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Sinclair ZX81 computer – Boxed, Refurbished & Upgraded to 32K RAM


Thanks for looking at our Sinclair ZX81 computer – Boxed, Refurbished and Upgraded to 32K RAM and HRG (Hi Res Graphics) Ready!
Original polys, no outer cover.

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Thanks for looking at my auction for a Sinclair ZX81 computer – Boxed (polys but no outer cover), Refurbished and Upgraded to 32K RAM and HRG (Hi Res Graphics) Ready!

We’ve performed the following work on this little beast:

  • Membrane replaced
  • Replaced the 5 volt regulator with a DC-DC converter which consumes less current and runs much cooler – it means we could also remove the huge heatsink as it’s not needed.
  • Replaced the paltry 1K memory with a 32K SRAM chip using a custom PCB – now the ZX-81 has 32K RAM internally! No more RAM pack wobble – and you get to use hires graphics (HRG) as the custom PCB also enables that.
  • All electrolytic capacitors have been changed to make sure that the ZX-81 has a stable power supply.
  • The insides of the RF modulator have been swapped out for another custom PCB that gives the ZX-81 excellent composite video output, and produces the needed back porch to allow the ZX81 to give a crystal clear picture on modern TV’s – and it uses the same socket as the RF modulator used to so that we don’t have to modify the case at all.
  • Comes with its original Sinclair ZX-81 power supply and ZX81 leaflet. The power supply has also had its electrolytic capacitors changed.

All in all, this is a well upgraded, refurbished ZX-81 with a case which is very tidy.The little man even has new rubber feet to replace the old stinky shoes he used to have!

Also, listed on eBay –

Additional information

Weight 2 kg
Dimensions 70 × 40 × 40 cm

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