Improved Wiring

I finished up my custom Super-Pac-Man-cabinet-to-JAMMA wiring harness tonight. I removed all of the unused wires from the JAMMA harness, bundled the necessary wires into wire loom, and sealed the exposed solder connections in hot glue. This really help to unclutter the cabinet and I’m quite happy with how it came out.

Here’s how a connector looks with hot glue sealing it up:

Nothing a little hot glue won't solve...  :)

In addition to protecting the connector from shorting out on exposed metal parts in the cabinet, it also prevents strain on the solder connection. Bob Roberts’ switching power supply harness used this technique and I basically imitated it. If you’re really observant, you might have noticed I switched to a different style of pin header as well. I found a longer strip that could be custom-sized to the exact length I needed instead of using three of them in a row. Using three pin headers in a row would have made the hot glue application much more difficult.

I’m sure I could clean the wiring up a little more, but overall I’m satisfied with it. Here’s how it looks now:

Improved wiring...

Coin Door $0.25 Labels

The coin door had two little squares inserts to indicate the cost of a game is $0.25. All Midway coin doors from the USA seem to have these. I believe the originals are made of Lexan and the label itself is silk screened on the reverse side.

One of the originals was in fine shape but the other had some sort of adhesive on it. Here’s a picture:

Adhesive on the insert label.

I went to great lengths to clean it off without damaging the original. I researched adhesive removers that were known to be safe on polycarbonates, bought a few of them, bought a small sheet of Lexan to verify it wouldn’t cause damage and went to work. Unfortunately, I had no luck dissolving the adhesive. I actually had a product sitting around from another project called Novus Plastic Polish and the next step would have been polishing off the adhesive. Novus Plastic Polish is touted for use on motorcycle windshields, so it probably would have achieved a reasonably clear, scratch-free finish. However, around the same time, I stumbled across the only place that sells reproductions and decided I’d rather pony up $5 on a new set at this point.

They’re not 100% perfect reproductions, but they’re pretty darn good. Here’s how they look installed:

Reproduction insert.

Reproduction inserts.

Intermittent Red Problem Resolved

As I mentioned before, I had an issue where the red color would disappear from the screen. When I installed the cap kit, I looked closely for lifted solder pads. I focused on the pin header where the main PCB connects to the monitor chassis because I found I could provoke the problem by putting a little pressure on the connector. Unfortunately, I didn’t see anything that looked wrong with it. Once everything was reassembled, reds were present on the screen and I figured I had it fixed. Well, playing the game for a short while the following day proved me wrong. I still had an intermittent connection on the red signal.

After testing the monitor cable extensively to rule it out, it was time to pull the monitor chassis out again and inspect it. I figured I would just re-solder all of the pins on the main signal connector, but I really wanted to see if I could spot the problem first. It was tricky to see in bright light–probably due to glare from the shiny solder–but I managed to get a picture of it. This was the culprit:

The reason why red colors occasionally disappeared from the screen.

I probably could have reflowed the existing solder, but instead I used desoldering braid to remove it and then applied new solder. After putting it back together, I tested it out and I’m happy to report the problem is finally resolved. :)

Coin Chutes: Before & After

I continued reassembling the coin door and noticed the coin chutes were a bit rusty and dirty. I figured I should clean them too. The under side of the chute was fine, so I just removed the outer cover. I then used a Dremel wire brush attachment to knock off the minor surface rust and then some Mothers Mag & Aluminum Polish to shine them up. Here’s what a clean one looks like next to a non-cleaned one:

One side down, one to go...

…and here’s how they ended up:

Much better!

When the covers were off, the inside of the chutes were exposed so I also cleaned them with the Dremel wire brush. There are also two small rectangular plastic inserts that sit inside the chute and mate up with the outer plastic piece of the door. I cleaned those by removing them and dropping them in a small cup of Simple Green. The inner side of the plastic rectangle is just slightly wider and taller than a quarter so this seemed like the best way to clean it. It worked pretty well because the green cleaning solution had turned nearly black when I checked on it a couple hours later.

Now, I just have to do something about the coin counter.

