Nasty Caps

Reznor007's post here got me thinking a bit about one of my old problematic jamma boards.

My Block Out board has issues with distorted sound and badly bleeding colors (regardless of the RGB pot settings on the JROK) so I had a look at it. The three largest electrolytic caps are pretty nasty looking and look like they could be leaking. Also, testing with a multimeter shows that their current values don't match their markings (not even close).

I guess this is probably a stupid question but should I expect replacing all the electrolytics to yield any sort of improvement?

Do you have other boards that work OK with your set up ?

Game boards have electros in the audio output stage and also sometimes to filter noise on the 5 and 12 volt rails. See them bottom right on this Block Out board (they are all to do with audio output)



Its possible a dodgy cap could cause audio distortion, but bleedind colours seems more of a monitor/TV issue.

Add a lot of filth and some rust to the picture and it'd look exactly like my board.

My MVS, Final Fight, and Bloxeed all work fine on my setup (JROK + 32" Sony Wega CRT).

I pointed some arrows (the black ones) to a lot of smaller caps (mostly 10uF). Most of those measure wrong as well. What kind of effect would you expect that to have? Are these even electros (if you can tell)?

Also, one of the two oscillators (I'm working from memory right now and I don't remember which one) marked by red arrows has a dent in it (shipping damage). I had a hard time even getting this board to display as well as it does when I first got it and James thought the board might be generating a slightly off sync signal. Could a damaged oscillator cause bleeding or would it be more likely to prevent the thing from working entirely?



Also, if it helps to know: When I was troubleshooting the sync problem, I connected the board to an old composite-only C64 monitor, on which it displayed almost perfectly (it was a little noisy, but completely acceptable otherwise). However, on an upscan converter (S-video to VGA), the colors still bleed (even worse than the TV).

Well, bleeding MIGHT be a damaged oscillator, as some things might be offset or something... but I don't think so. Just be glad your board is still outputting a bad signal and hasn't moved on to the "ZOMG IT BRAKES MY MONITORS!!!" stage. My old Double Dragon 3 board will fry any monitor it's connected to in about 5 hours because of some incorrect signal or voltage or something. Haven't really looked as it's pretty worthless to me.

SpamYouToDeath said:

My old Double Dragon 3 board will fry any monitor it's connected to in about 5 hours because of some incorrect signal or voltage or something. Haven't really looked as it's pretty worthless to me.

Click to expand...

Sell it on ebay as "untested"