Atari Millipede Monitor "Droop"

[milricky]

The entire left side of the monitor "droops" down about 1 inch on my Atari Millipede game (see attached pictures).  I'm looking for help on how to make this repair.  Thanks in advance to all for any information shared.  I believe the machine was built in 1982.

[KaPH33n]

Is it the original monitor chassis or a replacement? either way I would start by tweaking the horizontal hold potentiometer if it has that control. Likely on the chassis directly.


The monitor also looks a bit green, yes i know millipede is a green heavy game. I would try adjusting your green cutoff or bias control. Probably on the neck board.


Try these two fixes first and see if you're happy enough with the results.


If you want to "harden" or "shop out" the machine I would go through and do the following:
Since this game is quite old, you probably should start by replacing all of the electrolytic caps in the cab. Start with the big blue no matter what unless it's been replaced in the last decade. Probably should recap or rebuild the ar2 but do some checks and see if everything is ok first. The game board has a few caps on it as well. And of course, recap the monitor chassis.


If you do choose to replace the trackball with a new one be aware that the new ones from happ have a different pinout than the old original ones in these atari games. You may need to look up the pinout or do some wire swapping on the harnesses to make it work correctly.

[milricky]

Thanks so much for the direction.  I'll try to locate the "horizontal hold" and "green cut off control".  Do you know if they are labeled, or what I need to look for to find them?

Since I don't have any real experience working on these machines, do you know where I can learn about replacing the caps?

[KaPH33n]

take off the back door and try to identify the monitor chassis. it could be several different makes/models but they should all have a horizontal hold control and a hopefully bias/cutoffs. Make sure to be careful around the thick red wire that goes to the back of the monitor. That's the anode cap and it the insulation holds in thousands of volts (even when it's powered off). Research discharging monitors if you are going to recap the chassis.


Maybe try finding the manual for the chassis online... but you shouldn't really need it for those two settings.

[milricky]

So I'm striking out so far.  I did find and tried adjusting the H-Size, H-Position, V-Size and V-Hold, but this did not help the "droop" at all.  I was able to clean up the picture with the color & brightness adjustments.


Any other thoughts or suggestions?  The droop is less when the machine is first turned on and gets larger once the machine warms up.

[KaPH33n]

Is there no way to adjust the H Hold though? That is the symptom of the problem I'm seeing on your monitor. Remember "horizontal" on the monitor is the longer dimension. The monitor is rotated and mounted 90 degrees in a vertical game like millipede but the controls will still refer to the monitor in its native orientation. Because there is curl just at the edge of the screen in the horizontal direction I suspected the horizontal hold. It could also be a cap issue and doing a monitor chassis cap kit could help or fix the issue. If there is a horizontal hold pot it is a lot quicker to try to fix it that way.


I'm not sure what monitor that is... I think it is the matsushita 19 which would likely be an original monitor chassis.
https://www.arcade-museum.com/manuals-monitors/Atari%20Monitor%20TM-220%201st%20Printing%20Matsushita%2019in.pdf


if it is that monitor page 5 of the manual says to adjust R505, which is basically in the center of the pcb.

[milricky]

Success!  It wasn't easy to find, but with your expertise and direction I was able to locate it.  Just as you stated, I made a slight adjustment and all is good.


Thanks so much, your help is greatly appreciated!

[KaPH33n]

Great news! I love an easy fix. We’re you able to adjust the green as well?


Enjoy your game, it’s a wonderful, classic Atari game. Probably one of the best trackball games of all time.

[milricky]

Yes.  I was able to adjust the color and the brightness and improve the image.  Thanks again for you help!