Tuesday, August 17, 2004

King of the Soldering Iron

About a year ago, we finished our basement to create a home theatre. One of the nice features of our new space is the addition of a couple of arcade games. We have a Theatre of Magic Pinball machine and an old classic PacMan machine.

Little did I know what I was getting into with these machines. I'll start with PacMan.

The screen went dead. The game would play, I know this because I could hear it through the speaker, but the screen was completely dark. I tried picking up another monitor on eBay and installing it, but had the same problem. So I gave in and called a local arcade repair specialist who came out to look at it. Turns out both monitors had blown capacitors. He installed a "cap kit" and it was good as new. A couple of weeks later, I was playing the game when my son accidentally kicked a Nerf ball that hit the cord where it plugged into the wall. The game went completely dead. No lights, no nothing.

I figured it was a blown fuse, so I replaced all the fuses I could see. No luck. I tinkered around with it for a while, and a friend finally lifted a piece of paper to reveal two more fuses that I hadn't seen. $2.00 later, we were back in business. The problem then was a "hum bar." That is where the screen has a wave that floats across it, right to left. It also hums loudly through the speaker. I did some internet research and learned that the wiring harness used to plug into the main board is typically weak and usually fails after a few years. I bought a new plug, and rewired all 52 (or so) wires into the new plug. I plugged everything back in, and we now have a beautiful, perfectly played PacMan machine. Except now, the machine resets every so often (20 minutes or so). So high scores disappear (it can't remember anything after a reboot). Jeez.... what next???

The pinball machine has been a little more steady. The first issue had to do with it becoming confused about how many balls were in play. It would keep kicking balls into the shooting lane even during play. This was simply a loose connector below the playfield. The next problem came when one flipper quit working. In this case, a wire had come loose, so a little solder made it all better.

The biggie was when the lights in the back box (the big display above the playfield) when out. A fuse, I figured - no big deal. I opened up the case to find a white molex plug completely burned through. Wow, black and cripsy. I've since discovered that this is pretty common on Williams/Bally pinballs of that era. The manufacturer didn't use heavy enough pins and wires to run all those light bulbs. Leaving the machine on 24/7 at full brightness will cause this plug to burn out after a while.

I rebuilt the plug, and fired it up to find only half of the lights working. After doing some continuity tests using my multi-meter, I determined that the back of the circuit board had broken contact when the plug burned up. I unplugged the board and pulled it out, and sure enough, the solder on that pin had gotten so hot, it melted and lost contact.

I've never done any kind of soldering on a board before, so I was quite nervous. I've only soldered wires to make connections, and usually I do a pretty poor job of that. I dabbled just a small amount of solder on the back side of the board to restore the connection to the pin. I then tested it with my multi-meter and all looked good. I plugged the board back into the machine and fired it up. YES! All lights are burning brightly!!!

Now, how to avoid that burning problem again... These pinball machines have an extensive menu for controlling all aspects of the machine. I set it to "dim" after 2 minutes of idle time, and I set the "dim" setting to its dimmest. So now, after 2 minutes, the lights all dim which will hopefully pass less current through that plug, preventing the burning problem. I could also replace all of those bulbs will a similar bulb that burns less brightly. At any rate, I was very proud of my soldering skills to fix that bad connection.

Now, back to that PacMan reset problem........

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