Original Ms. PacMan cockatil fried (montor?)- help to fix/upgrade(?)..

Holy cow- you are right- (I did hear a bbzzzww when first powering up), and twisting the bottom adjuster made the brightness come up- the monitor is definitely lighting up now.. Though there is no game image/sound or anything..

Now this is what's happening:

The 1A fuse on the inside most position of the 4 position fuse clip assembly at the bottom of the cabinet keeps blowing when the cabinet is powered on with no AC ground plug (3-2 prong adapter on AC cord at wall).. I originally had the game plugged in this way for years running from a non-grounded outlet. If I replace that 1A fuse with a good one, then plug the machine with all three prongs into a properly grounded outlet- then the entire cabinet will not power on in any way... If I go back to the un-grounded outlet situation the cabinet will power up, but that fuse blows..

I'm not sure what section that fuse is part of, but it sure seems like there is a short or something going on in that circuit..

I seriously appreciate all of your tips.
 
Lemme look at the manual in a sec... but just a quick thing. Did you take a good look inside the cabinet to make sure there aren't any stray pieces of anything where they shouldn't be? Maybe pieces of the flyback (the ferrite shouldn't cause problems), quarters/tokens, screws, etc.

From the factory, pretty much all metal pieces in the cabinet are grounded to the outlet ground, so something touching a piece of metal would blow the fuse if the ground is connected, but if it's not properly grounded, it may not (and instead could shock the person touching the cabinet).

DogP
 
Lemme look at the manual in a sec... but just a quick thing. Did you take a good look inside the cabinet to make sure there aren't any stray pieces of anything where they shouldn't be? Maybe pieces of the flyback (the ferrite shouldn't cause problems), quarters/tokens, screws, etc.

From the factory, pretty much all metal pieces in the cabinet are grounded to the outlet ground, so something touching a piece of metal would blow the fuse if the ground is connected, but if it's not properly grounded, it may not (and instead could shock the person touching the cabinet).

DogP

I can't find any loose metal or parts any part of the boards or anything touching any metal..

To clarify- if I plug the machine in with the ground connected the entire cabinet will not even power on- if I then just remove the ground the machine powers up.. That is the case with or without that fuse installed. The fuse just blows, if installed, when powered up with no ground connection.

I think I was clear about which fuse- but here is a pic (the empty holder)..
 

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Oh... interesting! Is the plug/cable original, or has it been replaced? It sounds like maybe the hot/neutral/ground may not be wired properly? I'm trying to imagine what would cause the machine to simply not power up if plugged in grounded (but not blow your house breaker or something), but work without a ground.

Regarding the blowing fuse... that runs 12VAC, which gets turned into 16VDC to run the audio amplifier, and also control the +5V regulator to run the logic. The fuse next to it doesn't blow? Can you tell me what the wire color is that goes to the fuse (should be Black/White or Blue/Yellow I believe)?

Try unhooking the connector from the game PCB, replace the fuse, and see if it still blows the fuse. There shouldn't be anything else connected to that, unless the wire is frayed and shorting to something.

DogP
 
The main power cord was cut and then tied back together to a new plug at some point before I got it (someone tried to lengthen the cord?) so I suppose wires could be getting mixed up in there. I went through all five of my new 1A fuses getting this far so I willl need to run out tomorrow to get more to continue debugging. The next fuse over does *not* blow. Rubbing away the dust on the wires- it looks like blue/yellow (see pic).

Yeah- the ground thing is WEIRD
 

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Yeah, I'd definitely double-check the wiring of the power cord. On the original cord, I believe the wire colors should be Brown=hot, Blue=neutral, Green/Yellow=ground.

Regarding the blowing fuse... when you get a replacement fuse, install it, remove the edge connector from the game PCB, and try turning it on. If the fuse doesn't blow, then there's an issue on the board. The first thing I would check is D3 and D4. They're 1N4004 diodes.

Not sure where you're grabbing the fuses from tomorrow, but a 1N4004 diode is one of the most common components out there, so you could check if they have one of them, and grab a couple while you're there, just in case. Radio Shack used to have them, Microcenter has them, and Fry's should have them (NTE116 is the equivalent NTE part).

You can test it by using the diode test on your multimeter (I assume you have one... if not, grab a cheap one like this harbor freight one: http://www.harborfreight.com/7-function-digital-multimeter-90899.html ).

You'll want to do the test with the edge connector disconnected. On diode test, touch the leads to opposite sides of D3. It should either read approximately 0.7V, or open. If you then touch the leads to the opposite sides, it should read open if the other way read 0.7V, or 0.7V if the other way read open. If it reads near 0 both ways, then the diode is likely shorted. Repeat the test for D4.

Like the caps, a diode needs to be installed the correct direction... so if you find a bad one and replace it with a new one, make sure to install it with the stripe pointing the same direction as the original.

DogP
 
I will be heading to Frys so I'll grab the components. Thanks for these super targeted instructions. After a full day at this I feel pretty invested to follow through with this fix now.
 
