D9200 bottom half of screen jitters vertically

[lilshawn]

of course now that there has been an influx of D9200 questions, now i'm having one of my own.

Came into the shop with the bottom of the screen jittering and separating vertically...seems to me like a vertical timing issue.

I went ahead and replaced  the vertical deflection IC301 cause, you know...usually vertical deflection issues is this and I buy these TDA8172's by the bag 25 at a time....and it was good for 3 or 4 days running 24/7...powered off the monitor... installed it back in the cabinet and pushed it aside. a week later plug it in, looks great, by 10 minutes in, things start warming up... it starts doing it again. same thing. bottom half starts twitching a little bit and before long (a couple hours) it's blarping all over. turn it off for 10 minutes...and it's fine again for a few hours.

so today I peel out and replace the IC407 since that also controls all the geometry and whatnot (I had one in a dead chassis that had a fried neckboard and toasted flyback. pretty sure it's good.) check the power resistors R314/R312 feeding IC301 all good.

Power it up, looks good for about 2 hours, leave and come back about 3 hours later and it's starting to get jittery again. so it's not that.

one thing i noticed. it's EXACTLY the bottom half of the screen doing it. you can draw a line horizontally through the exact center of the screen with it. the top half is 100% fine with zero issues. perfect in every way. as soon as the raster hits the middle, it's going all over. you could literally cover the bottom half of the screen and not know there was any issue. I wished I had a photo of it, but by this point i am so frustrated with it i left it till next week.

unplugged it for 5-10 minutes, power it up again... it's fine again... so it seems like it's heat related so i think I should probably pick up a can of freeze spray and blast some crap to see what gets cold and it smartens up.

to be continued...unless someone has seen this and has an idea? maybe? TIA! <3

[jennifer]

If I had to guess...my first thought would be a thermal issue on the yoke winding.

[lilshawn]

as with all these crap 9200's, it's yoke was at one time falling apart. it has been siliconed back together, so it is possible it's failing internally.

if it comes down to that, I think I MIIIIIGHT just have a 9200 tube up in graveyard storage... haven't looked in a while though.

thanks for the idea.