My latest project is a Samsung LN-T3753H. This TV has distorted colors. The best way I can think to describe it is it looks like the picture is being displayed using a couple dozen colors instead of the usual millions. (Think of a JPG dithered down to a GIF or 16-color BMP, something like that). However, the onscreen menus are displayed without issue.
Searching on the Internet this is a fairly common problem with Samsung TVs, but no one seems to have found the problem. Most people give up and replace entire boards. The general consensus is the problem is most likely on the main video board and not the tcon board or the panel itself, since the menu is displayed correctly. So I'm starting my search on the main video board. All the checks I've run thus far (below) have turns up nothing.
1. Even though I don't suspect a main power supply, I checked the caps on the main power board. They are a crappy brand, but the ESR is fine and the output voltages are stable and in spec.
2. I removed and reseated the LVDS cable on both ends.
3. I checked the voltages of the few voltage regulators I've found on the main video board, they appear to be outputting correct voltages that are stable.
4. I checked the ESR of the surface mount electrolytic capacitors on the main video board. A few of the caps are out of tolerance. That said, I have not replaced them yet because surface mount can be a pain sometimes and I'm not convinced the problem is the caps. Using my oscilloscope I probed the positive lead of all the caps, the output voltage is very stable, no ripple. I'm not 100% sure this is a valid test, but it seems to me that if the ESR was a problem the output would have a lot of ripple.
5. I went into the service menu and found the option for the "panel type." I cycled through all available panel types without success.
Those are the tests I've run. There are several tests I haven't run yet, but I wanted to see if anyone has a suggestion first.
1. I have not removed the cover over the tcon board to inspect it.
2. The large metal heatsink/shield on the main video board, I have not removed it and there are surface mount electrolytic capacitors and maybe even voltage regulators underneath.
3. As I mentioned some of the caps are high on ESR, so I could replace them and hope for the best.
Does anyone have a suggestion here? I figured I would check for ideas before I start potentially destructive work (desoldering). The last time I tried to desolder a surface mount capacitor I pealed the pad and trace up. This time I think I'll use hot air instead of a soldering iron.
Searching on the Internet this is a fairly common problem with Samsung TVs, but no one seems to have found the problem. Most people give up and replace entire boards. The general consensus is the problem is most likely on the main video board and not the tcon board or the panel itself, since the menu is displayed correctly. So I'm starting my search on the main video board. All the checks I've run thus far (below) have turns up nothing.
1. Even though I don't suspect a main power supply, I checked the caps on the main power board. They are a crappy brand, but the ESR is fine and the output voltages are stable and in spec.
2. I removed and reseated the LVDS cable on both ends.
3. I checked the voltages of the few voltage regulators I've found on the main video board, they appear to be outputting correct voltages that are stable.
4. I checked the ESR of the surface mount electrolytic capacitors on the main video board. A few of the caps are out of tolerance. That said, I have not replaced them yet because surface mount can be a pain sometimes and I'm not convinced the problem is the caps. Using my oscilloscope I probed the positive lead of all the caps, the output voltage is very stable, no ripple. I'm not 100% sure this is a valid test, but it seems to me that if the ESR was a problem the output would have a lot of ripple.
5. I went into the service menu and found the option for the "panel type." I cycled through all available panel types without success.
Those are the tests I've run. There are several tests I haven't run yet, but I wanted to see if anyone has a suggestion first.
1. I have not removed the cover over the tcon board to inspect it.
2. The large metal heatsink/shield on the main video board, I have not removed it and there are surface mount electrolytic capacitors and maybe even voltage regulators underneath.
3. As I mentioned some of the caps are high on ESR, so I could replace them and hope for the best.
Does anyone have a suggestion here? I figured I would check for ideas before I start potentially destructive work (desoldering). The last time I tried to desolder a surface mount capacitor I pealed the pad and trace up. This time I think I'll use hot air instead of a soldering iron.
Attached Files
. It is a hotel TV, with a slightly different version of the Tizen operating system than the TVs at home.
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