[Sean] from Vintage Arcade Upkeep fixes vintage arcade machines, and he were given a request to fix an overly particular system. It’s Pc House, the primary business arcade cupboard ever made, and loosely in keeping with Spacewar! This grand-daddy of coin-op used to be a literal barn in finding, and used to be in beautiful dangerous form after sitting for years. The entire portions gave the impression to be unique, making them 50 years outdated. As you’ll be able to believe, that aggregate didn’t bode neatly for the well being of the parts. There’s a pair hours of pictures right here, however it’s beneficial troubleshooting recommendation, and really cool to peer such an outdated system being labored on.
Section one is the intro, and [Sean] began with an HP common sense analyzer, simply probing the various TTL chips at the board on the lookout for floating or in a different way suspicious outputs. Work out the clearly inaccurate chips and exchange every with a socket and new chip. Almost about each diode within the system wanted changing.
Section two of the restore begins with a damaged hint restore, and the invention that the entire ceramic capacitors at the forums have been leaky. The fascinating factor is {that a} multimeter examined the ones caps as having the proper capacitance, however a devoted leak tester found out the issue.
Section 3 displays the method of working the remainder chips via a common sense tester, which discovered extra problematic ICs. In some circumstances, a chip would best from time to time check as running. And unusually, probably the most new, alternative chips grew to become out to have an issue. Despite the fact that as a commenter identified, it can be a falling edge vs emerging edge variation of the common sense chips in charge. Or possibly the brand new chips have been counterfeit. Onerous to nail down.
Section 4 begins with a gotcha second, the place probably the most first upkeep to the board used to be a misstep. What gave the impression to be a broken hint, used to be in reality a manufacturing unit amendment (a bodge lower?). Then a fortunate damage in reality helped out, the place best part of probably the most 7476 chips used to be in use, and probably the most chips readily available used to be best part running. Put the lifeless bit into the unused slot, and the system in reality began to act.
Section 5 is the victory lap, the place the entire parts after all arrived, and the whole lot begins running at the bench. How cool to peer the outdated system bleeping and blooping once more.