Electronics/Wiring
As I said, this game had a lot of issues that needed to be addressed.
- The MPU would not boot.
- The Power Board had been "MacGyvered" so that the bridge rectifiers had been moved off the board and installed on their own metal base. Also, connector J2 had been hard-wired to an old EM style connector. While unconventional, these worked and were a good workaround. No need to “fix” this immediately since it was working.
- The previous owner must not have had a connector for the driver board J3 connection (25 pin .100 top right). So, he directly soldered wires to the driver board pins and then soldered the other end of the wires to a Gottlieb style edge connector he had "sawed off" from some circuit board. He then screwed this into the cabinet head next to the Driver Board J3 connector. He then put the incoming wires into a Gottlieb style connector housing. This allowed him to connect and disconnect this connector without having to remove the driver board. It was an odd way to fix the problem. My assumption is that he didn’t have any of the .100 connector housings and made do with what he had. Note the picture of this in the right pane.
- Sound worked initially, but after sitting unused for several years, the sound did not work when I got the game running again.
Fixing The MPU
To get the MPU to boot, I installed new ROMs. I used a known good MPU and could not get the first flash on the test boot sequence. So, I knew it was probably the game ROMs. After installing a new set of ROMs, the board booted all the way! So, I was able to play the game for a year or two before I started cannibalizing displays and the driver board. Once I came back to restoring the game, the MPU would not boot all the way. It failed after the second flash suggesting that the U8 5101 RAM was bad. As a result, I decided to install an Alltek MPU. I figured my old board was almost 45 years old so the new replacement was a better choice.
Fixing The Rectifier Board
Next, I needed to address all of the jerry rigging that went into the Rectifier (power) board. I appreciate the work the person did in keeping the game going, but it left me with a lot of work. There were three things they did to the board. (See picture at right)
- They had directly soldered wires to the 20-pin J1 pins. Thus, you could not disconnect those wires at the board!
- They moved the bridge rectifiers off of the main board onto a separate metal base. They then jumpered wires from there to the board.
- They directly soldered wires to the J2 connector pins. They then ran these wires to an old EM style connector that they screwed into the cabinet “above” the rectifier board. They then used an EM style connector to connect those wires. Again, a fix that worked and allowed them to disconnect J2, but would cause a lot of work for me later to address.
I decided that the rectifier board itself was too far gone to be salvageable. I bought a new replacement X-Pin board and installed it. If you follow their instructions, these are easy to install as there is no soldering required. The biggest headache was that every connector housing had to be redone. I was doing all of the connectors anyway, but the condition of the wires and and the fact that some of them had been spliced so that the wire colors didn't always match the schematics. So I had to take my time making sure I had the correct wires. Also, where there was a splice with a wrong wire color, I replaced it with a wire of the correct color. Then, making sure that I had the correct wires when disconnecting from the makeshift EM connector meant constantly looking at the schematics and verifying all of the wires. Note that I re-did every connector in the game that connected to any board, so I guess I shouldn't complain. It probably didn't cost me as much time as I'm complaining about.
One caveat to remember is that the X-Pin board can be used in the older Bally rectifier boards as well as the one used in Space Invaders. The difference is that number of pins for the J2 connector (9 versus 8) is different. Make sure you get this correct. The instructions tell you how to handle this.
Fixing The Driver Board Jerry Rigging
As I mentioned, the game had a wild workaround for the J3 connector (see pic at right). Basically, I just removed their “contraption,” clipped all the wires, and then installed the correct 25 pin, .100 connector. Since I was doing all the connectors anyway, this wasn't a big deal.
Fixing The Sound Board
The sound board worked originally. After sitting for several years, it did not work. To be honest, the sound boards are a bit of a “black box” and there is little repair information on them. I knew my speakers were good as I was getting a hum or some “noise” at times. After checking my wiring and connectors again, I decided to buy an after market replacement board made by barakandl.
