Vertical jumping on a UMK3 and a Polo

[rockin_rick]

I've got a dedicated Ultimate Mortal Kombat 3 machine with the original Polo monitor.  I have not yet done a cap kit on it, and am doing that soon regardless of the answer to this question.  I'm wanting to know if I need to order extra parts to go along with the cap kit to repair this...

When the pic is on the screen, it will randomly jump vertically a pixel or two.  It's just enough to annoy.  It seems like it is more active when there is motion on the screen.  Run time (AKA heat levels) don't seem to effect it.  Moving the horz position does seem to effect it.  It seems worst when the pic is centered via H-position.  If you move the screen off to one side (and thus partially off the screen) it almost goes away.

I've attached another board to this (a cherry master CGA board) and it seems rock solid.  Mame via arcade VGA also seems solid (albeit dim).  Does this mean that the UMK3 board is at fault (it self tests good), or (what I suspect) this is a function of the unusual 53Hz being sent to the monitor.  Obviously the Polo can handle this (or they wouldn't have used it in the first place), so I'm guessing some component(s) is weak/failed that makes the 53Hz 'just starting to get out of range'.

Any guesses?  Perhaps something starting to go out in the vertical deflection circuit?

Thanks,
Rick

[grantspain]

i would tell you how to fix this but you called me a dork the other day

[rockin_rick]

I wasn't calling you a dork - I was just trying to help out that other guy.  I, in no way, was trying to insult you, nor trying to discredit you or damage your reputation of stellar knowledge of arcades, and particularly monitors.    I purposely even tried to play it off that I only knew because his name was the same as mine, in an effort not to discredit you and to show that my intent was good.

I just checked that thread again and just now noticed your response - I missed it until now.  Rereading it, I now can see where you could have taken offense to this, I apologize, it was not my intension intention.

Thanks,
Rick

edit: spelling

[grantspain]

o.k the polo chassis suffer real bad from cap failure whether it be total or leaky,i guess from your post that you are getting some jumps rather than loosing sync,am i correct?
the caps most likely to cause any picture problems are c121,123,125,129,139,144,142,182,184
are you using composite sync or hor & vert sync inputs?

[rockin_rick]

The jumping was with composite sync on the UMK3.  With the cherry master (no jumping) it was also composite, while the AVGA (no jumping) was both H and V seperate.

If this doesn't seem to you that it's likely anything more than caps, then I'll replace those and see what happens.

Thanks,
Rick

[grantspain]

another thing you can try is connecting a 5k resistor from the sync on the input plug to the monitor frame earth,i am not 100% sure but i think mortal kombat send out a slightly weaker video signal as i actually had to check one the other day on a ceronix monitor and it had a little trouble locking and the picture was dull