[Sean] from Classic Arcade Repairs fixes classic arcade machines, and he got a request to repair a very special machine. It’s Computer Space, the first commercial arcade cabinet ever made, and loosely based on Spacewar! This grand-daddy of coin-op was a literal barn find, and was in pretty bad shape after sitting for years. All the parts appeared to be original, making them 50 years old. As you can imagine, that combination didn’t bode well for the health of the components. There’s a couple hours of footage here, but it’s invaluable troubleshooting advice, and very cool to see such an old machine being worked on.
Part one is the intro, and [Sean] started with an HP logic analyzer, just probing the many TTL chips on the board looking for floating or otherwise suspicious outputs. Figure out the obviously faulty chips and replace each with a socket and new chip. Just about every diode in the machine needed replacing.
Part two of the repair starts with a broken trace repair, and the discovery that all the ceramic capacitors on the boards were leaky. The interesting thing is that a multimeter tested those caps as having the correct capacitance, but a dedicated leak tester discovered the problem.
Part 3 shows the process of running the remaining chips through a logic tester, which found more problematic ICs. In some cases, a chip would only sometimes test as working. And strangely, one of the new, replacement chips turned out to have a problem. Though as a commenter pointed out, it could be a falling edge vs rising edge variation of the logic chips to blame. Or maybe the new chips were counterfeit. Hard to nail down.
Part 4 starts with a gotcha moment, where one of the first repairs to the board was a misstep. What appeared to be a damaged trace, was actually a factory modification (a bodge cut?). Then a lucky break really helped out, where only half of one of the 7476 chips was in use, and one of the chips on hand was only half working. Put the dead bit into the unused slot, and the machine really started to behave.
Part 5 is the victory lap, where all the components finally arrived, and everything starts working on the bench. How cool to see the old machine bleeping and blooping again.
Nice work!
Though that’s not Spacewar but Asteroids without the asteroids, just UFO opponents.
Spacewar was a two-player game only, in which one of the two ships looked like a top view of the Star Trek Enterprise and the other was the same chevron used in Asteroids. Computer Space is a one-player version of Spacewar where the machine plays the other opponent.
I have played original Space War! on a genuine restored PDP1 at the computer history museum in California from Europe. The presentation demonstrated some other things as well and told of its restoration. The presentation was given by two good ol’ boys who were part of the original coders who wrote Space War! in the first place!! as well as made some of the other things they demonstrated and were part of the restoration/ preservation effort. Well worth a visit if your near by.
I think they have one of these at Funspot in laconia,NH. I bet the maintenance guys there would have some interesting things to post if someone could get them to contribute here..
What, no mention of the game’s appearance in the classic movie Soylent Green?!? :-)
This reminds me, I really must fix my Battlezone. First challenge is to fund the bloody security key to open it!!!
try: GoFindMe
or just look into the lock picking lawyer videos
I want a cabinet like that for my home automation command center.
I first saw this machine on the boardwalk at the Jersey Shore when I was about 10 yrs old (I’m 60 now). Was totally intimidated by it.
Ah yes… the old circuit board with all the chip numbers sanded off trick.
That was always… special… when you had to work on one of those