White line in Ms. Pac-Man

bear1

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My Ms. Pac-Man cocktail table has a white horizontal line across the screen only during the intermissions and the character introduction part of the attract mode. Is this a problem with one of the chips? Thanks.
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Confirmed fix for: Pac/Ms. Pac Line at top of screen.

Pac/Ms. Pac line at the top of screen fix.

Parts needed:
-------------
(4) 680pf disc capacitors. (voltage not important but the higher the voltage the bigger the physical size of the capacitors.
I used 1000v caps in the demonstration pictures as they were all I had at that moment. 500v or less will be easier to work with.
Some thin diameter pieces of heat shrink tubing.

Refer to the pictures to determine the correct area of the pcb where the capacitors will be added.

It is suggested you remove the solder from the pads on the pcb so that the capacitors can be inserted into the newly cleaned holes
left behind for a secure fix. Use solder wick or a desoldering tool for this.

If you are unable to remove the solder you can still install the capacitors, just must make sure that no leads touch each other when finished.
Simply solder the tip of a capacitor lead directly to the pad - snip excess lead before soldering. No harm will come to the pcb if the leads are
touching but the results will be discolored or distorted video when powered up.

Cut a small piece of the heat shrink tubing small enough to cover one leg of the 680pf capacitor but leave enough of the lead so that it can be
soldered to the pcb. See picture.

Install the leg of the capacitor with the heat shrink tubing into pad as indicated in the picture. Install the other capacitors into the other
pads the same way. You can use hot glue to use as an insulated barrier for the leads going to pads instead of the heat shrink.

Make sure that no lead of the individual capacitors going to a solder pad on the pcb are touching! All free leads of the capacitors not soldered
to a pad will be connected to ground. It is ok for any and all of these leads to touch and be soldered to a common ground point.

Any ground point can be used but the closest one used will be a cleaner looking fix. See picture.

After installing the capacitors and checking to be sure no leads going to the individual pads are touching... the pcb may be tested with power and
checked for correct operation. The video should be perfect and clear as it was. Depending on what screen during the game the line was on you may
notice that it is gone immediately or have to play a couple of screens to get to the first intermission. The line is gone and should never return.

Enjoy!
 

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Component drift due to age? Basically the video signal is being slightly over driven. The capacitors are just applying attenuation on the video signal lines. I wouldn't consider it a hack fix in any way because it's the same circuit Sega used on Pengo pcb's which are very similar in design to this board. Maybe Sega just had foresight.
 
Component drift due to age? Basically the video signal is being slightly over driven. The capacitors are just applying attenuation on the video signal lines. I wouldn't consider it a hack fix in any way because it's the same circuit Sega used on Pengo pcb's which are very similar in design to this board. Maybe Sega just had foresight.

Those aren't "video signals" and the caps aren't "attenuating" them.

It's just slowing down the edges on the COL bits between the 157 and the PROM to slow down the edges and lessen the glitching when the retimed ~HBLANK switches..

Pengo schematic doesn't have those caps, but there's an extra gate delay between the reclock ~HBLANK and the 157 where it's combined with ~VBLANK -- putting a small cap on 3B:15 will probably accomplish the same thing on Pacman.
 
Stretch the width and turn the brightness down.
 
Ha Ha. You're right, they are not on the schematic. They are on the pcb though. Maybe your terminology is more correct for what is being accomplished. I only copied what is in plain view, and it worked great.
 
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