Space invaders repair
| Project Space invaders repair | |
|---|---|
| |
| My attempts in repairing a Space Invaders Console from 1977 | |
| Status | In progress |
| Contact | Mahjongg |
| Last Update | 2017-04-02 |
I was asked if I could repair a defective space invaders console by my friends at Awsomespace, and I said yes. This describes the vicissitudes I experienced while attempting this feat.
Note this isn't actually a RevSpace project, (as all the work is none at the Awesomespace location in Utrecht) but I still thought it was note worthy to document my experiences somewhere, as actual information is hard to come by.
The symptoms of the problem were that the console when turned on only displayed a screen full of "garbage", that is, a screen filled with a repeating pattern of seeming random pixels repeating something like eight times over the screen, with no discernible motion in this pixels.
The console had been found standing in a few inch of water in a cellar somewhere, so we feared the worst for the condition of the electronics, luckily our fears were not met by reality, as the electronics looked fine, only the very large mains transformer on the bottom of the console had been a bit wet and the woodwork has suffered.
The console came with an original document "Midway's SPACE INVADERS PARTS CATALOG" dated October 1978, "game no 739", and heavily yellowed hand drawn schematic of the main (CPU) board, and a secondary sound and I/O board. My first task was to create electronic copies from them.
after quickly verifying all the relative power supply voltages were okay, (they were) I realised that to debug these boards I had to get them on a workbench, power them independently from the consoles power supply, which wasn't really portable in any sense, so I started creating a suitable power supply from an old PC power supply. I also started looking at further documentation and soon found out that any kind of detailed description about how it all worked internally wan't available at all, and looking at the schematics I soon found out that it was an Intel i8080 based system and was really designed very strangely, which isn't surprising as it really was the very first design incorporating a microprocessor, and video logic. It looked like something an alien being had designed, and went against all modern design concepts of an 8-bit computer system, the only thing it somewhat resembles was an old S100 bus based system, as it didn't have a bidirectional databus, but two unidirectional ones. and also incorporated what looked like data-line multiplexers.
I discovered some valuable documents, the main being the official repair manual,