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Discussion Starter · #1 ·
I've managed to get this down to potentially a DMD board problem but I want to make sure there isn't anything I've missed.

Initial symptoms started with needing to replace a lamp frequently. The last lamp replacement I did didn't resolve the problem. The TV would turn on, if cold, and stay on for about 30 minutes. After being on for 20 - 30 minutes, the color would start flickering green and would cut off after a minute or so of doing this. It would then try to turn back on, and after a 3rd attempt, would stop and blink all three lights on the front panel. A new bulb did not resolve this problem and the lamp does not try to turn on at all anymore.

I checked to make sure the lamp cover was secured.

Tested the lamp cover switch and it was working.

Bypassed the lamp cover switch to test with the back covers off.

Checked to make sure the color wheel was turning. It was.

Checked for 280 VDC coming into the ballast. Tested at 310 VDC.

At this point, the service manual I was working with said to test Pin 10 on CN101 of the DMD board for 5 VDC. There was no voltage on the pin.

The service manual says to replace the DMD board. As best as I can tell, the Pin 10 test is looking for the Lamp Enable signal to be present. When I removed the DMD board to be ready for replacement. I noticed a discoloration around the DMD chip. The chip is a separate purchase from the board and I want to make sure I'm not spending money on something more than I need to. I feel like the chip or the color wheel could still be a problem. I know the LE signal is dependent on the color wheel, I don't know about any dependency on the DMD chip.

Any advice would be helpful.
 

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Plain ole user
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The discoloration is not necessarily a problem. I think the DMD board is a good guess but it could still be a bad digital board or power supply. I don't know of a good way to troubleshoot these further than you have, but it has been about 4 years since I was repairing sets like this.

I would check the supplies from the power supply to see if there are any obvious issues, and look for swollen caps.
 

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It looks like the board has been reworked to me. Cap failures on Samsungs are prety common so I would not be surprised. Look for any swollen caps or if you have an ESR meter test them.
 

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Discussion Starter · #6 ·
Didn't notice any swollen caps. I'll look them back over again. The color wheel is making a high pitched whine. Not sure if that's part of the normal operation. I didn't get this unit until it was already having problems.
 
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