March 2, 2024

Benjamin Better

Better Get Computer

Computer Space Flies Again | Hackaday

Computer Space Flies Again | Hackaday

[Sean] from Common Arcade Repairs fixes traditional arcade equipment, and he received a ask for to repair a incredibly distinctive device. It is Laptop Place, the very first commercial arcade cabinet ever manufactured, and loosely based mostly on Spacewar! This grand-daddy of coin-op was a literal barn come across, and was in fairly negative form soon after sitting down for years. All the components appeared to be primary, building them 50 years aged. As you can consider, that mixture didn’t bode effectively for the wellbeing of the components. There’s a couple hours of footage listed here, but it’s priceless troubleshooting assistance, and really neat to see this kind of an outdated device getting labored on.

Component a person is the intro, and [Sean] started out with an HP logic analyzer, just probing the lots of TTL chips on the board looking for floating or if not suspicious outputs. Determine out the definitely defective chips and swap every single with a socket and new chip. Just about every diode in the device required changing.

Portion two of the maintenance begins with a broken trace maintenance, and the discovery that all the ceramic capacitors on the boards were being leaky. The fascinating matter is that a multimeter tested these caps as obtaining the proper capacitance, but a devoted leak tester learned the dilemma.

Component 3 demonstrates the method of operating the remaining chips as a result of a logic tester, which located much more problematic ICs. In some cases, a chip would only from time to time check as operating. And strangely, one of the new, alternative chips turned out to have a trouble. While as a commenter pointed out, it could be a falling edge vs climbing edge variation of the logic chips to blame. Or it’s possible the new chips were being counterfeit. Challenging to nail down.

Portion 4 begins with a gotcha instant, wherever a single of the to start with repairs to the board was a misstep. What appeared to be a weakened trace, was actually a manufacturing unit modification (a bodge cut?). Then a fortunate split genuinely assisted out, wherever only fifty percent of a person of the 7476 chips was in use, and one particular of the chips on hand was only half doing the job. Put the useless bit into the unused slot, and the machine actually started off to behave.

Element 5 is the victory lap, exactly where all the parts last but not least arrived, and anything begins functioning on the bench. How great to see the old device bleeping and blooping all over again.