Category Archives: Troubleshooting

The New Power Supply

It’s finally time for the switching power supply to take it’s place in the cabinet. Here’s the a picture of the new and old units side by side:

This may have been the most enjoyable part of the project so far. Because of Bob’s well-crafted harness it was mostly a plug & play install. The hardest part was drawing A/C power from somewhere. The transformer on the bottom of the cabinet has “utility” outlet which can be used for a light or power tools when someone is working on the machine. It seems obvious to draw power from there, but that’s not the proper way to do it. Why? Well, the “utility” outlet isn’t switched. If I used it for the new power supply, I wouldn’t be able to power the game board off unless I pulled the plug. The cabinet power switch would still control the monitor, but the game would continue running with the monitor off. Not cool! I needed a switched 120v source, so that limited my choices to the marquee backlight or the monitor. I chose the monitor because the wires were easier to get to:

Once I had A/C power running to the new power supply, it became a simple matter of mounting it in the case and plugging in the harness. I decided to put it in the same general area that the linear power supply once occupied. Here’s a shot of the cabinet now:

With everything hooked up and triple-checked, it was time to see if this would work or just start smoking.

Before I get to that, I’d like to point something out I noticed while installing the coin mechs earlier tonight:

Yep, this test session will encompass the 30,000th play! But, will Super Pacman be alive for it? I flipped the switch and was greeted with this…

Hell yeah! It’s amazing what “clean” power can do… or rather what problems “dirty” power will cause. The game booted up perfectly, played perfecly, and the muddy sound effects had also been corrected. Finally, functional Super Pacman! :D

The major repair goal I had for this machine has officially been reached. Although I would never consider it, this machine could even sit in an arcade again and earn money. It’s got all the requisite coin acceptors, locks, and playability.

Looks like it’s all cosmetic work from here on out. ;)

Ordering Parts

I figured out the list of parts I want from Bob Roberts and sent it along to him. He shot back an e-mail in less than an hour with the total price. (Thanks Bob!)

I decided on new leaf-switch style plastic for the 4 buttons. (2 Red & 2 White) This will take care of the only cosmetic problem on the control panel. I’m not ordering a replacement joystick at this point though. I plan to disassemble the original, clean each part, reassemble, and then evaluate it. I may replace the spring, but right now it looks to be in good shape. Total cost on the four buttons without leaf-switch mechanisms was $6.00. ($1.50 each)

I also ordered the replacement switching power supply for $55. I’m expecting this will solve the remaining playability issues by supplying the game PCB with clean DC power. Time will tell, but I feel pretty confident about it.

On another note, I noticed this machine is missing its coin box which sits under the coin mechs. Bob sells standard over/under coin boxes, but I was quite certain they wouldn’t fit in a Super Pacman machine. I asked Bob about purchasing a PacMan style box and he told me this:

That’s going to be a hard find. They were used in MsPac, Galaga & others, so they’ve pretty much been cleaned out of warehouses & used for the more popular games. They tell me that if you keep an eye on eBay one will pop up every once in awhile for around $10, or so.

Good advice from a true expert right there. I did a quick eBay search and I found a few Bally/Midway coin boxes, but nothing specific enough. While browsing eBay, it occurred to me that I really have no idea what the correct coin box looks like. I know a few people who own machines that use it, so I’m going to request they send me some pictures. I’m sure I’ll be able to snag one off of eBay once I know exactly what to buy.

Total cost (after shipping) on the parts from Bob was $68.50. I don’t think any of the other remaining parts will be this expensive… at least, I hope not. :)

Next plan of action…

I didn’t get much done in the way of physical labor on the machine tonight, but I did find some useful information on the web.

I learned I can replace the power supply board with an identical linear model for around $34.95 from QuarterArcade. I’m tempted, but I’ve read a lot of negative opinions regarding linear power supplies at this point. Supposedly, they will always induce some “hum” into the speaker and generally be less reliable due to the number of components and wires connecting them. They also produce more heat through the A/C to D/C conversion process than a switching power supply.

If I purchased the replacement from QuarterArcade, I would get a used model which is “tested & working”. Because even the newest “used” model is around 20 years old today, I don’t feel very confident going this route. It would probably work fine, but I don’t want to deal with this same problem again in a few years.

I also learned that Bob Roberts sells a switching power supply upgrade kit. Here’s an example picture of a Galaga PS conversion.

