Original Ms. PacMan cockatil fried (montor?)- help to fix/upgrade(?)..

Awesome! I'm glad it worked out... hopefully you learned something along the way too!

DogP
 
Aaarrrgg

So it actually *is* still re-booting.. It just takes a long time for it to happen after first turning the machine on from cold- 20-30 minutes. After that the time between re-boots shortens the longer the machine stays on:(

From what I could see everything on the bottom of the monitor PCB is in good shape, but the problem *seems* to be on there since that is where something 'ticks' when it reboots and it happens with either game pcb installed.
 
Toying with the idea of finding another monitor PCB to swap out- I found someone selling rebuilt ones on ebay- same model as this one, but they are missing this metal shield (see pic).. Is this shield likely specific to the ms pacman use, or would it be standard for the monitor?
 

Attachments

  • component_shield.jpg
    component_shield.jpg
    164.2 KB · Views: 14
That metal shield isn't specific to your Ms. Pac, but is sometimes missing because someone will remove it to replace the caps under it, and not put it back. It's not critical, but it's a good idea to have to prevent possible interference.

DogP
 
Oh, and does the game actually reboot, or does the monitor just go dark and then come back. Did you make sure your anode is properly seated in the tube (both prongs in the hole in the tube)?

When looking for arcs, I find it's best to turn the lights out and stare at the back of the monitor... it should be really easy to spot in the dark. You can also look at the metal (usually near the flyback) for burn marks where the spark is arcing to.

DogP
 
Oh, and does the game actually reboot, or does the monitor just go dark and then come back. Did you make sure your anode is properly seated in the tube (both prongs in the hole in the tube)?

When looking for arcs, I find it's best to turn the lights out and stare at the back of the monitor... it should be really easy to spot in the dark. You can also look at the metal (usually near the flyback) for burn marks where the spark is arcing to.

DogP

It does fully reboot- screen goes through all of the test patterns and stuff as though I had suddenly removed/reapplied power to game.

Good call on the lights out- I will try that. I recall running into this reboot issue intermittently *before* the flyback exploded a couple years ago- unfortunately the flyback explosion seems to have comletely covered the top of the board anywhere near it with blackness (the smoke from it's explosion?).

There is no stopping me at this point ;)
 
It does seem strange that the monitor would cause a reboot of the game board... did you make sure that your grounds are attached to the monitor frame and everything?

Another test that would be worthwhile is to unplug the monitor and make sure it doesn't reboot (obviously you'd have to listen to the game sounds rather than watch the screen). It's possible that there's a problem with the transformer in the bottom of your cabinet or something.

DogP
 
It does seem strange that the monitor would cause a reboot of the game board... did you make sure that your grounds are attached to the monitor frame and everything?

Another test that would be worthwhile is to unplug the monitor and make sure it doesn't reboot (obviously you'd have to listen to the game sounds rather than watch the screen). It's possible that there's a problem with the transformer in the bottom of your cabinet or something.

DogP

I guess I can unplug the monitor, drop in a ton of credits and try and keep game sounds going and see if it reboots that way.. or maybe if I just crank of the volume there might be some variation in the hum when it reboots..

I never removed any wires that went from the monitor to the frame and what's there seems intact and fastened well. Could I be missing a wire? I can post a pic when I get home..
 
I unplugged just the monitor power cable, turned on the game and put 12 credits in. I started one about every twenty minutes an after about 4 hours got through all of them. So seems like the problem is either on the monitor, or some combination between monitor and cabinet.

The only wires (grounding?) between the monitor and cabinet/metal are the pair of white ines that wrap around the tube. There is also the grounding wire (yellow w/green stripes) coming from the cabinet PS that attaches to the monitor frame metal. And there is the black wire that goes from a metal strap on the back of the CRT tube to a pin on the yoke board.

The monitor board in the vicinity of the fly back is basically covered with greasy looking black residue (soot from fly back explosion?). Also the copper coil part (I forget what it's called/for) is broken (missing top half of white plastic part- not sure if that was also flyback fallout or was that way for longer) but I thought that was just to support the coils..pics attached...
 

