K7000 (P447) glitch

[CharredPC]

 I recently got a nice Konami TMNT 4-player for $150, sold as "non-working." My intent was to use it for a MAME conversion, but within an hour of having it home, I had it up and going happily! The kids have been playing it for the past few days. The screen (WG 438761 with a P447 board) has great color, very little burn-in, and after a bit of a tune-up is very crisp and pretty (and huge!) The only issue (which would stop me from doing a MAME conversion as well) is that the left side of the screen is darker- or the right side is lighter, depending on how you look at it; I think the latter... I'll explain further on. The light/dark sides are seperated by a wavy deal that won't show up on camera right :p

So far I've diagnosed this much: I unplugged the jamma board and turned the unit on so I could verify it was the display and not the game creating the issue. Not only did I prove (like I thought) that the glitch is in the display, but it let me see the scan (raster?) lines clearly. I saw this:

http://www.dwarchive.net/issue.jpg

You can see that while the "darker" left side has nice parrallel lines, the right side's lines are slanted. These slanted lines are a bit flickery, which results in the "wave" in the middle of the screen, where they intersect. The tuning pots are useless for fixing this sort of thing, obviously, and the fact that it's only on one side has me a little stumped. Researching on the net tells me to get a cap kit. Ok, I'll do that in a week or two when I have the cash (a little tapped out after this $150 purchase! Yes, I know cap kits are under $9), but in the meantime I thought I'd pose the question here. Anyone see this before? Is there a certain single cap that often does this, and could be swapped out? So far, after digging through my parts box, I replaced C45 and C46 (both 16v 470uF); no change at all. I grounded the DC ground to the Frame ground to the chassy on the slim chance it was a freak interferance issue; no change. If it is a cap, it figures that it -would- be a big odd 160v one I don't have a replacement for...


TIA!

CharredPC

[Ken Layton]

Yup, needs a capkit. Remember that the k7000 was in production from 1986 thru 1992. Capacitors go bad with age and oftentimes more than one goes bad. That's why it's better to pull the chassis out once and capkit it than just change one bad cap today and next week have another one crap out.