Samsung LN46A550 Picture Issue

[T-Rex]

Hi, I've got an issue with my LN46A550 that just started and I'm not sure if it's in the PS, TCON or Mainboard and was hoping somebody could dx this from pictures to at least have a high degree of confidence in what part to replace. I looked at the PS and did not see any obviously bad caps and I removed and reseated all 3 connectors on the tcon board with no changes. I also went into service mode and did a factory reset.

Any idea what the problem may be based on the pictures? Thanks!

Steve

[johnboy1313]

Re: Samsung LN46A550 Picture Issue

Because of the sharpness of the image, meaning it's not washed out, I'm gonna say main board. You can test the T-Con but I'm not able to tell you how. Highly unlikely to be PSU

[Glitcher]

Re: Samsung LN46A550 Picture Issue

Wrong panel setting? At first I thought gamma chip but I looked up the tcon for this model and it doesn't seem to have the chip. So I would guess main board as well, try to access the factory settings and change the panel setting.

[T-Rex]

Re: Samsung LN46A550 Picture Issue

Thanks for the comments so far. What do you mean by 'panel setting'? You talking the panel option or model setting in the Option Byte menu as in https://www.badcaps.net/forum/attach...&d=1354241249? How would that change on it's own? I'll go look at that.

For reference the T-Con board is 35-D025860 and the main board is BN94-01723W.

[Glitcher]

Re: Samsung LN46A550 Picture Issue

Hmm, I'm wondering looking on the tcon model number, does your tcon have the AS15 chip? Can you post close up photos of the tcon?

[tibimakai]

Re: Samsung LN46A550 Picture Issue

It looks like a gamma chip went south.
At shopjimmy, shows a A19-H16 chip.
I have never replaced one of these yet, only the A15-F or G.
You would be able to measure the test points on the T-con.
They have to increase gradually from one test point to another.
The test points are on the top center where it is labeled Gamma. Strat from 1, 2, 3...
It there is one that is out od the line, then most likely the Gamma chip is bad.

[T-Rex]

Re: Samsung LN46A550 Picture Issue

Yes, it looks like a A19-H1G chip (attached). So you are talking the 2 square pads of contacts by the ribbon cables labelled 1-9 and 10-18 on the opposite side? And these should be measured to ground. And you say the voltage on each sequential number should be higher, like pin 1 = 1 volt, 2 = 2 volts, 3 = 3 volts (examples)? Sorry, I'm not an electronics tech but I can sorta figure it out with guidance - thanks!

[mmartell]

Re: Samsung LN46A550 Picture Issue

Yes you got it. A plotted graph of the points should either be linear or slowly curving (tom ?) Any big deviations are likely chip malfunction.

[tom66]

Re: Samsung LN46A550 Picture Issue

In box marked GAMMA. Voltages will either INCREASE or DECREASE but not both. 1V, 1.5V, 2V, 3V, 4V, etc. and 4V, 3V, 2V, 1.5V, 1V are both OK. 4V, 2V, 3V, 1V, 1.5V is NOT OK. The voltages will not correspond with the numbers but will range from around 0V to 15V.

[T-Rex]

Re: Samsung LN46A550 Picture Issue

This is what I got...

1. 15v
2. 12.9
3. 12.08
4. 11.2
5. 10.8
6. 10.43
7. 9.99
8. 9.35
9. 8.78

10. 6.42
11. 6.62
12. 6.66
13. 9.38
14. 9.41
15. 9.40
16. 4.15
17. 2.79
18. 0.48

So does that mean the gamma chip and hence the tcon board is bad since 16-18 went down instead of up?

Do the pictures match symptoms of bad gamma/tcon? Is the consensus to replace the tcon board (I don't have the skill to just change chip)?

Is there a way to rule out bad main board like originally thought?

Thanks!

[johnboy1313]

Re: Samsung LN46A550 Picture Issue

In my experience, a faulty gamma chip will cause similar problems, but the entire picture will be slightly washed out. It's kinda hard to describe. Both times I've had the kind of image you show, a new main board fixed it.

Gamma Problem
https://www.badcaps.net/forum/attach...5&d=1387969634

Main Board Problem (not the best image)
https://www.badcaps.net/forum/attach...1&d=1365633902

Do you see how the colors are vivid in the second pic? Kinda like your pics.

Try diconnecting any sources from the set, power it on, and pull up the menu. If the menu looks fine with a source disconnected, it's not the gamma IC.

[budm]

Re: Samsung LN46A550 Picture Issue

You have bad Gamma voltages. Similar picture to one of my repair.
http://s807.photobucket.com/user/bud...tml?sort=3&o=2

[T-Rex]

Re: Samsung LN46A550 Picture Issue

Hmmm, I can see partly both. I see the problems in johnboys mainboard picture but I also definitely see the issues in budms picture.

The menus also do look off with no source - they are clear but color is kinda off in places like white are yellowed and the gradients are rough instead of smooth.

With the voltages off I guess it's safe to say AT LEAST the tcon needs to be replaced. I'd just hate to invest in tcon then still have to replace mainboard. I think at that point it may just warrant a new tv . I guess there is no way to test the mainboard to tell if it is also bad?

I assume shopjimmys is about the best place to get a tcon?

Thanks again...

[tom66]

Re: Samsung LN46A550 Picture Issue

Yep, agreed. Gamma curve is wrong. You will have to replace t-con or gamma chip. I doubt there is another fault.

The symptoms vary. Oversaturated colour and blown out whites are common. But sometimes, it can be as simple as the picture looking a little "off" -- colours not quite right, for example.

[T-Rex]

Re: Samsung LN46A550 Picture Issue

Thanks guys. I ordered a tcon board 2 day from shopjimmys. I will report back Fri or Sat with results.

[tibimakai]

Re: Samsung LN46A550 Picture Issue

Sorry, for late answer, but I agree with Tom, bad Gamma chip.
I have just replaced one on a 46A630, but it was A15, not A19.

[tom66]

Re: Samsung LN46A550 Picture Issue

BTW: forgot to add, the comparison for incorrect voltages is done across the whole curve, 1-20 or whatever, not over each block.

[T-Rex]

Re: Samsung LN46A550 Picture Issue

Ok, so it was 13-15 that made this defective. If those descended from 6 - 4 volts then it would have been ok, but the jump up to 9 is what indicated its bad I guess. Funny how just a few volts can screw it up so bad.

[T-Rex]

Re: Samsung LN46A550 Picture Issue

So I just wanted to update this and close it out. I installed the new tcon board and it fixed the problem completely, the picture is fine again. I just wanted to sincerely thank all of you who helped me troubleshoot this. The measurement of tcon voltages was a key item leading to a good Dx and fix. I am active on a large Home Automation forum where there is a similar level of help we all give and it's great to see that here as well where everyone chips in and helps the newbies and stuff, so thanks again for the assist.

[tom66]

Re: Samsung LN46A550 Picture Issue

Nice to hear, enjoy the TV! It's a shame Samsung put a Chi Mei panel in this model, you'd expect better TBH.