Salvaging original keyboards

Discussions about Sinclair ZX80 and ZX81 Hardware
patters
Posts: 122
Joined: Thu Mar 11, 2021 12:34 pm

Salvaging original keyboards

Post by patters »

On one of the ZX81s I bought, the keyboard ribbon has only snapped at one edge, across the line of where it entered the connector on the board. Not sure if it's normal, but the two separate ribbon tails appear to have delaminated all the way up the length of the ribbon. The break happened when I very gently disconnected it and fortunately it did come out without leaving a piece stuck in the socket. Other than that it seems fine. It still flexes fine without shattering (unlike my Spectrum one). I figured I should probably try to salvage it since apparently the repro keyboards are less responsive. I can then keep the repro I ordered for the day it does eventually give up.

When trying to insert it just lightly enough to test my WESPI handiwork I found that the material is very thin indeed and flexes too easily, and seems likely to snap again during a proper insertion. Is it worth trying to reinforce this when I trim it, say with some tape, or some very thin stiff clear packaging plastic on the back side)? Or will this splay the connector too much and make its 'bite' worse when I come to replace the membrane altogether? I notice that modern flex connectors do have stiff reinforcing at the insertion points for instance.

Is there an established method for continuing to use original keyboards? My latest idea is to use the thinnest packaging plastic I can find, like a strip from the lid of say a blueberry punnet, and using that as a stiffener backing to guide the end of the ribbon into the jaws of the connector, and then perhaps sliding it out once the connector has its grip on the ribbon.
User avatar
1024MAK
Posts: 5103
Joined: Mon Sep 26, 2011 10:56 am
Location: Looking forward to summer in Somerset, UK...

Re: Salvaging original keyboards

Post by 1024MAK »

Yes, use the thinnest piece of plastic that you can find. But don’t tape or glue anything to the membrane tails/ribbons.

Use your thin piece of plastic to help guide the membrane tails/ribbons into the connector, then while holding the membrane tails/ribbons, carefully remove the plastic. By doing it this way, you can use the thin plastic to slightly open the contacts so that they don’t damage the membrane.

Mark
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp

:!: Standby alert :!:
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb :!:
Looking forward to summer later in the year.
Moggy
Posts: 3231
Joined: Wed Jun 18, 2008 2:00 pm

Re: Salvaging original keyboards

Post by Moggy »

I can only comment on the replacement ones sold by Sell My Retro.

The very early ones that were sold there were quite awful and felt like pressing a brick and I was very critical of them.However Rich Mellor took this on board and the ones he sells now are excellent in my opinion having a thinner top layer with a good keypress feel that gets better the more they are used and having better made plastic ribbons.

The ones sold for the ZX80 I have to say are just horrible to use having the same brick like feel needing a very hard press especially with shifted keys and to be honest I regret changing mine.
patters
Posts: 122
Joined: Thu Mar 11, 2021 12:34 pm

Re: Salvaging original keyboards

Post by patters »

The guy did the comparison video I linked this time last year, so AFAIK no one has produced any membranes since then. Anyone who's restoring a ZX81 is very likely to also be a pedant :lol: so I think it's probably best to try and salvage where possible, and only fall back to a reproduction when it's inevitable. I ended up buying the PureRetro ones purely because RWAP has run out of stock with no ETA on new ones due to Covid disruption. I thought it would be just my luck for the other vendors to run out too, so I pounced. Although they have a pixel missing from one of the keys I do like that the typeface of the keys will be more accurate even if they cost a bit more. As the chap in the video says - when you're going to the considerable effort of organising the manufacture of a reproduction why on earth would you select the wrong main font and weight, and the wrong size for the red characters. Surely this would be relatively easy to correct in subsequent batches, but maybe they made a huge run in 2014 and none since then (since that's the date on them).
Last edited by patters on Tue Mar 30, 2021 3:11 pm, edited 1 time in total.
Moggy
Posts: 3231
Joined: Wed Jun 18, 2008 2:00 pm

Re: Salvaging original keyboards

Post by Moggy »

As you say only a pedant would balk at a slightly out kilter typeface the rest of us happy just to have something that works, and I'm fascinated by those same pedants who are happy to use newly designed ULAs and a composite mod! :lol:

As I said I can only go by my own experience and YouTube videos not withstanding the Sell My Retro ones when available are the ones to buy.
patters
Posts: 122
Joined: Thu Mar 11, 2021 12:34 pm

Re: Salvaging original keyboards

Post by patters »

I guess it's when you consider quite how much work is involved to manufacture anything (see the many Spectrum Next blog posts), that it seems so silly to get the lettering wrong. Especially considering how much stuff went right. I mean even the graphic characters must have been very difficult to print.

My Zeddy now has a WiFi interface. Not exactly stock :lol:. Then again I have no sentimental attachment preventing me from modding a ZX81, as my first computer was a Spectrum. I'm just here for the fascinating lo-fi games in the face of ridiculous technical constraints.

In comparison several years ago I bought a fixed GAL chip (unrainer mod) for my 128K toastrack and have been too scared to fit it. I didn't want to risk my first try at soldered chip removal wrecking a £200+ computer. However, now I've cut my teeth on 16K upgrades for two cheap Zeddies I may give it a go...
Moggy
Posts: 3231
Joined: Wed Jun 18, 2008 2:00 pm

Re: Salvaging original keyboards

Post by Moggy »

Also to add that the little "indentations" the you-tuber goes on about (in that horrible smug self aggrandised look-at-me- I'm-an-expert patronising half giggling manner a lot of these people seem to have) appeared on mine after about three weeks and are just as responsive as the originals in use so perhaps if he had done more typing and less pissing about with a micrometer he would have realised that, he has to be the most pedantic bloke I've come across with too much time on his hands,speaking of which he does seem rather fond of showing them off. :lol:

As for your endeavours Patters it seems we are bed fellows in the modding regard and the fact you have wi-fi sticking out the back of the zeddy is heartwarming.

More power to your iron sir!! :lol:
Last edited by Moggy on Tue Mar 30, 2021 3:34 pm, edited 2 times in total.
patters
Posts: 122
Joined: Thu Mar 11, 2021 12:34 pm

Re: Salvaging original keyboards

Post by patters »

It doesn't even stick out. That's the beaut. The antenna is on the PCB. The ESP32 is incredible really. £7.50 and it can even run Doom!.
Moggy
Posts: 3231
Joined: Wed Jun 18, 2008 2:00 pm

Re: Salvaging original keyboards

Post by Moggy »

patters wrote: Tue Mar 30, 2021 3:23 pm It doesn't even stick out. That's the beaut. The antenna is on the PCB. The ESP32 is incredible really. £7.50 and it can even run Doom!.
SOLD!!!
User avatar
mrtinb
Posts: 1906
Joined: Fri Nov 06, 2015 5:44 pm
Location: Denmark
Contact:

Re: Salvaging original keyboards

Post by mrtinb »

My first project for the ZX81 was to build a custom keyboard. Even though it was terrible, it was better than the original one. My second keyboard was bought from ZX-Team in Germany which is a PCB for cherry switches. This is my keyboard today. The next project I'm working on, is building my ZX81 into a French Minitel terminal. I currently program a microcontroler to remap the keys. I still have my original broken keyboard laying around, when I can't remember which key to press, as my current keyboard only has regular keycaps with letters and numbers.
Martin
https://zx.rtin.be
ZX81, Lambda 8300, Commodore 64, Mac G4 Cube
Post Reply