Multi Game PCB

I ordered a Programmable Multi Game JAMMA PCB from ArcadeShop.com and I found JammaBoards.com had a full JAMMA wiring harness for only $10. I noticed they also sell a selection of multi-game PCBs for far less cost than the ArcadeShop multi-game PCB. I was back and fourth deciding which multi-game PCB to buy and finally decided to go with the more expensive ArcadeShop board because it generally gets better reviews in the forums, is more customizable, and has a prettier menu system. I’ve decided not to include the cost of this PCB in the Total Cost section because it’s not really necessary to the project and the cost of the ArcadeShop multi-game PCB alone exceeds the entire cost of the project. (and that sort of depresses me)

I did have a good time assembling a custom Super Pac-Man cabinet to JAMMA harness. It really wasn’t too difficult because the pinouts for JAMMA are an established standard and the pinouts for Super Pac-Man are easily available as well. I bought some connectors to fit the cabinet wiring and soldered the leads from the JAMMA harness to the correct pins in the connectors. Here’s what they look like:

Sound and control harnesses.

Video harness.

Note the arrow on the video harness. It’s pointing to two pins for the negative horizontal and vertical sync signals. I found out these two must be bridged to give the Electrohome G07 monitor the signal it needs to sync the picture when getting output from a JAMMA-connected PCB. Without bridging these two pins, the picture was nearly impossible to stop from rolling on the screen. I really don’t understand monitor circuitry well enough to explain why this is. Here’s some corroborating evidence that helped me out. Also, a big thanks to the monitor experts on the BYOAC forum for helping me spot this subtle detail. I will eventually seal the ends of the connectors to prevent any short circuits, but I was impatient and wanted to try it out.

With the harness assembled, I just had to put it all in the cabinet. The right side of the machine was bare from the factory, so it looked like a perfectly good place to relocate the power supply and install the multi-game PCB. I also reinstalled the old linear power supply, but it’s not hooked up to anything. It’s just there because I have no other good place to store it. Here’s how it looks:

Multi-game installed.

I know, I know… I need to clean up all the wiring I added, but it does work for now. I’ll post some photos or video of the screen soon. It’s pretty slick.

Monitor Chassis Work

The monitor in this cabinet is an Electrohome G07 built in 1982, so it’s about 28 years old today. This model was very common in Bally/Midway machines from the early 1980s and fortunately there is a lot of great information and troubleshooting advice available. The monitor still worked fine, but I decided the time had come to perform some preventative maintenance. Specifically, cleaning the chassis, installing a cap kit and replacing the flyback transformer.

A cap kit is essentially a bundle of new capacitors that match the existing capacitors on the chassis. When an electrolytic capacitor ages for nearly 30 years, it tends to wear out and no longer functions at the same specs it was built for. This stresses other components on the chassis and, if left long enough, will eventually cause more expensive (and hard-to-find) components to fail. Of course, it can cause odd issues with the picture too. Cap kits are fairly inexpensive and readily available from Bob Roberts. I bought the “deluxe” repair kit because it included a new flyback transformer and some other odd parts I may need in the future.

I began by discharging and removing the monitor chassis. I won’t go into details because other people have already done a fine job of it. I will include the obligatory warning that working on any CRT is dangerous due to high voltages that may be present. These high voltages may be present even if it the CRT has been unplugged for a long period of time. So, if you don’t know what you’re doing, I don’t advise tackling this sort of work.

Once I got the chassis out, here’s what I had in front of me…

The main chassis with 28 years of dust.

The neckboard with 28 years of dust.

The smaller board is called the “neckboard” as it plugs into the neck of the CRT. Both were quite dirty. These parts are in a magnetic field when the monitor is running and they seem to attract dust like, umm… a magnet. I’ve read a lot of methods on how to clean one of these boards without doing harm to it. Some people go over them with q-tips while others hose them down in a sink and then dry in an oven on low heat. I’m sure either of those extremes is fine, but I didn’t want to waste time with q-tips and I didn’t want to involve an oven. I opted to rinse it down with a lot of rubbing alcohol because it’s generally safe on electronics, dries quickly, and won’t leave mineral deposits behind. I also used a cheap paintbrush and Simple Green in places where the the alcohol wasn’t loosening enough dirt. It was much cleaner and completely dry within an hour or so.

It was then time to install the cap kit and flyback transformer. A while ago I noticed I had a minor issue with the red color on the screen disappearing occasionally. While installing the cap kit, I looked very hard for any lifted solder pads on the chassis. I also did quite a bit of testing with my multimeter. I only found one spot that was definitely causing an intermittent connection and it happened to be one leg of a capacitor I had to replace. While I was at it, I performed the C303 upgrade on the chassis to help with “curling” problems. Details on the upgrade are available here.

Here’s how it looked after all the work…

The main chassis with 28 years of dust.

