Ms. Pac Man Cocktail Lights

[wxforecaster]

It was tongue-in-cheek humor as my kids will find any excuse on a perfect 80 degree low humidity day to stay INDOORS.

OK, replacement of the fuse blocks is complete. What a difference. The old ones were completely oxidized with green. Continuity is very strong now.

Good news -- game play has returned. Nice crisp picture and sound, no artifacts whatsoever.
Bad news -- still no coin door/CP lights.

Facing the monitor, the voltages I'm getting off the 3 fuse block seem strange:

From left to right, on the transformer side of the fuse I'm getting:
32V
123V
62.5V

On the other side of the fuse block I'm getting:
19.6V
123V
62.5V

The 19.6V matches what I'm getting at each of the lamp sockets, and on the fuse block, is listed as 12V.

On the main transformer, the voltages all seem correct: 12.6V, 12.6V, 7.5V, 7.5V.

Evan

 

[RetroHacker]

Are you measuring the voltages correctly? Remember, this is AC. You don't put your black meter lead on ground. You're measuring across the output winding of the transformer.

For measuring the lamp sockets, you measure across the lamp socket - not one lead to ground and the other to the socket.

-Ian

 

[wxforecaster]

Apparently not I'll replace my alien tin foil hat with an idiot hat.

Measuring across each lamp socket I've got zero volts (as I would expect since they don't work).

Where do I put my leads to measure across the isolation transformer (which I assume is the top block in my picture on the previous page)? I was going off the instructions here http://www.arcaderepairtips.com/2010/06/09/checking-a-classic-power-supply/ which said to place the black lead on ground and then check each output. Maybe I missed something?

Evan

 

[RetroHacker]

Apparently not I'll replace my alien tin foil hat with an idiot hat.

Measuring across each lamp socket I've got zero volts (as I would expect since they don't work).

Ah hah! The truth comes out.

This circuit is incredibly simple. You probably have a wire off or broken somewhere. The coin door lights are powered by a winding on the isolation transformer (not the main transformer). Measure across that 12v winding at the transformer, and see what you get. Follow the wiring from the transformer, through the fuse, and to the coin door lights. You can use the continuity setting on the meter to check for breaks in the wire. Usually, coin door lights fail because at some point a wire got snagged or broken off due to the flexing from opening and closing the coin door.

-Ian

 

[wxforecaster]

I'm not sure what you mean by "across the 12V winding on the transformer). If I put my leads on the tabs on either side of the 12V fuse, I get 13.5V (that doesn't seem so bad). Why do I have a feeling this is still not the correct way to do this

I have continuity from the black wire coming off the transformer (across fuse to white/green wires) to all the coin door/control panel lamp socks.
I also have continuity to the adjacent yellow/black wires coming off the transformer.



-E

 

[mcandrewsoun]

if your seeing voltage across the fuse, then its possible the fuse is open... You should read 0 volts across the fuse.

 

[RetroHacker]

I'm not sure what you mean by "across the 12V winding on the transformer). If I put my leads on the tabs on either side of the 12V fuse, I get 13.5V (that doesn't seem so bad). Why do I have a feeling this is still not the correct way to do this

Yeah, that's not how you do it

And if you're reading 13.5v across the fuse, then you have something wrong. Measuring across the fuse should give you zero volts. Remember, the meter is showing you the difference in voltage between the two leads. If you've got a difference in voltage between one side of the fuse and the other....

Are you *sure* the fuse isn't blown? Pop it out and check it.

If the fuse is blown, then you probably have a short somewhere. Or, again, you could have a wire off that's touching the coin door, or something similar.

By "across the 12v winding of the transformer", I mean, check the voltage at the transformer, across the output terminals. Of course, if you're reading 13v, then it's working, the transformer is good.

Again, you need to check the wiring in the cabinet.

-Ian

 

[wxforecaster]

I assumed (idiot) the fuse was good because I had continuity across the fuse terminal and it looked fine. I could have sworn I tested all of them out of circuit but alas, it's a goner. I still have continuity across the terminal, even with the fuse removed. Duh....

