ZX Spectrum +3 keyboard

[ZxSpence]

Before xmas I took a punt on a zx spectrum +3 over facebook and it arrived after 2 weeks with the power cord snipped. Screenshots showed the boot menu, so assumed it was working. Anyhow, I had bought spectranet clone, and zx vga joy as well as an rs232 cable with the intention of working on a port of a previously abandoned game from another broken bit of retro hardware (spoiler alert).

Anyhow, plugged in zx vga joy, booted up, nasty sound from the +3 drive, but as I have no disks anymore not bothered, was going to go via spectranet for everything. Got the menu screen, no keyboard response. A few resets later got vertical bars most of the time and then back through to the boot menu.

I tried resetting with break held down, and it went into the signal tuning pattern as expected, then tried the combination of keys to get into diagnostics (service manual) and won't do it. So, clearly something wrong with the keyboard.


I took it apart, inspected the membrane connectors (seem fine, no cuts) and re-connected it up again, and still no joy.

Then I assumed maybe DPD had given it a battering so checked all the chips were seated (yep).

So, wind knocked out of the sails on this one, doubt I'll get any joy out of the seller, but what worries me is I've looked for +3 keyboard membranes with no success. I see there's a couple of repair places (Mutant Caterpilar for example) which seem promising, but is this worth the investment? Would they be able to fix it? They seem busy from their website (good 6 weeks turnaround) but no +3 membranes - advice I've read is if you want to replace it just buy a working +2! What if its not this?

What would you do? Is it like a CPC in that just giving it a decent clean fixes most problems, or is this serious and terminal?

[Guesser]

Have you stripped the keyboard down, given it a light wipe, and put it back together? That's usually all they need.

[ZxSpence]

Thats good news, what would you recommend using to wipe it down?

[Guesser]

Just a soft cloth I suppose. Maybe an alcohol wipe?

To be honest unless it's really filthy a big part of it is probably just taking it apart and putting it back together heh. Obviously if you get inside and the traces are corroded or something that's a different matter, but I think usually it's just the layers stuck together causing spurious connections.

[1024MAK]

Just a soft cloth I suppose. Maybe an alcohol wipe?

I’m not sure about using an alcohol wipe. It’s best not to use any solvents (including alcohol) of any kind except a damp cloth moistened with soapy water.

Elsewhere someone tried using a solvent to clean a membrane and found out the hard way that membranes are permanently affected (as in, damaged) by some solvent cleaners.

Don’t worry about getting it wet, as long as water does not get trapped in between the layers. But do ensure that it has completely dried out before refitting it.

A ZX Spectrum will ignore the keyboard if a key (other than a shift key) is continuously making contact (as if a key was stuck down), so it may also be a mechanical problem with one of the key mechanisms.

Because the +2 and +2A/+2B/+3 membranes are normally long lasting and generally reliable, there is insufficient demand for replacements, hence no market for them.

Mark

[Guesser]

It's so long ago that I last had my keyboard apart my memory's a bit hazy to be honest. I think I probably ran it under the tap or dumped it in a washing up bowl with all the key caps and everything else

[Guesser]

Because the +2 and +2A/+2B/+3 membranes are normally long lasting and generally reliable, there is insufficient demand for replacements, hence no market for them.

I still think someone could kill two birds with one stone by having a run of alternative membranes made with a less infuriating key layout. That would both make me happy and also free up some originals to use as replacements for anyone who wants to preserve the originality of accidentally hitting EDIT while trying to type anything. The seller could offer a part exchange

[1024MAK]

Well, if someone can get me a TARDIS, I’m willing to go back in time and argue with Clive about the keyboards on his machines

Mark

[spider]

Well, if someone can get me a TARDIS, I’m willing to go back in time and argue with Clive about the keyboards on his machines

Mark

I do wonder if the ZX81 (and to some respects the ZX80) would of benefited from the 16/48 Spectrum rubber keys. Food for thought.

Thats good news, what would you recommend using to wipe it down?

The last time I did this on another machine I used those 'baby wipes' , the rectangular pack of 50 or something for a £1. They don't tend to leave any residue, sometimes use them to wipe the dust off my monitors too.

[ZxSpence]

Tried the baby wipe technique, although the keyboard and membrane is now clean, unfortunately it didn't work. To eliminate the zx-vga joy from being the problem going to order a scart cable.

[Guesser]

Are you able to generate keypresses bridging the keyboard contacts directly without the membrane installed?

[cj7hawk]

If you leave the keyboard unplugged, then power up, then plug the keyboard carefully back in, do you see a key being recognized? Might be a stuck key.

Also, what is the condition of the two silicon pressure pads that hold the two membranes together? You can get a lot of weird keyboard outcomes if they are damaged or missing. I had that problem with a keyboard I completely disassembled over Christmas, and it caused me no end of confusion until I realized one of the pressure pads had fallen out during reassembly, causing all kinds of issues. Mostly related to anything that wasn't one of the original 40 keys.

I also assumed keyboard membranes needed to be replaced by after some good advice from Mark, just worked my way through cleaning them very carefully. It even worked for a keyboard soaked in dried-up motor oil that had permeated the entire keyboard and glued most of the keys. It works well now. They are very hardy keyboards.

David