Help getting a Ms Pac Man Board working

zinkatres

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Hello all. I am helping out a buddy to try and get his ms pac man arcade game working. The previous owner said it was working (but had to wiggle the rf board once in while to get it going) However, when we got it, it was not working at all . I was able to get it to finally power on after removing the rf filter board and some new fuses.

But now when it is on we just get a screen of garbage and a constant clicking noise of some sort. I looked up a few posts and the screen looked similar to some I saw which said the sync bus board was damaged/not detected. I tried re-seating it with no change. If I remove the sync bus board all together the clicking stops and the unit remains on.
Thinking that was the issue we got a second sync bus board, but the problem persists.

My next thought was to replace the socket for that board. While I was doing that I thought I would check and see if there was anything else I should check out or go ahead and replace.

The machine is not at my place, so I can get additional information if needed, but it may be a little slow for him to relay it to me. I have attached an over all picture of the board he sent me as well as what the garbage screen we are getting looks like.

Hopefully someone with a little more knowledge can help us out. Thanks in advance!
 

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Z80 socket, could be. could also be the ribbon cable though. that's what's happened in my experiences with Ms. Pac.

there's a test you can perform to rule that out, unplug the Z80 from the daughterboard, then unplug the ribbon cable, plug the Z80 where the ribbon cable was. I should say, it COULD be the ribbon cable, but it could be the socket on the daughterboard for the CPU too/instead, but probably not likely. the ribbon is essentially a mechanical device, it can wear out.

we're dealing with stuff that's over 35 years old. it's a miracle they lasted as long as they did.

doing the Z80 swap though, you should have Pac-Man with funny looking Ms. Pac sprites. you can verify then that your main board is good. :)

for other preventative maintenance, I encourage replacing the fuse holders in the bottom. the old ones are old, you can lose power across them, which is bad for the main board.
 
So the Sync Bus Controller is probably okay and the issue is probably with the ribbon cable, its sockets, or the aux board to the side of the main board?
 
You're missing a circuit board at the end of that ribbon cable. That small circuit board holds the ROMs and the Z80 CPU for Ms Pac Man.
 
I just realized that the z80 board was not in the picture. But it is there, still attached to the cabinet
 
have to replace the fuse holder(and new fuse) in the bottom of the cabinet. this is MANDATORY

the wiring harness connector there has given me problems.
gently, very gently, move the wiring harness just a little bit and see if that clears up the image on the screen.
those pins in there can be weak and the wiring harness is not attached to the cabinet very well above the connector there. I like to move the connector/wire harness into a "relaxed" position there where it comes out of the game board

many I have seen the wire harness has moved and putting "torque" on the connector and the weight of the wires can be moved into a more "relaxed" position there above the connector. sometimes an extra staple into the wood with a wire tie can fix up the wire harness so it holds there better

hope the sync bus board gets figured out but please replace the fuse holder as that is a common failure point.

good luck
 
All great ideas and advice.
I just went through 250 installs in about a week...I still stick to the z80 and it's sockets. :)
 
Thanks for all the advice guys. I got some new sockets (and a new z80, just in case) on order.

I will check those out and see what kind of shape we are in after replacement. If that can straighten it out with those, then we will move on to the fuse holders, edge connector and such.

I will report back soon, thanks again
 
Just a side note.. sometimes it a good thing to let people know your location.

Sometimes a local collectors will help you isolate your problems and might even have spare parts.
 
That's a good thought, Alpha-tron, I am located in Effingham, IL


A quick status update for everyone. I replaced the sync bus socket, the ribbon cable to the aux board and replaced the Z80, also touched up the solder joints on the ribbon sockets. After that we were able to get a working and playable game.

Now that the game is playing we are noticing a hum bar on the screen and a loud audible hum in addition to the games sounds through the speaker

On my list to change still are the fuse blocks. I also thought about replacing the power supply with something like this:
http://v2.globalwebcart.com/arcadeshop/i/932/midway-power-supply-kit-3.htm

What would everyone's next step be?
 

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Hi guys, back with an update. I replaced the 4 slot fuse block this evening on the Ms PacMan, and while the hum bar on the screen seems to have been cured I am still left with a loud audible hum through the speaker.

Here is a short video clip I took (prior to replacing the fuse block) if it helps to pinpoint the issue any.

http://bit.ly/2lTCNSY

Other things I have done:
1. Tried a different speaker
2. unplugged both the coin door and the marque light while running
3. verified good voltage coming from the transformer and passing through the fuse
4. cleaned the edge connector and harness, as well as a visual inspection. Appears to be making a solid connection.

Do I have a problem with the sound circuit or the AC to DC circuit? What do we think is the next place to look? Thanks!
 
I'm not getting any sound with that video...

Check the 2 diodes that rectify the AC into DC. They aren't the 2 big ones near the heat sink, but 2 smaller ones over towards the audio section but still near the edge connector. One of those is probably leaky. Could also be a bad cap in the audio section.
 
Hey everyone, just wanted to jump back in and let everyone know where I was at with this board and what all I have done since my last post.

As of right now we have still not solved our audio hum

For a test I took the board out of our pac man cab and put it in the ms pac cab. It worked fine with no audio buzz. I would think this confirms that our problem is still on the ms pac board and not in the cabinet, transformers, or harness wiring.

So on the board I have replaced all the capacitors as well as the D3/D4 and D7/D8 diodes


Do you think my sound chip may be bad? I have a replacement LM1877 chip that I got just in case

Otherwise I don't see anything visually that raises any alarms. What do we think my next step should be?

Thanks again!
 
Hey everyone, just wanted to jump back in and let everyone know where I was at with this board and what all I have done since my last post.

As of right now we have still not solved our audio hum

For a test I took the board out of our pac man cab and put it in the ms pac cab. It worked fine with no audio buzz. What do we think my next step should be?

Thanks again!

Try the opposite - put the Ms Pac board in the Pac cab and see if the hum follows the board.
 
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