Ms. Pac Man cocktail. Bad power?

darthphunk

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Hey guys.

I have a Ms. Pac Man cocktail cabinet that I picked up a few months ago. When I first got it, I powered it on and I get streaks on the monitor and a high pitch squeal from the monitor... exactly like the 3rd pic down in the right column here...

http://www.arcadegameover.com/pactrouble.html

"Fast moving short vertical lines covering screen. High pitch squeal from monitor. Caused by shorting 6 MHz clock signal to other chip pins. Also caused by PCB frequencey pot not adjusted"

I checked the fuses, and 4 were bad/blown. I replaced all of the fuses (just to be sure) and I got the same issue. I'm new to restoring cabs, so I sent the PCB off to have it tested. The person who tested it says it works just fine and sent it back.

Could this problem be because of a bad power supply? Both blocks look pretty ratty. I know they are pretty indestructible... but I suspect that one or both may be the issue.

I'm thinking of picking up a swotching PS conversion kit from here:

http://www.arcadeshop.com/parts.htm#Power

Am I on the right track? Is there anything else to check?

Thanks in advance for your help.
 
well, the first thing to check is that you actually have bad power by measuring it at the edge connector. Bear in mind that it is AC power, so you'll need to test between the proper points to get a correct reading. If you have bad power, then a switching power supply upgrade is probably your best bet.

Once you know you have good power, you need to check the connector to the board, as a lot of problems can be traced to bad edge connectors. Sometimes you can verify this is the problem by wiggling or flxing it a bit and seeing the game boot up fine. If this is your problem, you can replace just the connector or the entire wiring harness as you see fit...
 
well, the first thing to check is that you actually have bad power by measuring it at the edge connector. Bear in mind that it is AC power, so you'll need to test between the proper points to get a correct reading. If you have bad power, then a switching power supply upgrade is probably your best bet.

Once you know you have good power, you need to check the connector to the board, as a lot of problems can be traced to bad edge connectors. Sometimes you can verify this is the problem by wiggling or flxing it a bit and seeing the game boot up fine. If this is your problem, you can replace just the connector or the entire wiring harness as you see fit...

Thanks for the advice. It sounds like I am on the right track.

Again, I'm new at this and can use my meter to test fuses, but that's about the extent of my knowledge there.

Do you know which pins on the edge connector I need to check, or where I can find out how to do that?

And as far as my meter settings... I need to set it to V~ 200... and I am assuming I am looking for a 12v reading?

Thanks!
 
When I get home, I'll get you a link to a game manual if someone doesn't beat me to it. You;ll find a wiring diagram inside that shows where the power comes from the transformer to the edge connector at the game PCB, and what color wires they are.....
 
When I get home, I'll get you a link to a game manual if someone doesn't beat me to it. You;ll find a wiring diagram inside that shows where the power comes from the transformer to the edge connector at the game PCB, and what color wires they are.....

I have the manual printed out somewhere. I obviously haven't thumbed through it yet :) So if it's too much trouble, don't worry about it.

Am I on track with how I should set my meter?
 
Yes. Just find the 7vac inputs and measure there. That will be converted to +5 vdc on the board for your board to work (the other voltages are for sound). As we know your board works fine, then the DC conversion works, so we just need to check the inputs...
 
Are you sure it's not just a monitor problem? The high pitch squeal and lines is usually caused by the horizontal hold/sync being out of whack.

-Ian
 
Are you sure it's not just a monitor problem? The high pitch squeal and lines is usually caused by the horizontal hold/sync being out of whack.

-Ian

I'm fairly sure.

I can't play it blind and I get no sound from the speakers when adding credits. I suppose I'll find out when I hook it up without the PCB connected.
 
Sometimes a monitor will squeel if no input is hooked up. How does the edge connector look on it? If its got a filter board yank it out.
Dont bother measuring the AC, check across cap C3 for +5vdc. If its got it your good on the power, if not then you can backtrack and check the ac side. Replace those fuse holders if they are original and make sure you install the right size fuses.
If all 4 fuses were blown then someone probably plugged the edge connector in backwards. Usually a problem on the board will only take out one pair of the fuses.
 
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