Ms Pacman Resetting

boganvilla

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I've got a Ms Pac that was working fine but now keeps on resetting. At one stage it was resetting once you got to the second maze but now when you hit the 1 player start button it plays the intro music and then resets.
This happens with both of my Ms Pac PCB's one of which has already had the Riptor treatment and has had new eProms and sockets put on it.

I've been pretty thorough with this one and have done the following:
Replaced the 4 pos fuse block.
Replaced all 6 fuses with some new ones from Bob Roberts.
Cleaned the 2 pos fuse block.
Replaced the PCB edge connector (solder type).

All fuses meter out ok so are still good but after all this it still resets.
I want to rule out the power supply so as per lawnmowermans page Iv'e check all the voltages and have come up with this.

Voltages at the fuse holders
11.1 VAC
11.1 VAC
6.5 VAC
6.5 VAC

Voltage across C2 and C3 on the PCB.
5.08 VDC (c3)
5.06 VDC (c2)

Voltage across un-banded side of D7 and D8
12.9 VAC

Voltage across un-banded side of D3 and D4
22.3 VAC

Voltage from GND on edge connector to R52
12.7 VDC

Voltage from GND on edge connector to base of transistor on heatsink
5.9 VDC

Do all these voltages seem ok?
I'm a bit stumped as to what else could be causing this.
 
You say that it does it with two different boards, which means that it is a cabinet issue.

1. suspect bad or flaky safety interlock at back door.
2. suspect bowed back door making intermittent contact with safety interlock.
3. suspect loose back door making intermittent contact with safety interlock
 
I agree with Dokert!

Have you tried playing the game with the backdoor off and the interlock switch pulled out in the overide position? Some of the interlock switches are push/pull.

If you don't get any resets while doing that, check for a warped back door. You can always screw the back door in place - at least just to test the interlock switch theory.

If you still get resets, try replacing the interlock switch.

Good luck!
 
You say that it does it with two different boards, which means that it is a cabinet issue.

1. suspect bad or flaky safety interlock at back door.
2. suspect bowed back door making intermittent contact with safety interlock.
3. suspect loose back door making intermittent contact with safety interlock

Ok. So I didnt have a spare interlock switch so in the mean time I by passed it all together and it still resets.
Other things I tried:
Bypassed the on/off switch at the top of the cab.
Disconnected the coin door harness.
Disconnected the light fixture.

The time taken to reset seems to be getting shorter and shorter the more I try it. I'm starting to suspect that maybe both my Ms Pacman boards have a resetting issue.

Unless anyone else has some other ideas I'm going to make up a harness and plug the boards into my test bench and see how that goes.
 
I would suspect that your transformer is crapping out. Run the board off of a switcher and see if it still resets. I have recently had two Pacman machines that did the exact same thing, and both of them had failing transformers.
 
At any point in time do the ghosts move diagonal across the screen? Is it getting through the attract screen or partially through the attract screen before rebooting?
What speed are the eproms on row 6?
 
Ok. So I wired up a switcher and bingo. No more resets.

I do now have a monitor issue to fix ( vertical collapse) but I should be fine to do a bit of diagnosing in the vertical deflection circuit on this one.

Thanks for your help guys I really appreciate it.
 
Ok. So I wired up a switcher and bingo. No more resets.

I do now have a monitor issue to fix ( vertical collapse) but I should be fine to do a bit of diagnosing in the vertical deflection circuit on this one.

Thanks for your help guys I really appreciate it.

I don't know why, other than being over 30 years old but I am seeing quite a few Pac and Ms Pac transformers failing lately up in my area.
 
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