Икар 64 (Icarus 64): Part 3

This is a well-built “tank“ of a ZX Spectrum clone .. or “household computer“ (бытовой компьютер) ... running on a genuine Z80 that was first built in the Ukrainian SSR, and then independent Ukraine (1991-1993) ... as far as I can tell. I managed to fix my original machine (ROMs installed incorrectly, dodgy ROM socket), however when replacing the ROM sockets a stray piece of metal managed to get under one of the logic chips (I think), so the machine then stopped working. Finally managed to get a hold of a second machine. This one is working but has poor RGB output. There is obvious difference around the RGB circuitry in both machines, with the 2nd “dodgy RGB“ having some cut traces and bodge wire installed. The two chips related to the bodge work are a КР1533ЛП5 (74LS86, quad 2-input XOR gate) and an interesting К155РЕ3 (S8223, 256bit (32x8) PROM) which is labelled “44“. This chip is obviously not easily replaceable unless its contents are dumped. I don’t have any schematics for the machine, so I’ll try to draw up the RGB output circuit so I can understand (pfft, okay) what the bodge wiring is for ... maybe I should revert it back to what the original machine has as I’m pretty sure this had a stable RGB output ... ? ROMs can be found here if interested: Other videos on the Icarus 64: