Pioneer rear projection tv: convergence or deflection?
 

I recently picked up, on the cheap, a Pro-98 Pioneer rear projection TV whose picture is collapsed over roughly the top half of the screen, down to the middle. In case that description doesn't make sense, a picture is here (just snow, nothing hooked to tuner):

http://209.234.77.62/tmp/pro98_raster.jpg

There are no visibly obvious problems on the deflection or convergence boards; I did touch up some suspect-looking solder points on both boards to no effect. I don't have a schematic (yet anyway) but the voltages at the test points I can find are about right. The guy I bought it from said it had failed in "exactly the same way" once before, and a Pioneer dealer had replaced a board, he didn't know which one. I did notice that on the convergence board, the large IC (STK4277) looked like it had been soldered in by hand, so I assume that's what the dealer really did. But when people say things have failed "exactly the same way" before, that isn't always true - sometimes they don't really remember what it looked like, they just remember it was wrong. So it's hard to trust that.

Based on some other reading suggesting that STK4277 chip commonly fails, I've ordered one - they can be had for under $20 - but the more I look at the symptom, the harder it is for me to believe that convergence has anything to do with making half the picture go that far out of whack, and there must be something wrong on the deflection board.

When the chip arrives later this week, I'll know whether the first impulse was right, but does anyone recognize the symptom?

Check all the large resistors for opens, and look on the same board for
STK4274. It is the vertical IC and can cause your collapse. It looks
like you probably do need the convergence chip, too. Good Luck!

Doug

That makes sense Doug! Thanks for taking the time to reply.