All of my nice ZX81s are carefully packed away in boxes. Somewhere.
Unable to find those, in the last few posts, I have been repairing what I was able to find, a selection of broken ZX81 boards.
This was the case I found with them.
Not very good, is it?
I think I had bought that and the boards as a bundle at some point about 10 years ago. Probably with the intention that the case would be a good candidate to sand down and spray white to make one of the ZX80 style ZX81 case mods for a Minstrel 2 board that I used to do many years ago, at a time when there were plenty of unwanted and unloved ZX81s on ebay for next to nothing.
I have now repaired two of the three boards, one is now a bench test board, and the other is ready to go back into the ZX81 case, complete with ROM and RAM upgrades, a switching regulator, a composite mod and a heatsink on the ULA.
- https://blog.tynemouthsoftware.co.uk/2026/09/zx81-repairs-board-1.html
- https://blog.tynemouthsoftware.co.uk/2026/09/zx81-repairs-and-upgrades-board-2.html
Membrane
For some reason, the keyboard membrane had been covered in Sellotape (other brands of clear adhesive tape are available).
As it write this up, it occurs to be that someone had possibly been trying to do a new paint job, trying to prepare the top and masking off the keyboard with the tape?
The tape peeled off OK, leaving a lot of adhesive residue, but no apparent damage to the membrane.
It cleaned up OK, with just a small nick on the V key.
The membrane tails looked in reasonable shape, but there was some cracking visible, and several half rows of keys were not responding.
For reference, from left to right, in the orientation in the above photo, the signals on the 8 way connector are:
- B N M . Space
- H J K L New Line
- Shift Z X C V
- Y U I O P
- A S D F G
- 6 7 8 9 0
- Q W E R T
- 1 2 3 4 5
Next is the 5 way column connector
- 1 Q A Shift Space New Line P 0
- 2 W S Z . L O 9
- 3 E D X M K I 8
- 4 R F C N J U 7
- 5 T C V B H Y 6
When the cracks are close to the end of the tail like that, you can sometimes fix it by shortening the membrane.
I tried that out, but I was still missing some keys. There must be another crack in the membrane tail somewhere.
The tails were still mostly flexible, so I gave it a go. Some of them go brittle and it's not worth even trying. You get others where the cracks are right at the point the tails go through the case, and likewise it's a non-starter.
I did have a new membrane lined up ready, but I was hoping to keep the original, if I could.
It took a couple of goes, but I was able to trim back the membrane past the damage and get all 40 keys working.
The tails are shorter, but still long enough to work with.
Testing that out, all 40 keys were working. Now don't move anything!
The Case
The case I found with these boards was not pretty.
The top half of the case was not in good condition, it was a bit patchy and when I tried to clean it, I was getting black on the paper towels.
I tried to use it for photos of the Minstrel ZXpand II, but it looked awful.
It is like someone had partly pained it black or sprayed it with acetone or something? And the red had mostly worn off the "ZX81" raised lettering.
I tried various cleaning products I normally use for cases, from kitchen cleaners to car dashboard cleaners, even bumper restorer.
A bit better, but not great.
The patchy section of the case is still evident, I don't seem to be able to get rid of that.
I don't know if it is the result of some previous cleaning attempt, or maybe caused by overheating as the regulator and heatsink is just below?
The cleaning had removed the last traces of the old red lettering.
I tried repainting that a couple of times, I am still not happy, but it's passable.
In the past I have done these with aircraft model enamel paint and a tiny brush, I think I need to try that way if my eyes are still good enough.
Putting it all Back Together
There are lots of screw holes on the board, but only two of them are used at this stage.
I have highlighted them here. The other screws are meant to go through the bottom of the case.
I marked those on the silkscreen of the Minstrel boards, as seen in this one from the white case (since I had that folder of photos open already).
The back attaches with five more screws.
Three of those are hidden under the feet, so I will wait until I am sure everything is finished before I fit those.
Testing It Out
The final result is looking quite good if you get the angle right to minimise the blotchy bit.
It all seems to be working.
I now can take some better photos of the Minstrel ZXpand II.
All working nicely.
What Next?
I am not sure what else I can try to restore the top of the case. I think it is probably OK as it is now.
I was originally considering having a go at sanding and painting the case black, although it might be easier to see if I can find a more photogenic case.
Or should I make another white one?
Either way, the ZX81 side of it is working nicely, and the upgrades should serve it well for a long life. I might even treat myself to one of the vLA81 ULA replacements.
I might have a go at the third board, I expect that will be the same, just replace all the sockets. I don't have any more working ULAs, so I will need that replacement. Then maybe I can leave the third board as a 1K ZX81 with original chips and UHF TV out as a sort of reference?
Any other suggestions?
All items are still available, and I can ship worldwide.
Including the Minstrel 2 and 3 which are available in versions which will fit in a ZX81 case as a drop in replacement for the ZX81.
The Minstrel 2 is ZX80 level, no NMI compute and display (slow) mode, but 16K of RAM.
The Minstrel 3 is ZX81 compatible, with slow mode and 32K of RAM to allow high resolution graphics.
The Minstrel 2, 3 and Minstrel 4th (Jupiter Ace / ZX80 / ZX81 / Lambda 8300 / RC2014,) are available with built in keyboards
All versions are available in kit form, or pre-built, and optionally the new Minstrel ZXpand II SD card and joystick interface.
International shipping is a bit complicated at the moment, so if you want to order from outside the UK, please contact me using the contact link at the top of this page.
See here for more information:
Sorry to have to do this, and I know this is going to affect sales, but please understand it is the only option I have right now.
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