Attachments

  • IMG_1799.jpg
    IMG_1799.jpg
    197.5 KB · Views: 14
  • IMG_1800.jpg
    IMG_1800.jpg
    191.4 KB · Views: 12
Last edited:
Okay, yeah... it sounds like the monitor is causing it, and it looks like it's grounded properly (tube to the neckboard, and the clip circled in yellow to the frame). The other picture is the width coil, and yeah, that shouldn't be causing any problem (there's supposed to be a piece of plastic with a movable ferrite core to adjust the width, but without it, it'll just be adjusted to the maximum width).

So yeah... the places I'd watch closely are the near the flyback (and adjustment assembly), the neckboard, and the anode cup (HV wire to the tube). Those are the places with the >1KV voltages... everwhere else is relatively low voltage (<200V) and less likely to randomly arc.

Oh, and the white wires that wrap around the tube are actually the degaussing coil. Those (hopefully) aren't grounded.

DogP
 
Last edited:
I wasn't able to spot the arc- I need to try at night (I can't get the room dark enough during the day). I tried swapping in a 'new' monitor board, and sure enough it runs fine.. Which is going to make it tough for me put in the effort of swapping the old one back in to debug this arcing issue- though I did go through all the effort to re-cap and flyback the old one- so I'll get to it!

One thing I noticed using the new monitor board- the horizontal centering has the score numbers just barely kissing the edge of the screen- and there is still a good amount of screen space below the credits. I tried moving the H-center wire onto the other two pins- but the both put the numbers further (partially off) the side of the screen... I don't need to mess with width- is there anything else on the board that is adjustable for horizontal cenetring?

This is how it looks now- totally playable- but enough to nag a compulsive person;)
 

Attachments

  • IMG_1851.JPG
    IMG_1851.JPG
    177.9 KB · Views: 16
  • IMG_1852.jpg
    IMG_1852.jpg
    168.7 KB · Views: 17
You can move it a bit using the H-Freq pot... if you go too far, the edge of the image will start to curl, so just watch for that.

DogP
 
Restricting this thread :( ..

The machine worked great for a couple of years after all the work we did based on this thread.. Then it was left un-plugged up until now (4 years later). My daighter asked me if we could play it last week and when I plugged it in I got the cabinet lights and fan, but no monitor or audio- ie nothing screen-wise and no audio cues that the game was operating (no sounds registering coin drops- tried adjusting the volume pot).

What is the most basic first thing I should check? My guess is something power related to the game mainboard- but I don't know where to start..

I love this machine and want to try to keep it functioning in all of it's original analog glory!
 
Definitely check power... in particular I'd check the fuses/fuse holders and edge connector. They tend to get dirty/oxidized and need to be cleaned, and also sometimes simply wear out (pins lose their "springiness").

I quickly scanned the thread, and it looks like you still have the original transformer, not a switching power supply, so you should have 7V AC (pins 3/C and 4/D) and 12V AC (pins 19/W and 20/X) going into the game PCB, which is rectified to DC on the board. Each of those AC lines has a fuse in-line (5A fuses for 7V and 1A fuses for 12V). You can use a multimeter to check AC at various points (transformer, fuse holders, edge connector, etc)... or you can start by looking for +5V DC at the game PCB, and if that's not present, work your way backwards.

DogP
 
Definitely check power... in particular I'd check the fuses/fuse holders and edge connector. They tend to get dirty/oxidized and need to be cleaned, and also sometimes simply wear out (pins lose their "springiness").

I quickly scanned the thread, and it looks like you still have the original transformer, not a switching power supply, so you should have 7V AC (pins 3/C and 4/D) and 12V AC (pins 19/W and 20/X) going into the game PCB, which is rectified to DC on the board. Each of those AC lines has a fuse in-line (5A fuses for 7V and 1A fuses for 12V). You can use a multimeter to check AC at various points (transformer, fuse holders, edge connector, etc)... or you can start by looking for +5V DC at the game PCB, and if that's not present, work your way backwards.

