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Old 12-11-2018, 06:06 AM   #1
Grunder
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Default Samsung PS42A410 Vertical green bars

Hi Guys,

Samsung PS42A410.

Fault:
12 green vertical bars evenly spaced across screen (photo)

Measurements Taken.

The pins on the sockets weren't numbered, so I used the pins with the black cables as pin 1, and then considered each socket to have pin 1 at the same place. (Photo)

CN801.

1. pson 0v 2. n.c 0v
3. std5v 5.2v 4. rtn 0v
5. rtn 0v 6. rtn 0v
7. 13v 12.7v 8. bv_amp 12.7
9. rtn 0v 10. rtn 0v
11. rtn 0v 12. rtn 0v
13. d5.3 5.2v 14. d5.3 5.2v
15. d5.3 5.2v 16. d5.3 5.2v
17. rtn 0v 18. rtn 0v
19. 13v 12.7v 20. rtn 0v
21. 13v 12.7v 22. d13v 12.7
23. n.c 0v 24. n.c 0v.

CN807

1. 5.3 5.2v
2. 5.3 5.2v
3.&4. rtn 0v
5.&6. n.c 0v
7. pson 0v
8. n.c 0v
9. vson 0v
10. std5v n.c 0v

CN810.

1.&2. vs 207v (was 205v/ adjusted up)
3. rtn 0v
4. va 54v (was 53v/ adjusted up)
5. rtn 0v
6. vg 14.7v

Notes

1. I saw the adjustment for the vscan but couldn't find measurement points.
2. The 5.3v fluctuates between 4.7v & 5.1v at about 1 cycle a second which seems to correspond to the green led flashing on the logic board.

Repair attempt.

After stripping the set down I noticed the 12 green bars lined up with the 12 ribbon cables that connect the buffer to the panel and reckoned that all 12 ribbon cables or their sockets couldn't all be identically faulty.
In my mind it had to be something common to all 12 sockets.
So I changed the caps that look responsible for "smoothing" the VA voltage to the buffer board. No luck. (photo)
I used my esr meter to check the cap on the power supply also responsible as a smoother/resivoir cap on the VA line. looked good.
I also need to point out the purple & yellow lines marked with arrows in the second photo.

I dont know where to go from here. Could somebody please help.
Attached Images
File Type: jpg Pict 1.jpg (255.6 KB, 12 views)
File Type: jpg Pict 2.jpg (697.2 KB, 15 views)
File Type: jpg Pict 3.jpg (550.4 KB, 12 views)
File Type: jpg Pict 4.jpg (411.7 KB, 7 views)
File Type: jpg Pict 5.jpg (409.5 KB, 4 views)
File Type: jpg Pict 6.jpg (594.8 KB, 4 views)
File Type: jpg Pict 7.jpg (611.0 KB, 3 views)
File Type: jpg Pict 8.jpg (622.5 KB, 3 views)

Last edited by Grunder; 12-11-2018 at 06:10 AM.. Reason: missing info
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Old 12-12-2018, 04:04 AM   #2
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Default Re: Samsung PS42A410 Vertical green bars

14 Views and no response... anything?
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Old 12-12-2018, 05:12 AM   #3
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Default Re: Samsung PS42A410 Vertical green bars

am I missing something here?

The voltage readings did have spaces when I entered them? they bunched up once posted??
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Old 12-12-2018, 05:43 AM   #4
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Default Re: Samsung PS42A410 Vertical green bars

You're obviously getting corrupted data to each bank of outputs to the panel, so either a connection problem between T/CON, shorted lines either on T/CON, cable or buffer board input or distribution lines to each bank across the board, or bad components on T/CON (bad processing chip or memory or whatnot, depending on design.)

Does re-seating the cables from the T/CON to X-Buffer board change the pattern at all? If it is not physical connection related it is probably T/CON but could obviously also be a problem on the X-buffer board itself with shorted lines rather than the typical buffer failure of individual section's output.
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Old 12-12-2018, 07:40 AM   #5
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Default Re: Samsung PS42A410 Vertical green bars

Hey Drussell, looks more like a logic control board as it s a plasma, and not an lcd.

Yip, should have mentioned that I done all the usual checking/seating all plugs & sockets.

