please help me with my Ms. Pac madness..

vintagegamer

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Hopefully someone can help provide some insight on this on-going Ms. Pac issue:

I have a Ms. Pac machine that played blind when I got it (tube neck was busted). I got a working tube and put it in, and had the monitor chassis rebuilt.

I hooked up the game with the new monitor chassis and tube, and the board stopped working. I sent the board off and it needed repair, it has been repaired and tested and is supposedly working fine. Upon install of the board, I'm just getting a black screen. The monitor is getting 122V AC according to my DMM.

I checked the caps at C2 and C3 on the board while the game was powered up, and they are only reading 2.5V. Bungy was down over the weekend and looked at the machine with me, and said the edge connector looked fine, and he checked voltages at the connector and they appeared to be fine.

I have a switcher supply for the board, but when I hook it up it blows all 4 fuses on the right-side fuse holder (2 fuses are 1A, 2 are 5A). I replaced the fuse holder a few months ago and the problems mentioned above still persist. The switcher board will only go in one-way, so I'm certain I am not hooking it up backwards.

I'm not sure how else to troubleshoot the issues this machine is having, which surprises me because I thought Ms. Pac's were pretty simple in design and troubleshooting. My questions are:

1. could it be the power brick itself?
2. is there a way that I can wire up the switcher to bypass the power brick completely, just to see if that's the issue?
3. what other troubleshooting can I do?
4. will providing a pic of the power brick help anyone here in diagnosing?
 
Personally, I wouldn't put a switcher in there, the power bricks in Ms. Pac man's work GREAT. Do this, take your multimeter, and check the voltage, a/c, between the top two fuses, on the right side of the fuse holder. Then, take your multimeter and check the voltage between the bottom two fuses, on the right side of the fuse holders.

So red probe to top fuse right side, black probe to fuse below it, right side. See what it says, then repeat with the other two. This will tell you if your power supply is fine, which I'll bet money it's right on unless you've got some wiring issues.
 
Personally, I wouldn't put a switcher in there, the power bricks in Ms. Pac man's work GREAT. Do this, take your multimeter, and check the voltage, a/c, between the top two fuses, on the right side of the fuse holder. Then, take your multimeter and check the voltage between the bottom two fuses, on the right side of the fuse holders.

So red probe to top fuse right side, black probe to fuse below it, right side. See what it says, then repeat with the other two. This will tell you if your power supply is fine, which I'll bet money it's right on unless you've got some wiring issues.

Thank you LA, I will check that out tonight.
 
Personally, I wouldn't put a switcher in there, the power bricks in Ms. Pac man's work GREAT. Do this, take your multimeter, and check the voltage, a/c, between the top two fuses, on the right side of the fuse holder. Then, take your multimeter and check the voltage between the bottom two fuses, on the right side of the fuse holders.

So red probe to top fuse right side, black probe to fuse below it, right side. See what it says, then repeat with the other two. This will tell you if your power supply is fine, which I'll bet money it's right on unless you've got some wiring issues.

ok so the reading on the first pair is 24.5v ac. The reading on the 2nd pair is 14.4v ac. Is that good or bad? also, that is the 'new' fuse holder.
 
ok so the reading on the first pair is 24.5v ac. The reading on the 2nd pair is 14.4v ac. Is that good or bad? also, that is the 'new' fuse holder.

Yes, that is good. Each of the first two fuses should carry 12vac and each of the second two should carry 7vac.

That is why I was stumped. Voltages are good but the game does not play. You should really try that board in another Ms Pac to know for sure whether it works. If you are too wary of using your other Ms Pac, you can always bring it up here and try it in my Pac cabinet.
 
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Yes, that is good. Each of the first two fuses should carry 12vac and each of the second two should carry 7vac.

That is why I was stumped. Voltages are good but the game does not play. You should really try that board in another Ms Pac to know for sure whether it works. If you are too wary of using your other Ms Pac, you can always bring it up here and try it in my Pac cabinet.

argh then why would it have worked fine in channelmanic's machine? i swear there must be a magnetic field near my house or something. :( and like i mentioned when u were here, my other ms pac came from coney island and is wired up like a teen boy's car stereo- if i pull anything out of that machine even for 2 secs, i'll have 2 dead ms. Pac's! 'why doesn't anyone listen to me??'-c3po
 
Maybe the board was damaged in shipping. Your power supply is fine though, don't mess with the switcher and that stuff, you'll just make it worse.

Do you not get ANYTHING on the monitor? Usually a pac board will do something, show garbage, reset, make the coin meter click, something.

You say you only get 2.5 volts at the caps; have you checked the two diodes right there with a meter? Does your meter have a diode check function? It's the two large power ones about in the middle of the upper part of the board. You can't miss them; they'll be the ones burnt all to hell.
 
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Read the voltage as it's coming into the board at the edge connector.

If the AC voltage is good there then ship it back to me and I'll put it back on the bench. I'll even pay return shipping.

If it's not good there then check the wiring harness and the edge connector on the harness.

RJ
 
Bungy checked the voltages for me at the edge connector and said all looked good.

I will check the diodes as LyonsArcade has suggested and will report back.

I also want to note for the record that I don't think it in any way is due to any lack of checking on RJ's part. He was very informative through the whole transaction of the board swap, and packed the board to the point where I felt like I'd ordered it direct from an electronics store! I don't want this thread to tarnish his reputation in any way. It's OK if Bungy's gets tarnished though (Bungy knows me so he knows I'm kidding when I say that).

:D
 
Don't see any burned diodes. Caps at columns 8 and 9 read 8.3 v. Cap at c3 reads 2.5v. Cap at c2 reads 2.5v. Cap at c5 reads 10.5v. Cap at c10 reads 8.1v. No clue how to test voltage at edge connector. Is there really nothing else i can do to check this board in my own home? this is insane. Just want the thing to work.
 
There is one thing, and it's glaringly obvious :)

if you are talking abt dropping the pcb into my other ms pac, i keep trying to splain to you that it's not that simple. I can show u tonite when u come down to fix my Tempest LOL
 
CRAP!!!!!!!!!!!! I think I may have figured out what my switching supply problem is...

Could uh, someone please uh, post a pic of uh, what the Ms. Pac switcher edge connector adapter looks like? I currently cannot see the ArcadeShop site..
 
This?

attachment.php
 

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Ah well, was hoping maybe I'd solved my mystery. I know I have ordered more than one switcher from ArcadeShop, was hoping maybe the one I had at home was the wrong one for that machine. Wife confirmed for me that I have the right one, so I have no clue why it doesn't work.

Wrote to Steven at AS to see if he's ever seen one of those supplies blow fuses in the transformer brick before. Guess that's as far as I can go on this for now. :(
 
Don't see any burned diodes. Caps at columns 8 and 9 read 8.3 v. Cap at c3 reads 2.5v. Cap at c2 reads 2.5v. Cap at c5 reads 10.5v. Cap at c10 reads 8.1v. No clue how to test voltage at edge connector. Is there really nothing else i can do to check this board in my own home? this is insane. Just want the thing to work.

Found the below update:

"Low Voltage 2~3 VDC when measured at C2 or C3. Resistor R53 4 Ohm 10 Watt gets warm. Measured Voltage from Ground to the Base pin of Q6 ( D44MV4 on the big heat sink, may also be a TIP 31 or ECG 377) Shows ~ 8 VDC.

fix: Replace D44VM4. Be sure to install mica insulation & plastic sleeve on the the bolt too.

~ Note the pins on Q6 are marked on the board or refering to the above picture top to bottom

B) ase
C) ollector
E) mitter "


Source: http://web.archive.org/web/20050228090057/http://users.erols.com/mowerman/pacfile.htm

I have no clue what D44VM4 is, guess I'll be trying to figure that out tonight though..
 
Found the below update:

"Low Voltage 2~3 VDC when measured at C2 or C3. Resistor R53 4 Ohm 10 Watt gets warm. Measured Voltage from Ground to the Base pin of Q6 ( D44MV4 on the big heat sink, may also be a TIP 31 or ECG 377) Shows ~ 8 VDC.

fix: Replace D44VM4. Be sure to install mica insulation & plastic sleeve on the the bolt too.

~ Note the pins on Q6 are marked on the board or refering to the above picture top to bottom

B) ase
C) ollector
E) mitter "


Source: http://web.archive.org/web/20050228090057/http://users.erols.com/mowerman/pacfile.htm

I have no clue what D44VM4 is, guess I'll be trying to figure that out tonight though..

ok i found this part am i able to check it w a dmm?
 
Here's the little bugger that could be causing me my pain..
 

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