The ZX81 Mystery Board

Well, my post on the ultimate pimped-out ZX81 drew a lot of attention; mostly centred around the mystery expansion board that was included in the myriad of components of which this behemoth was comprised. A closer picture shows it to be some kind of EPROM from  ‘Orme Electronics’.

2013-10-13 15.04.56

But what does it do? Well, the best clues can be found from the wonderful ZX81 Stuff resource. Sadly, I can’t find any photographs to confirm but it looks to me to be the first item in their Orme list. It can’t be an EPROM programmer as the chip is soldered in and there would be no practical way of removing it if it wasn’t. Without instructions I’m still a bit lost but I’m going with an EPROM programmed with Breakout, Life and a Toolkit of some description.



Pimp My ZX81

I’ve been systematically going through The National Museum of Computing‘s collection of Sinclair equipment. It’s taken a good few months and finally I’m at the point of going through those items that, at the time, where placed in the WTF? pile. The latest candidate to come under scrutiny I have affectionally called Bluto.

Bluto 1

Pretty, huh? Yes, it’s an extremely pimped-out ZX81. I don’t have a record of the donor and have so far failed to identify the kit used to expand this humble little ‘pooter into the 80s microcomputer equivalent of an Apache gunship. Let’s have a look inside:

Bluto 2a

Wow. So, we have:

  • A keyboard which seems to be of DK’Tronics origin
  • A ZX Printer
  • The PSU
  • The mother of all cooling fans
  • An expansion board for the Z80 bus (although I have no idea how you would make use of it with the cover on)
  • A 16K RAM Pack
  • Some kind of expansion board of whose purpose I have no idea
  • Loadsa wires

Having established that nothing was going to explode upon power-up (being as sure as you can ever be with these things), I plugged it in and fiddled with the power switches. One slight annoyance with testing ZX81s is their complete silence. It’s always going to involve some mucking about to establish whether they are getting power or not (tip: multimeters help). Anyway, I tuned my old CRT tele in and got this:

Bluto 2


So, is the ZX81 itself borked or, as is often the case, some other peripheral interfering with things? Having removed the motherboard (which turned out to be a very simple job despite the hundreds of screws holding this thing together), I quickly established it was indeed in a state of borkdom. Luckily, I had a replacement board ready and waiting and so swapped them over.

Bluto 3

After a lot of cleaning, especially of the peripheral connectors, and a little gentle pushing and pulling, Bluto sprang to life once more.

Bluto 4

A real surprise was the ZX Printer, which happily sparked away onto its thermal paper.

Bluto 5

But seriously, who used such a thing? Yes you could drop it off a cliff without consequence but it looks like someone had a serious purpose for it and can’t image using Bluto for anything more than a few minutes. The fan is unbearably loud (although thankfully optional via its own switch) and the key-response time slower than an underachieving sloth. Still, maybe it go on display one day as it’s got a better chance against the regular museum key-bashing than an original membrane keyboard.

The only thing that bugs me is that expansion card. What does it do? Any ideas?



Kids at GOSH down to 2 DS Games – Can you help?


Hi all, I’ve been contacted by a friend whose sister is a nurse at Great Ormand Street Children’s Hospital. Their ward has a DS and a 3DS with a grand total of three carts, one for the DS and two for the 3DS.

Except the DS game has been lost, leaving just two to play with.

My friend was wondering if anyone out there had any old games they didn’t want anyone (or collectors with duplicates) who may like to donate them to some kids who may well to be spending Christmas in hospital this year. Maybe a round or two of Mario Cart will take their mind off their problems for a bit.

To ensure any donations are handled correctly, I’ve been ask to post a link to the official page for donations (attached below). The ward in question is ‘Dinosaur Ward’.

So, I’m off to have a dig through some old games. If you could do the same I’m sure you’ll be bringing a smile to somebody’s face.

If you could take the time to share this with anyone you think may be able to help, that would be brilliant.

All the best,



Image from