|
I too have had similar experiences. 2 out of the 3 rear projections sets I've worked on so far have had bad convergance ICs. In a Philips 46" the shorted covergence ICs caused the power supply to shutdown. In a 42" Panasonic the fault was similar to yours: Reasonable convergance in the center of the screen, but it was further and further out the closer you got to the edges. In both cases replacing the STK convergence ICs and associated fusible resistors fixed the fault.
A couple of points:
Do not adjust any trimpots before checking/replacing the convergence ICs. In the Panasonic someone got in there before me and twiddled every one of the 30 or so convergence trimpots in an attempt get a better picture. This made the job much longer than necessary. A newer set will have less or possibly no trimpots.
Clean all the old heatsink compound of the heatsink and apply a thin even coat of new heatsink compound before installing the new ICs. In the Philips one of the ICs failed because someone applied the heatsink compound unevenly. Thick blobs in the corners and a air bubble in the center, this caused the IC to overheat and fail.
There's a 43" Samsung at my usual junk auction tomorrow. It's the first rear projection set I've seen that I'd actually consider getting. It too has a convergence problem, but it looks like there is potential for a very good picture (better than any of the sets that I've worked on and various other Pioneer, Sony, Panasonic and Mitsubishi sets I've seen). Most importantly for me it's 4:3. I know I'm wierd, but 16:9 just doesn't look right to me. I can watch letterboxed 16:9 content on a 4:3 set just fine, but I cannot stomach 4:3 content on a 16:9 set no matter how it's stretched/zoomed/letterboxed.
|