I dont know if im searching using the wrong criteria, but dont see same or similar set or fault in badcaps?

thanks man, will persevere...
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Old 12-12-2018, 08:38 AM   #6
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Default Re: Samsung PS42A410 Vertical green bars

Quote:
Originally Posted by Grunder View Post
Hey Drussell, looks more like a logic control board as it s a plasma, and not an lcd.
Indeed. I should have looked closer, was just looking at your first couple screen photos. These kinds of faults are more common on LCDs but the principle in this part of the signal chain is the same. Something is going wrong between where the picture is generated to be sent to the buffer boards along the bottom and since the problem repeats on every set of buffers, it is most likely the signal getting to the buffers is mangled rather than it being the buffers itself (mangling only its outputs) like it would be if you had one whole vertical stripe from one bad buffer chip, etc.

It is still possible for it to be a fault in a single buffer chip but would have to be something funky on the input side corrupting some of the data lines, which of course are shared on the input side coming from the logic board in the middle which is doing the same kind of job as on an LCD "T/CON" board, regardless of what they call it.
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Old 12-12-2018, 08:43 AM   #7
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Default Re: Samsung PS42A410 Vertical green bars

Does anything change (other than losing half of the picture) if you disconnect one or the other of the X-Buffer boards from the logic board, or does the TV fault out if you try it with one side disconnected. Most will power up with only half the screen connected and if you happen to get good picture on one side but the other one messes up the whole screen then the fault is probably in that half of the X-Buffer set rather than in the center logic board.
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Old 12-12-2018, 08:54 AM   #8
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Default Re: Samsung PS42A410 Vertical green bars

Have you run test patterns yet?
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Old 12-12-2018, 11:25 AM   #9
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Default Re: Samsung PS42A410 Vertical green bars

Quote:
Originally Posted by drussell View Post
Does anything change (other than losing half of the picture) if you disconnect one or the other of the X-Buffer boards from the logic board, or does the TV fault out if you try it with one side disconnected. Most will power up with only half the screen connected and if you happen to get good picture on one side but the other one messes up the whole screen then the fault is probably in that half of the X-Buffer set rather than in the center logic board.
Thanks, I haven't tried this procedure on this plasma, but have used it to good on a couple of lcd's. Not knowing plasmas as well as i do lcd's i was scared i would damage something.

Now the bad news.....I think I stuffed up. On replacing the long metal frame/ heatsink that covers the buffer board, i think i damaged the foils that go from the buffer to the panel. Now i have missing picture on both sides.

I dont know if like lcd panel's, the foil is bonded on meaning i've wrecked the panel? I haven't included a photo of the screen. very depressing
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Old 12-12-2018, 11:33 AM   #10
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Default Re: Samsung PS42A410 Vertical green bars

Quote:
Originally Posted by tom66 View Post
Have you run test patterns yet?

Thanks Tom, I know, I should have. I've read it so many times while looking at other post's. I guess I should have. Must have had a brain fart or something.

Anyhows, as you can see from the above post, it looks like it might be toast.

Like Drussel was saying, i also think it's corrupt data getting to the buffer meaning it could be either the main or logic board?. The on board test patterns would have really helped. Thanks.

Knocking off now. Tomorrow brings a new day. Cheers

Last edited by Grunder; 12-12-2018 at 11:47 AM..
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Old 12-12-2018, 01:26 PM   #11
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Default Re: Samsung PS42A410 Vertical green bars

If you've damaged the ribbons along the bottom of the plasma panel, it is indeed toast. Sorry.

Have some fun if you get the picture back. Power it on without the heatsink and watch the buffer ICs cook. You'll get an interesting show of rainbow lines before it dies for good.
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Old 12-13-2018, 12:21 AM   #12
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Default Re: Samsung PS42A410 Vertical green bars

Thanks Tom & Drussel. After much mental deliberation i've decided to not spend any more time on this repair.

The fine purple and green line's bother me. (methinks the panel is faulty).
Even if it wasn't the panel, cost in time and spares required earmark it for retirement. Thanks for the input. Mike
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Old 12-13-2018, 02:37 AM   #13
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Default Re: Samsung PS42A410 Vertical green bars

The alternating purple/green lines are not a fault with the panel - that would be a control board or main board fault.

If you have specific, individual and random pixel lines then that is a fault with the panel.
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