Cool, I know what you mean... though sometimes I think I should just cut my losses while I'm only 1 day into a project. ;)

DogP
 
Here is a pic of the way the power cord was patched- the game cord is coming from the left and the power cord going to the wall is on the right.. It looks like ground from the game goes to green/yellow on the cord- I assume that goes to the ground plug as you mentioned... Then it looks like the hot/neutral tie to brown/blue, or possibly vice-versa- I cannot tell- which is hot/neutral on the game side (left)- what would happen if they were swapped?

Frankly what you see there was all wound up in a ton of electrical tape, not to mention there is some areas of bare copper on both lines within that mess- Maybe I should replace the cord entirely to be safe.. Is the molexy looking connecter that the power cord terminates at inside the cabinet (second pic) easy to reuse onto a new cord, or should I plan on a new connector?

The good(?) news is that when I remove the edge connector from the game board and turn on the game with a two prong plug (the condition under which it would power up but blow that fuse) the fuse no longer blows- so I am on to checking those diodes- I will report back in a bit..
 

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Ok D3 and D4 when tested with the edge connector disconnected both seem to be passing current correctly :(
 
Another thing that doesn't look so good is a bunch of wires connected directly to the game board connector, maybe soldered directly, with some king of melted goop (insulation?) around the area. You can see some scortching there as well- I don't know if that scortching has always been there- but the funky fixed connection has been that way ever since I've had it.

The only thing I know of that is non "standard" with this cabinet is that it had the sped up version of the game- I thought that was just a ROM thing?
 

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Here is a pic of the way the power cord was patched- the game cord is coming from the left and the power cord going to the wall is on the right.. It looks like ground from the game goes to green/yellow on the cord- I assume that goes to the ground plug as you mentioned... Then it looks like the hot/neutral tie to brown/blue, or possibly vice-versa- I cannot tell- which is hot/neutral on the game side (left)- what would happen if they were swapped?

Frankly what you see there was all wound up in a ton of electrical tape, not to mention there is some areas of bare copper on both lines within that mess- Maybe I should replace the cord entirely to be safe.. Is the molexy looking connecter that the power cord terminates at inside the cabinet (second pic) easy to reuse onto a new cord, or should I plan on a new connector?
It looks to me that hot and neutral may be wired backwards. If you look at the power cord, obviously there's the green ground in the middle... and then on each side of that there's one with a smooth outside edge, and one with a rippled outside edge. The brown wire at the Molex connector in your 2nd picture looks to go to the rippled side, but in your first picture it looks like brown on the extended wire goes to the smooth side (it's also possible that I just can't tell from the angle of the pictures).

If the original cord is long enough for you, and in decent shape... I'd just install a replacement plug on it, and throw away their "extended" cord. It looks like they did a pretty crappy job connecting it anyway. Just use something like: http://www.homedepot.com/p/Leviton-...-Grounding-Plug-Black-R50-3W101-00E/205165472 . Any hardware store should have them... even Wal*Mart has them. If you're not familiar with replacing a plug, here's a guide: https://www.thisoldhouse.com/more/how-to-replace-extension-cord-plug (I'm sure the internet has MANY others as well). Just make sure to connect whichever side goes to the brown wire inside the cabinet to the hot side of the new plug.

DogP
 
Final update on the grounding- I think the plug/grounding is actually all correct- The machine will power on now weather plugged in with two, or three prongs just fine.. I think I just mixed things up when I was debugging that last night and had the main power leads inside the cabinet disconnected when I was plugging into wall AC w/ground (durh!). And it has historically worked that way for me since the 90's.

The molex connector picture was a bad angle (here's a better one)- the rippled wire actually goes to the purplish wire inside the game and the smooth goes to brown. And as you saw the smooth goes to brown on the wall plug- so it's all kosher I think.

In any case that single 1A fuse still blows when powered on with edge connector connected.

I have the manual as well, but I don't really know how to read the wiring diagrams..
 

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A little more imagery, info about that weird custom hard-wiring to the edge connector..

There is a blue/red striped wire coming out of the 5th pin from the left (closest to cabinet wall) on the edge connector- it comes out and is connected through a metal ring clip (grounding type?) that is not screwed to anything- also the orange wire you see coming out from that connection goes back through a connector into another wire that is soldered back to that same edge pin location on the board... Judging by the look of the blue wire connectors in this mess matching the ones used on the power cord extension I'd guess this was all done by the same person (before me).

I do not know what the heck is going on with this modification... It's funny because when you slide the edge connector onto the board it actually cannot seat all the way down onto the edge with all of the hard connections, but it seems those hard connected wires are all being spliced back into the appropriate wires coming out of the connector.. just bonkers!?!

This may all be a red herring relating to the fuse blowing since the machine has always worked fine this way before the flyback death..
 

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Ok D3 and D4 when tested with the edge connector disconnected both seem to be passing current correctly :(
Interesting...

Another thing that doesn't look so good is a bunch of wires connected directly to the game board connector, maybe soldered directly, with some king of melted goop (insulation?) around the area. You can see some scortching there as well- I don't know if that scortching has always been there- but the funky fixed connection has been that way ever since I've had it.

