maybe give another hope to my samsung monitor. anyway i think in future time i will not buying samsung monitor again.

My original post has links, including the YouTube repair video - feel free to follow each one for specifics.

[Bud]

To me the most puzzling piece was wiggling of the taped cable in the connector
May have to do with rest of cable pins making a good contact after altering the mating surface thickness...

[xavier60]

It would be worth searching on the Badcaps forum. That's where these fixes tend to first appear with explanation.

[wraper]

Should be drivers on both sides of LCD panel driving same rows from both ends. Some driver IC/bonding failed on one side, so disconnecting one side fixes the problem. I've also seen fixes when all FPC cables on one side get torn off from LCD and it then works fine.

[peteru]

Should be drivers on both sides of LCD panel driving same rows from both ends. Some driver IC/bonding failed on one side, so disconnecting one side fixes the problem. I've also seen fixes when all FPC cables on one side get torn off from LCD and it then works fine.

Ah! That makes sense. If the driver on the left hand side was stuck on active, that would explain the black on the left side and the scanlines progressively becoming better towards the right hand side where the driver still works correctly.

So, presumably this fix is probably temporary, since the right hand driver now has to do double the work so it's more likely to fail down the track. I suppose some side effects of this "fix" will be slower response response time and less uniformity. As long as it's only every 8th or 10th scanline, it's unlikely to be noticeable.

Let's hope that this is good enough for a while, so that I can delay a purchase of a new TV until the (Australian) prices of 75" or bigger HDR TVs come down to a level where normal people can afford one.

[Dacke]

It looks pretty clever,  but I don't think the tape is actually blocking any contact points.  If you look closely,  the tape does not cover the contact points of the cable.  On the bottom of the cable you can see where the contact point is,  there is an indentation/crease along the cable (the contact point is not usually at the very end of the cable but slightly before it).  "Just the tip of the tape",  as he stated,  is folded over the end.  The tape has just enough thickness to cause the locking mechanism to provide more pressure on the contacts.  This is what I'm seeing anyway.

[wraper]

It looks pretty clever,  but I don't think the tape is actually blocking any contact points.  If you look closely,  the tape does not cover the contact points of the cable.

If you actually look at it, contacts are fully covered with tape.

[Dacke]

If you actually look at it, contacts are fully covered with tape.

Well my vision isn't the greatest, so you could be right there

[Shock]

This is another of those "unrepairable" panel faults, you might be interested in. Essentially what happens is he discovers 30V and -7 get to the driver pcb mounted horizontally (named vgh/vgl or v_on/v_off). He then checks if those same voltages are appearing on the vertical pcb and goes on to explain there are tracks in the glass panel corners that are easily broken. He then manipulates a test point with a resistor that affects the horizontal. After deducing the -7V was 0.2V he decided to jumper across two new wires between the PCBs to be sure it didn't reoccur.

Thanks to Raj who translated this for me.

[Rasz]

like this? Samsung LED Monitor Flicker/Interlaced Problem Repair
can you share the youtube link it maybe give another hope to my samsung monitor. anyway i think in future time i will not buying samsung monitor again.

like this: https://www.eevblog.com/forum/repair/help-me-save-a-samsung-from-landfill/msg2005232/#msg2005232
also a success story