A Feast Of 1970s Gaming History, And An 8080 Arcade Board

Sometimes a write-up of a piece of retrocomputing hardware goes way beyond the hardware itself and into the industry that spawned it, and thus it is with [OldVCR]’s resurrection of a Blasto arcade board from 1978. It charts the history of Gremlin Industries, a largely forgotten American pioneer in the world of arcade games, and though it’s a long read it’s well worth it.

The board itself uses an Intel 8080, and is fairly typical of microcomputer systems from the late 1970s. Wiring it up requires a bit of detective work, particularly around triggering the 8080’s reset, but eventually it’s up and playing with a pair of Atari joysticks. The 8080 is a CPU we rarely see here.

The history of the company is fascinating, well researched, and entertaining. What started as an electronics business moved into wall games, early coin-op electronic games, and thence into the arcade segment with an 8080 based system that’s the precursor of the one here. They even released a rather impressive computer system based on the same hardware, but since it was built into a full-sized desk it didn’t sell well. For those of us new to Gremlin Industries the surprise comes at the end, they were bought by Sega and became that company’s American operation. In that sense they never went away, as their successor is very much still with us. Meanwhile if you have an interest in the 8080, we have been there for you.

Solving The Mysteries Of Grounding While Improving A Power Supply

Grounding problems and unwanted noise in electrical systems can often lead to insanity. It can seem like there’s no method to the madness when an electrical “gremlin” caused by one of these things pops its head out. When looking more closely, however, these issues have a way of becoming more obvious. In a recent video, [Fesz Electronics] shows us how to investigate some of these problems by looking at a small desktop power supply, modelling it in LTSpice, and reducing the noise on the power supply’s output.

While everything in this setup is properly grounded, including the power supply and oscilloscope, the way the grounding systems interact can contribute to the high amount of noise. This was discovered by isolating the power supply from earth ground using electrical tape (not recommended as a long-term solution) and seeing that the noise was reduced. However, the ripple increased substantially, so a more permanent fix was needed. For that, the power supply was modelled in LTSpice. This is where a key discovery was made: since all the parts of the power supply aren’t ideal, noise can be introduced from the actual real-life electrical behavior of some of the parts. In this case, it was non-ideal capacitance in the transformer.

According to the model, this power supply could be improved by adding a larger capacitor across the output leads, and also by increasing their inductance. A large capacitor was soldered in the power supply and an iron ferrule was added, which decreased the noise level from 100 mV to around 20. Still not perfect, but a much needed improvement to the simple power supply. If, on the other hand, you want to make sure you eliminate that transformer’s capacitance completely, you can always go with a transformerless power supply. That carries other risks, though.

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