The Super Pacman model looks very similar. For $55, I can buy the wiring harness with a 15A switching power supply. I can also purchase the wiring harness alone, but I’m not in the mood to remove the (unused) switching power supplies from my JAMMA cabinets right now.

I struggled with this decision for a little while because I wanted the machine to remain as “stock” as possible. I concluded that the power supply is just too damn important to worry about nostalgia. A switching model will do everything the linear model does, but it will supply cleaner DC power which is generated more efficiently. Not only will this save on negligible electricity costs, but it should prolong the life of the main CPU on the game board. I plan to keep the extra linear power supply in case I ever do decide to revert back to the stock model, but I just don’t see that happening.

As an added bonus, Bob Roberts probably has the most extensive collection of “classic” parts available anywhere. He sells leaf style pushbuttons and I’m in need of those too. I’ll post the list of what I purchase as soon as it’s figured out.

It must be the power supply…

I powered on again the newly grounded machine. The vertical bars that once covered most of the screen shrank to about 1 inch across. They also changed color to black instead of a blue/black mix. This is good.

I’m now able to play a game of Super Pacman except the vertical bars get in the way. After seeing the board POST yesterday, I pretty much settled on this being a power supply issue. I disconnected the power supply PCB and began to examine it up close. I noticed this right away:

Here’s a view from the underside:

I have a few options at this point…

1. Replace the component on the board and continue troubleshooting it.

2. Take the board to ABL Electronics and let them diagnose and test it for a fee.

3. Eliminate the original linear power supply and replace it with a switching power supply.

I plan to get an estimate from ABL Electronics and read up more on swapping this board for a switching power supply. I’ve already come across a few troubleshooting web pages that insist the black bars are caused by grounding problems inherent to this type of linear power supply.

Finally got it grounded…

Admittedly, I should have done this first, but it got done nevertheless. I replaced the plug because the original plug was missing its grounding pin. These machines need to be properly grounded, so I bought a nice heavy-duty plug for it. Here’s how it looks now:

Total cost of plug: $3.99

What luck!

I replaced two of the coin door bulbs today. See the Coin Door section (under Overall Appearance) for pictures. Of course, I had to flip on the power to test the bulbs. While doing so, I noticed something interesting on the screen:

That’s right! The machine actually booted into self test mode and gave me a diagnostic on the main board amongst the scrolling vertical lines. Wow, does that save me a lot of work! I can now concentrate on the video board because the game board seems to be working correctly.

In case you’re wondering, yes. The onscreen display is upside down. No big deal. There was a cocktail table version of this game released… maybe the game PCB is in cocktail screen flipping mode. I’ll check into that later. :D

New Fuses

I had a chance to begin the troubleshooting process after work today and it went rather well. I decided to focus on the most obvious (and simple) problem scenario: blown fuses. Here’s a shot of the power supply with an arrow to the fuse block I started with.

It didn’t take me long to notice this…

The top fuse looks fine, but the bottom two are definitely blown. I looked at the other fuses and they all appeared OK. I dusted off the markings around the fuse holder and found a small listing of what fuses should be used. With used arcade machines, it’s never a wise idea to assume the in-place fuses are the correct ones so I was glad to find this. The machine calls for slow-blow fuses, rather than fast-acting. I’m guessing the monitor’s power on process causes a spike on the 12v and 5v lines and the slow-blow fuses allow for that without prematurely blowing. The daughter board of the power supply even had a time-delay fuse with a resistor inside. This thing is complicated! :)

A trip up to Radio Shack was all it took to find the necessary replacements. Total cost for the fuses: $2.39. Before I could power it on without the back door, I needed a way to secure the momentary switch. A zip-tie took care of that.

With the factory safety features successfully bypassed, I flipped on the power switch. After a short warm-up, I was greeted with the following display on the monitor:

Although you can’t tell from a single photo, the vertical lines were scrolling from right to left continuously. I was still pretty excited even though the problem appears more complicated than fuses. I’ve confirmed that the monitor works and that’s going to save me a lot of time and money in the long run.

I’ve seen similar behavior on my JAMMA cabinets with various boards I purchased on eBay. The cause typically is an under powered mainboard. I found a set of potentiometers on the power supply board that allowed me to tweak the 12v power between -0.2v and +.0.2v, so I gave that a try. After a few minor adjustments, I saw no improvement. Hmm… bad ICs, perhaps?

Well, it still could be more simple than that. Here’s a shot of the plug:

I suppose the problem could be due to inadequate grounding. I need to fix this anyway, so that will be the next troubleshooting step.