Question about Mitsubishi VS-55601 55" Rear Projection Television
Question (see below for more details): The big question I have is this: If the convergence chip went bad, why would the TV exhibit the convergence problem, then have it go away for a day, then come back again? I would think once it goes bad it would stay bad? The problem was immediate upon turn on, then I turned it off for 10 minutes, back on and everything was back to normal (and for several hours that night). Then the following day and ever since, the problem is back. Thinks I tried: I removed the convergence board (disconnecting all connections) and found the following: 1. No resistors were burned, no overheat marks, and all the pins on the SK convergence chips looked ok. 2. I saw that one resistor and 2 pins on the VGR connector had flux near them (assuming this means someone had replaced these in the past). By tracing the solder traces these seem to be related to the center convergence chip and trace to the VGR connetor (assuming this is for the green convergence). 3. I removed (solder) and resoldered all the main resistors and flowed clean solder on them. I also reflowed the solder to all pins on the center convergence chip. 4. I tested all large resistors and read consistant values for each (1.7 ohm, 4.5 ohm, and 0.555 kOhm) 5. On powerup, I jiggled all connectors to the convergence card and the corresponding connectors on the yoke of the green tube (carefully!). I also adjusted the screen and focus for the green tube (worked fine). None of the above changed the result. I still have convergence issues with the green tube and *only* in the vertical direction. I spoke with a local tech friend who said something about each chip has vertical and horizontal convergence sections and there are separate sections per color (he said 2 chips: 1 vert 1 horizontal, then 3 colors per chip, but doesn't work on Mitsubishi's). From what I can tell this is 3 chips (1 per color) and guessing each chip has vert and horizontal sections. Is the above correct? If so it would seem the chip could be bad for the vertical section. The big question I have is this: If the chip went bad, why would the TV exhibit the problem, then have it go away for a day, then come back again? I would think once it goes bad it would stay bad? I may order the chip and just replace it and see if anything changes, given I am dreading any manual convergence after replacement. Is there a good source for these chips? The chip is an STK-391-020. Thanks for all the help! :) Buzz
Yes, they go bad interment because they have a large current go thru them and they generate heat, they are mounted on a heat sink with white silicone to help disapate heat. replace both not just one, try MCM Electronics get heat sink compound also
Posted on Oct 17, 2006
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