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

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!