Figures I have more than 50 slo-blos, but no 1 1/2A. Off to RS. Back in 10.

 

[wxforecaster]

OK, so clearly I got schooled in Alternating Current (so used to dealing with DC stuff).

New fuse = working lights!

This thread has been exhausting for you all I'm sure, but a few lessons learned:
1.) Because of the loop back, do not assume a fuse is good because there's continuity across the fuse block (in this case, there was continuity across the fuse block even with no fuse there!)
2.) There should be no voltage across the fuse block. This is what finally tripped the light bulb that the 1 1/2A slo-blo fuse WASN'T good.
3.) Test and retest the fuses out of circuit. I could have sworn I tested all 7 fuses when I took them out last night before the holder replacement, but obviously not. Mark them!
4.) Make sure you replace parts with the correct components (in my case the right wedge lamps).

Here is ultimately what I think went wrong.
1.) I didn't realize they were 12V lamp sockets and thus put #555's from my pinballs in there. Ultimately this blew the 1 1/2A fuse controlling the lamp sockets
2.) In reseating the fuses during my initial diagnosis, I inadvertantly broke the rest of the Ms Pac Man as the fuse holders were severely oxidized and the slightest movement of the other fuses caused several of them to lose metal contact. This would have ultimately created problems regardless. It cost me < $7 and a couple hours of uncomftorably leaning over the cocktail to replace all the fuse holders and solder in 14 wires.

So, now we have a nice clean, strong set of 7 fuse holders. We have working lamps and a perfectly working Ms. Pac Man cocktail.

I surely hope this summary helps others down the road on their way from noob-dom to expert technicians.

Thanks to everyone for bearing with me.

Evan

 

[RetroHacker]

Congratulations on getting it working!

-Ian

 

[Zork2]

One of the fuses on the transformer board assembly protects the CP lights AND the coin door lights. I'd bet you either have a blown fuse(doubtful) or a bad connection between the fuse holder and the fuse itself....those fuse blocks are known pains in the ass........
I can't remember which one it is off the top of my head, but it is a 1.5amp slow blow fuse.
I'm guessing that fuse just got lose when you moved it......

If only you would have listened to my first post you would have saved yourself a week of headache! congrats on figuring it out! Bet next time you have an issue with a ms pac coin door light, you'll know just what to do! How do you think WE know!?
And always always ALWAYS test a fuse for continuity before calling it good. You can never never NEVER call a fuse good by visual inspection....you CAN call it bad visually though!

 

[wxforecaster]

Thanks Ian. Hopefully I'll get a chance to meet you someday and offer a handshake and an ice cold beer.
Zork, I agree. Although had I not reseated all the fuses, I would have never uncovered the oxidation of the holders that subsequently failed to provide power to the PCB as well. So, in a round about way, my initial screw up did have some good with it.

First game... 209,500. Not bad

-E

 

[Pac-Fan]

Remember, Bally-Midway transformers are not guarenteed (actually any transformer) to give you exactly the stated 7 VAC and 12 VAC out of the terminals on the secondary windings.

But note, that the output is dependent on the input winding chosen, as well as your household average voltage. Midway MT-80 transformers have 4 voltage inputs on the primary: 100 V, 110 V, 117 V, 130 V. If you have 117 V at your outlet and have the input going to 117 V, you should see right around 12 V on the secondary (plus whatever delta there is inherent to the transformer design -- like too many or too few windings on that one or a cross-short between some loops causing the voltage to change). However if you have 125 V at your outlet, expect that 12V to be closer to 12.7 V.

Now, if the wires on the primary are corrected to the 110V and your power in your house is 125, thats 15 higher on input = appx 1.5 higher on output so 13.5V. You can move the primary input around to increase or decrease the secondary output accordingly.

The isolation transformer for the monitor is similar but only 3 inputs: 105/115/125 since it's got a 1:1 winding on the secondary, the delta isn't going to be that significant.

 

[thairoller]

I love this thread! I have a dead power supply and I'm about to replace the fuse holders in. Lots of great tips regarding proper voltage voltage reading. Thanks guys!