Ms Pac Man Blows Fuse when trying to power

bkctonight

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Hi all.

My Ms Pac Man machine continues to blow the Line fuse (currently 2 amp) everytime I power my cabinet machine. My on/off switch on top of arcade is good. My kill switch on the inside is good (keeping it in the up position so that the circuit is always connected). But as soon as I place a new 2 amp fuse and plug in the machine (every button and/or switch on the on position), the fuse blows. How much voltage should be running through that fuse? I am pretty sure my fuse amperage is right at 2 amps. I am really stumped here. I have followed the volts using my meter all the way from the ac power cable (wall plug) to the amp clamp and I am reading about 120 volts.

Any help or advice would be great.

Thanks.
 
Actually, unplug the board, coin door, marquee, monitor - then power up and see if the fuse blows. If it doesn't, then plug each item in one at a time until the fuse blows....
 
Unplug the marquee light fixture first and see if the fuse blows. The light fixture could have a shorted ballast.
 
I would do like Mod said but also agree with Ken that the marquee light is probably the guilty party here.
2A is right, are you using a slow blow fuse? Depending which main fuse it is, could also be the one for the ISO trans so unplug the monitor too.
 
I unplugged the monitor, the marquee light, and the coin slot. The fuse is still blowing as soon as I power on the machine. Thanks for your help guys.
 
Unplug the edge connector to the game board

Shouldnt be that, if it were the pcb the other 4 fuses would be blowing....unless they are severely over fused. Start inspecting the wiring starting at the power cord plug and work your way in. Look for any fraying that could be shorting.
Maybe someone hooked the wires up to the interlock switch wrong, that would be a dead short. Got a camera? Were going to need some pics.
 
I unplugged the monitor, the marquee light, and the coin slot. The fuse is still blowing as soon as I power on the machine. Thanks for your help guys.

as the others are saying, unplug the edge connector to the ms pacman PCB. i think it's the last thing your power supply is providing juice to.

if you plug is wired bad, you better be popping the outlet breaker.
 
Ms Pac Man

Guys,

Thanks for all the help. Still no success though. As requested I have attached some pictures that may help. I am leaning towards a faulty exterior switch. There are signs of buring on one of the switches electrodes.

Let me know if other pictures may help.

Thanks!
 

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  • Kill Switch.jpg
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Where are you measuring that 120? Did you unplug EVERYTHING, including that switcher, to make sure nothing is connected to the 120 line that might cause a short?
 
That's not a Ms Pacman anymore...

It's been rewired with a switching supply. Snap a picture of the board too so we can see if it's original. What's up with the missing fuse in that two-fuse block on the left? How about slip another one in there.

Also, is that some loose metal bracket in the bottom of the cab on the right? Make sure you don't have any foreign object like that touching any part of the supply in the cabinet.
 
I see the back door interlock (safety) switch is a bit beat up, but I don't think that's the problem. You should not be able to see anything inside that switch. Looks like part of the switch's plastic face has been torn off.

However, I do see a problem with the way that switching power supply is wired. Notice that the blue-gray wire going to one of the AC terminals on the power supply appears to be burnt? According to the Ms. Pacman upright schematics, if you're patching in a switching supply, you need to pickup the AC power for it from the blue-gray and black-red wires of the PRIMARY side of the isolation transformer. From the pictures, it is hard to tell if it's wired correctly. If the power supply is connected to the SECONDARY of the isolation transformer, that is wrong.
 
Reply

Modessitt: The 120 reading is from the empty fuse holder (this is the one that keeps blowing). I am reading the volts from the power supply side. Power is running from wall to kill switch to exterior switch to blowing fuse.

Kstillin: The empty fuse holder is because that's the fuse that keeps blowing. I have plenty of spares...believe me. The loose wires you see (i.e., green&yellow wire) are the grounds of either the monitor or marquee. There aren't any other loose items that should be connected to anything or touching anything connected.

Ken Layton: The kill switch is pretty beat up, but it's doing what it's supposed to do. I am not very familiar with the power supply wiring, but I will try to take a look at the schematics (which I have) and try to follow.

Thanks again folks! I know I am close to getting this puppy up and running again.
 
Did you disconnect the power leads to the switching power supply to make sure its not shorted and causing the fuse to blow? Make sure you insulate those wires with some tape before powering back up.
What type/rating fuse are you putting in it? Should be 2A slow blow.
 
Yes, you need to disconnect the power to the switcher, to the monitor, to the coin door, to the marquee, everything. Then put the fuse back in and see if it blows. If not, connect each thing one at a time, reapplying power after each one to see if it causes the fuse to blow. Once you know what is blowing the fuse, then you can fix it...
 
You might even take one of the input leads off the main transformer to rule that out too. A shorted transformer might have been the reason a switcher was added.
Not sure, have we verified if its the iso fuse or the main? I meant to take a look in one of my machines yesterday and forgot all about it.
I know a bad transformer is not likely but dont overlook anything. Its easy enough to desolder one of the terminals and rule it out for sure.
I would do it to both of the transformers. Better yet, since your not using the main transformer anymore I would remove the input power to it and leave it off. No sense powering up a transformer your not using.
This is frustrating, if we had the game in front of us its a 5 minute process to find the problem.
 
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