Computer Pachinko is a standard playfield for the era. Upon inserting a coin a solenoid pulls and releases the balls (typically 16) into the feeder. There are microswitches for the 8 winning pockets, but perhaps less than 8 switches since the center features often feed to the same switch too, but really you'd just need one in the back track to count a ball coming in the winning tubes, as they all congregate on the backside.
Balls that go into a winning hole get you 10 points. Balls that fall to the bottom go in to the bottom out-hole. All of the balls meet in their hopper.
If you get a certain score (operator adjustable I assume,) you could press that Replay button for a free game. It has the same effect as inserting another quarter.
It's pretty basic, but we have to remember how revolutionary an LCD display (IC! WOW!) would feel back in 1976.
For the longest time I thought Computer Pachinko was an effort to utilize the 70s machines that were being imported into North America by the ship-load, but that's not correct.
The earliest reference I've found so far was in 1976, and they were sold in the Japanese and American markets. I think they found a bit of a market for them in the NA since many more appeared here than equivalent machines of the same era in Japan.
here is a photo from a Japanese trade show, tail end of 76. Booth is operated by さとみ (Satomi), who had a brand name "Sammy" to appeal to Western audiences.
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this one was sold by ユニバーサルプレイランド (Universal Playland [UPL]) in 1977 (manufacturers would also often sell machines from other companies in that era, so probably still a Satomi-made machine)
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Pachinko was hot in Japan (the gambling kind of pachinko that pay out balls,) but the arcades there also had a long history of pachinko-style machines that would pay out prizes and tokens if got a certain score.
Computer Pachinko is one of the few that gives you a score and nothing else. No payout mech at all, but you could win a Replay.
The fact all you'd have to do to convert them is change/adjust the coin mech probably made them enticing to import, but that's pure speculation on my part. Japan runs on 100 V and most of their electronics are engineered well and still work fine on North America's voltage.
Computer Pachinkos are a GREAT addition to any gameroom, especially if you don't want to mess with traditional parlor machines and ball management. They take quarter and can normally be had for like $150 (or under) USD for a fully working and good shape one.
Here is a photo from 1976-06 Replay Magazine:
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In California they were sold by a company called Amutech:
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There were also many outfits that copied the Satomi success and took other pachinko machines and slapped them into coinop cabs for the North American audiences, especially amongst West Coast audiences like British Columbia and California.