The neckboard with 28 years of dust.

I finally put the chassis back in the cabinet and it powered it up. No sparks, exploding caps, or fire—just a nice clean picture and consistent red colors on the screen. Exactly what I was hoping for. :)

Update On The Game Board

It’s been quite a while since I wrote about the main game board. My last posting mentioned that I was going to install a code upgrade and a non-volatile SRAM chip to make this machine preserve high-scores after being powered off. I did actually complete this upgrade about 5 years ago and didn’t post anything about it. It was a lot fun too! I bought a EPROM programmer from eBay for about $50 and figured out how to use it. Then, I bought the two chips I needed, programmed, and finally installed them into the sockets on the game board. I remember the first power-up with the new chips resulted in a garbled display. I powered it off and was about to pull the new chips to test them. For whatever reason, I decided to power it on again and to my surprise it worked perfectly from there on. I guess the first power-up was some sort of initialization of the memory chip or something. Anyway, high scores are now able to be saved and I’ve been quite happy about it. I recall the SRAM chip has roughly a 10-year lifespan which is pretty decent considering how small it is. I don’t recall the data size it can hold, but I believe it was 12KB. (probably 11.9KB larger than it needed to be)

Why bring this up now? Well, partly to trumpet the progress I made but also to mention my recent change in direction with this cabinet. Since I fixed the original power supply issue and returned it to playability, my goal has been keeping the cabinet as close to original as possible while fixing up any cosmetic issues. That’s still the goal, but I recently decided it’s OK to expand upon the usefulness of the 4-way leaf-switched joystick and vertically-oriented monitor by adding some new games to the cabinet—as long as it is done cleanly, tastefully and is able to be completely reversed with minimal effort.

I already own a few dedicated MAME cabinets and I’m not aiming to turn this into another one. In fact, I’m not even going to mess with the original wiring in the cabinet. The only thing I’m going to add is a selectable game menu upon start-up. It will be along the same lines as what Jeff Hanson did with his Super Pac-Man. The only games will be a small selection of classics that were built for this sort of cabinet. (i.e. Pac-Man, Ms. Pac-Man, Super Pac-Man, Galaga, Donkey Kong, Dig Dug, etc.)

How is this possible without fully MAME‘ing the cabinet? Simple—I’ll build a custom JAMMA harness to interface with the original cabinet connectors and add a Programmable Multi-Game JAMMA PCB. I’ll be able to unplug the original game board and plug the new board in using the exact same connectors. Very clean and very easy to reverse. More details on what this will look like are on their way…

Retr0Bright

With all of the parts removed from the coin door, I thought it would be wise to give them a thorough cleaning before reassembly. The coin acceptors on this machine are gray plastic and looked somewhat brown-ish. Because hands touch this area when inserting a coin, I figured it was simply accumulated grime I could scrub off. Scrubbing them in soapy water did remove some of it, but there was still a distinctive brown hue left on the plastic. This reminded me of something I read about recently…

If you’ve ever seen beige or gray plastic age over a number of years, it does sometimes develop a brownish hue. Some chemistry geniuses at the English Amiga Board figured out this is caused by a breakdown of atomic bonds in the plastic. Bromine is added to plastic during the manufacturing process to act as a flame retardant and it eventually finds its way to the surface. UV light tends to accelerate the process. I’m no chemist, so that’s the best explanation I can provide. You can read the real theory behind it here. I found it fascinating.

The same geniuses who figured out what was causing this problem also figured out how to reverse the process without damaging the part. Simply coat the part in a solution they developed and expose it to UV light for a number of hours. I’d never tried it before, but I’ve been curious to see how well it would work. The solution itself is easy to make and the developers have given out the recipe for free on their wiki.

I mixed up a small cup of the solution and dropped in one of the coin acceptors. I then put it under a black light to provide some UV exposure per the instructions. Here are the treated and untreated coin acceptors side-by-side after 12 hours: (I adjusted the contrast and brightness to make the difference stand out more)

Front side

Back side

So, Retr0Bright does work. Awesome. :)

Door Plate

The coin doors on Midway/Bally machines of this era have a front-facing metal plate with the company logo. The majority I have seen are pretty scratched and dented. This one wasn’t too bad, but because I needed to strip the door to powder coat it, I had to remove it. I found that ArcadeShop.com sells a reproduction for $15, so I picked one up. Here’s how it looks next to the old one:

Old & new.

And, of course, I had to put it in place to see how it would look on the door. :)

On the door.