• My 98¢ 40" TV
    1 replies, posted
To the mods: I wasn't sure if this should go in HW/SW or DIY, feel free to move it if you see fit. I was given a TV with some unspecified problem a while ago, and had been meaning to work on it for over 6 months. It turns out it would work for about 45 minutes, then the picture would turn into a constant slur of colors and the set would emit a loud noise straight from hell (as my sleeping roommate found out), which wouldn't stop until you literally cut power to it. Well, I finally got around to fixing it, and here's how. I popped it open and visually inspected the capacitors, they all at least [I]looked[/I] fine. Then, my friends and I realized, the problem could be anywhere on the board, but it was almost definitely because of heat, (because of the ~:45 delay, which would get shorter if you reset the TV after crashing). So what do you do to find/detect a heat problem? You get out the hairdryer and the canned air. We heated each of the suspect boards (with the hairdryer on the lowest setting) until we were content with their hotness, and then we watched what would happen. We found out that the failure could be replicated by heating a specific chip on the logic board. We also found that it could sometimes be reversed by cooling the chip. Here's a tip: Holding a can of Dust-Off (or any other "canned-air" product) upside-down will expel the refrigerant in the can. The refrigerant, by nature, will drop greatly in temperature when depressurizing, and will be beyond freezing cold. You can use this to chill a circuit. If you're worried about subjecting the components to shock, the compressed air alone might cool it enough, or you can tilt the can to get a mix. We figured out that a couple of PC fans we had lying around would keep the chip cool as a cucumber, and it ran for a solid 2 hours without any failure. We then cut holes in the case and installed the fans, which we soldered to a DC power jack, and then plugged into a 12V DC power supply I had lying around. It's been running beautifully all day with no problems! The best part is, the only parts I had to buy were a couple of nuts and bolts to hold the fans in place, for a grand total of 98¢. I also learned some valuable lessons, such as "What 120VAC feels like", or "Domino's is open until 3AM". I'll post photos of the finished TV later today.
Good job! I think it's a much better feeling to know that's you've fixed it yourself, instead of dropped it off elsewhere to get it fixed. Also, come back after you've felt 230VAC. Now that's a bitch.
Sorry, you need to Log In to post a reply to this thread.