Samsung LCD heat problem...?
Hi all electronics Gurus! 
Here's a first-time post from France, (just across the border to Geneva, Switzerland.)
I have a strange problem with a Samsung LCD that I bought second hand. (Yes, out of warranty.)
--- ID ---
Samsung 40" LCD television
Model no: LE40A536T1FXXC
Serial no: AT4F3SLQA12103N
Version: CN01
Mainboard: BN94-02459A (Well, um, if I found the right sticker?)
--- Some symptoms ---
When switching it on cold there's no problems at all with it, all works perfectly fine and the picture is excellent. (Well, at least as good as it gets on an old LCD like this one - but to me it looks great.) So far so good.
(One problem it does _not_ have is the on-off-on-off-on-off-on-off phenomenon that I have read happens quite often with Samsungs... (Knocking on wood.))
Ok, moving along with the error description now.
-After about 10 minutes-
The darker parts of the image start to get "strange", and strange in this context means; the color fades a bit to slightly green-ish and the other colors start to get gently washed out.
-After about 20 minutes-
More of the above.
-After about 30 minutes-
Even more of the above, but not so much if the "green" anymore in the dark parts, just worse colors.
-After about 1 hour-
By now it starts to get really annoying to watch the image. The dark parts of the image are really distorted and the other parts of the image are seriously washed out.
...And here's a strange part that perhaps might be a good lead to what the problem might be; (?)
All the black parts are (more or less) fine and the on-screen menus are good. It does not matter if I use the HDMI1 or an RCA input, all the image sources are showing the same symptoms.
--- What I have tried ---
Opened up the poor thing and had a look if there would be anything "obvious" problem that would catch my eye. Nothing. All caps _look_ ok, meaning none exploded
, no bulging at all, no leaks, all FET:s and diodes look good, etc...
Well, being the curious person that I am, I thought that I would try an old little trick. I let the beast heat up to "maximum bad picture" and then I opened up a can of "Kälte 75" cooling spray. I started quite gently spraying caps, cooling fins, IC:s, individual components and then the PCB:s in general. All with due pause between components and constantly checking if there would be any change in the image.
...But there was no change.
If I switch the beast off for a while to let it cool the picture is -again- perfect for a while but as it heats up it starts getting worse again. (Well, I guess it's heat-related...?)
--- What I have not tried ---
Replacing the caps.
If you think that this might do the trick I'll of course do this.
Dropping it off a cliff and calling my insurance company.
--- And since a picture says more than a thousand words ---
...Here are four pictures where I tried to catch the problem, not really easy to get it photographed. And what's even more bizarre is that the TV picture looks better in my camera than what it does on the TV?
Pics are; Ice age and Clarkson via RCA (from an old Xbox) and a 2x a local (French channel) in HD.
--- Some info about myself? ---
I have been repairing just about anything that breaks From GSM phones to computers, laptops, TV:s, washing machines, various kitchen appliances, many Xerox machines, cars (really everything - including complete engine rebuilds), motorcycles, my hydraulic backhoe, tractors and ~20tonne tracked excavator and skylift too. 
Ok, slightly offtopic in the end of the list. ...Having said all this I'm still a complete n00b (beginner) when it comes to LCD:s...
I have a thermostatic Weller WECP-20 soldering iron (that I got as a kid), oscilloscope(s), power supplies, multimeter(s), etc. And at work there's even a particle accelerator if I need one. (Yes, I work at CERN.)
...So there goes. Any and all tips are very welcome! Thanks a lot in advance!
Yours respectfully,
Magnus
Here's a first-time post from France, (just across the border to Geneva, Switzerland.)
I have a strange problem with a Samsung LCD that I bought second hand. (Yes, out of warranty.)
--- ID ---
Samsung 40" LCD television
Model no: LE40A536T1FXXC
Serial no: AT4F3SLQA12103N
Version: CN01
Mainboard: BN94-02459A (Well, um, if I found the right sticker?)
--- Some symptoms ---
When switching it on cold there's no problems at all with it, all works perfectly fine and the picture is excellent. (Well, at least as good as it gets on an old LCD like this one - but to me it looks great.)
So far so good.(One problem it does _not_ have is the on-off-on-off-on-off-on-off phenomenon that I have read happens quite often with Samsungs... (Knocking on wood.))
Ok, moving along with the error description now.
-After about 10 minutes-
The darker parts of the image start to get "strange", and strange in this context means; the color fades a bit to slightly green-ish and the other colors start to get gently washed out.
-After about 20 minutes-
More of the above.
-After about 30 minutes-
Even more of the above, but not so much if the "green" anymore in the dark parts, just worse colors.
-After about 1 hour-
By now it starts to get really annoying to watch the image. The dark parts of the image are really distorted and the other parts of the image are seriously washed out.
...And here's a strange part that perhaps might be a good lead to what the problem might be; (?)
All the black parts are (more or less) fine and the on-screen menus are good. It does not matter if I use the HDMI1 or an RCA input, all the image sources are showing the same symptoms.
--- What I have tried ---
Opened up the poor thing and had a look if there would be anything "obvious" problem that would catch my eye. Nothing. All caps _look_ ok, meaning none exploded
, no bulging at all, no leaks, all FET:s and diodes look good, etc...Well, being the curious person that I am, I thought that I would try an old little trick. I let the beast heat up to "maximum bad picture" and then I opened up a can of "Kälte 75" cooling spray. I started quite gently spraying caps, cooling fins, IC:s, individual components and then the PCB:s in general. All with due pause between components and constantly checking if there would be any change in the image.
...But there was no change.
If I switch the beast off for a while to let it cool the picture is -again- perfect for a while but as it heats up it starts getting worse again. (Well, I guess it's heat-related...?)
--- What I have not tried ---
Replacing the caps.
If you think that this might do the trick I'll of course do this.Dropping it off a cliff and calling my insurance company.
--- And since a picture says more than a thousand words ---
...Here are four pictures where I tried to catch the problem, not really easy to get it photographed. And what's even more bizarre is that the TV picture looks better in my camera than what it does on the TV?
Pics are; Ice age and Clarkson via RCA (from an old Xbox) and a 2x a local (French channel) in HD.
--- Some info about myself? ---
I have been repairing just about anything that breaks
From GSM phones to computers, laptops, TV:s, washing machines, various kitchen appliances, many Xerox machines, cars (really everything - including complete engine rebuilds), motorcycles, my hydraulic backhoe, tractors and ~20tonne tracked excavator and skylift too. Ok, slightly offtopic in the end of the list. ...Having said all this I'm still a complete n00b (beginner) when it comes to LCD:s...I have a thermostatic Weller WECP-20 soldering iron (that I got as a kid), oscilloscope(s), power supplies, multimeter(s), etc. And at work there's even a particle accelerator if I need one. (Yes, I work at CERN.)
...So there goes. Any and all tips are very welcome! Thanks a lot in advance!
Yours respectfully,
Magnus
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