DogP
Awesome- I will bust out the multi meter and get to work- thanks!
 
Awesome- I will bust out the multi meter and get to work- thanks!
Ok this is nuts- resurrecting this again- I never actually got to testing stuff from that last post- work/kids/everything just got too busy..

But I am getting to it now!!

So I just tested the fuses, and the two 12V 1A fuses were both blown... So I grabbed more at HD and after replacing them, the two new ones both blow immediately after powering on the machine. All other fuses are fine..

Also I tried putting in good new 12V 1A fuses and disconnecting the edge connector before powering on and they didn't blow in that cases- so it looks like back to something on the board.

What where do I need to start looking for a short that would be blasting those fuses?

(I can also say that when powered on with the two 12V 1A fuses blown- if I turn the brightnes up on the monitor I can get the screen close to white so the monitor is still working fine)
 
Last edited:
Ok this is nuts- resurrecting this again- I never actually got to testing stuff from that last post- work/kids/everything just got too busy..

But I am getting to it now!!

So I just tested the fuses, and the two 12V 1A fuses were both blown... So I grabbed more at HD and after replacing them, the two new ones both blow immediately after powering on the machine. All other fuses are fine..

Also I tried putting in good new 12V 1A fuses and disconnecting the edge connector before powering on and they didn't blow in that cases- so it looks like back to something on the board.

What where do I need to start looking for a short that would be blasting those fuses?

(I can also say that when powered on with the two 12V 1A fuses blown- if I turn the brightnes up on the monitor I can get the screen close to white so the monitor is still working fine)
Pac-Man hardware takes in AC voltage at the board edge, the AC voltage is rectified to DC on the game board. so I would test the rectifier diodes on the +12V side (search for a board pinout if you don't know where this is) cause they're probably shorted. why they're shorted you'll probably have to dig a little deeper. I don't know how to test it for shorts accurately besides the "backwards" diode check with meter (red lead on ground, touch black lead to find junction drops), but the amplifier IC isn't pleasant to remove. the heatsink is plastered in multiple legs worth of solder to ground. I've found the LM1877N to be a great replacement because it doesn't run monumentally hot and from hours of running a Ms. Pac-Man with it, I didn't find it needed the heatsink anymore.

while you're in there, these games are very old now and it's effectively mandatory to replace the caps on the game board.

hopefully you can figure it out. I also don't know the diode part numbers but you can probably find them in the game manual.
 
Thanks
Pac-Man hardware takes in AC voltage at the board edge, the AC voltage is rectified to DC on the game board. so I would test the rectifier diodes on the +12V side (search for a board pinout if you don't know where this is) cause they're probably shorted. why they're shorted you'll probably have to dig a little deeper. I don't know how to test it for shorts accurately besides the "backwards" diode check with meter (red lead on ground, touch black lead to find junction drops), but the amplifier IC isn't pleasant to remove. the heatsink is plastered in multiple legs worth of solder to ground. I've found the LM1877N to be a great replacement because it doesn't run monumentally hot and from hours of running a Ms. Pac-Man with it, I didn't find it needed the heatsink anymore.

while you're in there, these games are very old now and it's effectively mandatory to replace the caps on the game board.

hopefully you can figure it out. I also don't know the diode part numbers but you can probably find them in the game manual.
Thanks for the plan of attack- given how much of an oddysey it was for me to complete the multiple repairs needed to the game board and monitor myself last time with just my soldering iron, multi-meter, no real bench setup to work on (just the machine itself), and how much free time I have now, I just sort of gave in and sent the board to @madrits to repair :/ .
 
Thanks

Thanks for the plan of attack- given how much of an oddysey it was for me to complete the multiple repairs needed to the game board and monitor myself last time with just my soldering iron, multi-meter, no real bench setup to work on (just the machine itself), and how much free time I have now, I just sort of gave in and sent the board to @madrits to repair :/ .
@madrits is great

I didn't reach the level I'm at on my first project ever, it's something you build up to over time. no shame in asking for help.
 
Back
Top Bottom