I stumbled across the VTech Precomputer 1000, learned that it's based on a z80, and looked for a schematic. I couldn't find one, so I took a crack at drawing one myself. I haven't validated it, and there are some things still to figure out, so consider it a rough starting point.
Sweet! I have some Precomputers now, and just got a Laser 50 from ebay that needs some keyboard repairs (turns out one of the keyboard matrix lines is failing). I'm going to see if I can find a schematic for the 50. It appears to be less functional than the Precomputers in terms of it's BASIC interpreter. (Strings are limited to a whopping 6 characters.) However, the Laser 50 has an important feature missing from every precomputer: A tape audio out. It's a shame that wasn't on Precomputers so that programs could be saved.
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