RAM: 1KB (internal), 16KB (expansion, replacing the internal 1KB)
Composite Mod
Trivia
The ZX81 was my very first computer. Unfortunately I damaged my original device in a modification attempt back in the mid-1980s, and disposed it after that. This ZX81 looks very similar to the one I had, so I bought it as a memento.
It came with a 16KB RAM expansion, but that one turned out to be irreparably broken.
Restauration Works
Restauration was carried out in December 2021
Case cleaned
Modified the modulator to create a composite signal, reversible
All electrolytic capacitors replaced with new, long-live types
Replaced 7805 with Traco Power TSR-1 DC/DC converter, and removed heatsink
ULA and CPU heatsinked
Keyboard membrane connector broke off during restauration due to old age, but could be recovered
Known Issues
Missing rubber feet
History
2022-01-08: Recapped new RAM expansion
2022-01-02: Bought another ZX81 16K RAM expansion
2021-12-26
Composite mod (by a transistor inside the modulator)
Replaced 7805 with TSR-1 DC/DC converter, removed heatsink
Glued heatsinks on ULA and CPUs
Accompanying RAM expansion is irrepairable broken (custom ULA chip) and is stored