The only thing I know of that is non "standard" with this cabinet is that it had the sped up version of the game- I thought that was just a ROM thing?
Woah... what a mess. It is pretty common for the PCB edge connector to get burned up, but that's a pretty ugly hackjob repair (I doubt that hot glue is gonna do any good holding things in place). This page shows a repair of a similar connector: http://www.therealbobroberts.net/pace.html . If it used to work, maybe you should just leave that alone for now though... those are the high current 7VAC pins, which get turned into 5VDC, which the game logic runs from.

If you get a chance... try measuring a few things.
1) With the board disconnected, measure the resistance between pin 19 and 21, also between pin 20 and 21. They should both be basically the same.
2) With the 1A fuse removed, and game board plugged back in, power the game on and measure the DC voltage across the striped side of D3 and GND (pins Y/Z/21/22 on the edge connector). Should be approximately 16V (or maybe not).
3) Also while running, measure the DC voltage across capacitor C2 or C3. It should be around 5V (or again, maybe not).

Just trying to get an idea of what is getting power and what isn't. I'm surprised that only one of those fuses is blowing... but with just one fuse blown, I believe it could still power the board.

And yeah, the speedup hack is just an updated ROM, so I doubt that has anything to do with your problems.

DogP
 

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Final update on the grounding- I think the plug/grounding is actually all correct- The machine will power on now weather plugged in with two, or three prongs just fine.. I think I just mixed things up when I was debugging that last night and had the main power leads inside the cabinet disconnected when I was plugging into wall AC w/ground (durh!). And it has historically worked that way for me since the 90's.
Ah... great!

I have the manual as well, but I don't really know how to read the wiring diagrams..
I'm using this manual as a reference: https://www.arcade-museum.com/manuals-videogames/M/MsPac-Man.pdf . Page 76 should be the wiring diagram that goes with your cabinet (middle says MS. PAC MAN CT).

The fuse that's blowing is the one coming off the 12V (AC) from the transformer, through the fuse, and into pin X and 20 on the BLU-Y (Blue/Yellow) wire. Following that to the schematic on page 78, on the left side you can see pin X and 20, which goes through a diode (D4) and meets up with the output from diode D3. That comes from the other 12V (AC) wire from the transformer (Black/White wire), which doesn't blow its fuse. The diodes rectify the AC into DC... it should still work (just not as well) if you only have half of it working, like when one fuse is blown.

There is a blue/red striped wire coming out of the 5th pin from the left (closest to cabinet wall) on the edge connector- it comes out and is connected through a metal ring clip (grounding type?) that is not screwed to anything-
Probably ran out of the other type of crimp pins, so they used a ring connector as a butt splice. :p

This may all be a red herring relating to the fuse blowing since the machine has always worked fine this way before the flyback death..
Yeah, I agree... I wouldn't mess with it too much, unless you're gonna redo the whole thing.

Along those same lines... do you know whether the fuse blew after the flyback went, or is it possible that the fuse has been blown for a long time?

DogP
 
1) 7.68 across 19/21, 7.88 across 20/21 (machine is off)

2) with 1A fuse removed, game board plugged in, machine powered on- DC voltage across the striped side of D3 and GND is 0.75V

3) DC voltage accross the capacitor you pictures is 2.0V
 
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Ah... great!

Along those same lines... do you know whether the fuse blew after the flyback went, or is it possible that the fuse has been blown for a long time?

DogP

If the machine could have appeared to be working fine without that fuse, then I have no idea when it might have blown. But for the record everything seemed to work well before the flyback, including audio..
 
1) 7.68 across 19/21, 7.88 across 20/21 (machine is off)

2) with 1A fuse removed, game board plugged in, machine powered on- DC voltage across the striped side of D3 and GND is 0.75V

3) DC voltage accross the capacitor you pictures is 2.0V
Okay... so it seems that 12VAC probably isn't making its way through. I think you actually ran test #1 that I wanted correctly the first time (open circuit)... I was just making sure that there wasn't a short or something between the 12VAC pins and GND on the board.

With the game powered up, can you measure the AC voltage across pins 19 and 21 (should be 12VAC) and pins 20 and 21 (likely 0VAC since the fuse is blown).

DogP
 
Okay... so it seems that 12VAC probably isn't making its way through. I think you actually ran test #1 that I wanted correctly the first time (open circuit)... I was just making sure that there wasn't a short or something between the 12VAC pins and GND on the board.

With the game powered up, can you measure the AC voltage across pins 19 and 21 (should be 12VAC) and pins 20 and 21 (likely 0VAC since the fuse is blown).

DogP

Measure with the connector on or off? I pushed the connector on a bit more firmly this time and I think both fuses are blowing now, or at least the second one just did- I could have slipped with the meter prongs and shorted across 19/20.. With the connector on now, and no 1A fuses in I am getting seemingly arbitrary voltages in th eneightborhood of 2-3V across 19/21 20/21... that seems impossible..

I'm pretty sure I am touching the stripes carefully with the meter tips..
 
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