Sinclair ZX80 / ZX81 / Z88 Forums

Check the power supply to see if the input filter caps have gone. I had a similar problem with my HP logic analyzer. The Rifa branded caps on the mains input had exploded. Normally not terminal, but they will need replacing as if they have gone they will be shorting out the input. HTH Regards Andy

Wifey has banned me from buying any more computer kit

He gave many a young lad, including this one, the ability to learn computing. In what was (at the time) an extortionatly expensive hobby.

RIP Sir 'Uncle' Clive, you legacy still lives on and will do so for many years to come

Nice one. I might give that a go.

Really interesting project. Can't wait to see the finished version.

Just add a 10 ohm resistor to position R30. All you need to know found in this thread with excellent information provided by 1024MAK.. https://www.sinclairzxworld.com/viewtopic.php?f=7&t=2209&p=22712&hilit=R30#p22712 Also the ebay item requires a composite input not the UHF output provided by the Z...

Something like this might do the trick. It would mean not having to go inside the ZX81 and doing any surgery. https://www.ebay.co.uk/itm/PAL-NTSC-Bi-direction-Mini-Converter-PAL-NTSC-Converter-PAL-to-NTSC-TV-Format-/224288353710?_trksid=p2349624.m46890.l49292 Not having to have ever used one I dont ...

Nothing that I've got of that vintage, Sinclair, Commodore or Acorm seems to have any issues cap wise. Unless someone has inadvertently damaged them physically. It seems to be something that occurs from eary to mid 90's stuff. When things changed to SMD aluminium electrolytic. This is one of the thi...

Agreed. Unless the capacitors are physically bulging or are leaking electrolyte you can leave them alone. You generally find that there are computers that do need recapping as a matter of course such as some Apple Mac's and Commodore Amiga 600 and 1200's to name a few, but these are normally down to...

Thank for the link.

Spent a couple of hour's this afternoon laying out the CPU/ROM/RAM part of the circuit in Circuit Studio.
It's amazing how much more you learn about about these old computers when your laying out a circuit from scratch.

Kind regards
Andy