Amstrad 6128 plus keyboard problem

[Maniac]

I have a bit of an intermittent problem with my 6128 plus keyboard.

If I haven't used it for a while then some of the keys don't seem to work but more often than not Control-Shift-Esc doesn't work to reset.

The natural thing to think is that the membrane is broken but I've cleaned that. Also without fail if I unplug the keyboard from the motherboard and then plug it back in all of the keys work.

Does anybody here have any ideas as to what the fault might be and how I might fix it please? I'm guessing a new membrane might be the answer.

[Bryce]

It may just be a bad contact between the membrane and the connector on the PCB. Did you also clean this and inspect it for cracks or worn tracks?

Bryce.

[Maniac]

Many thanks Bryce. I haven't cleaned the connector to be fair. How would I do this please as its a bit fiddly? Is blowing enough or does it need isopropyl alcohol please?

[Bryce]

Don't try to clean the membrane tracks at the connector, just the connector contacts on the PCB. Some sort of spray contact cleaner or isopropanol would be best, but even jamming a piece of fine sandpaper into the slot might work if you don't have a spray.

Bryce.

[TFM]

I have a bit of an intermittent problem with my 6128 plus keyboard.

If I haven't used it for a while then some of the keys don't seem to work but more often than not Control-Shift-Esc doesn't work to reset.

Ha! I just have the same problem. ESC works, Shift works, Control works, ESC with one of the other works. BUT all 3 together don't work. And yes, I didn't use the 6128 Plus for several months. Also joystick right and up or down doesn't work at the same time.


Hopefully it's only dirt, and not an ASIC problem. The machine is never exposed to dust, so .... I'm a bit scared here....

[Maniac]

Ha! I just have the same problem. ESC works, Shift works, Control works, ESC with one of the other works. BUT all 3 together don't work. And yes, I didn't use the 6128 Plus for several months. Also joystick right and up or down doesn't work at the same time.


Hopefully it's only dirt, and not an ASIC problem. The machine is never exposed to dust, so .... I'm a bit scared here....

I've had the same issues with the joystick too but assumed that was a dodgy cable on the joystick. I've not had time to clean the keyboard contacts yet but will try it when I do.

[TFM]

Dear Lord. I _really_ hope it's only an dirt issue! 

[CraigsBar]

Yep I'll stake my last dollar on it being dust in the membrane (or praps time to get a new one)

[JLPedro]

Hi, if all the above fails I had problems in my 6128 plus with keyboard and joystick that were related to the AY chip, replacing the AY chip solved all.
Symptoms were machine booted fine then on basic random key strokes apeared , on game joystick not responding.

[TFM]

Thank you for the hint. But here the problem is (imho) that some key or key combinations don't work, while there are no phantom key presses (at least im my case).

[MacDeath]

sometimes just unplug then replug it and it goes well again for a long time... also check if not too much dust are between the keys and the membrane.

but yeah, to clean the "plug" is good too.

[Audronic]

@TFM


""Also joystick right and up or down doesn't work at the same time"

Would indicate that the AY-8912(a) is the culprit, as the keyboard is not in the equation.

Ray

[TFM]

Could be, since all single keys do work, but combinations fail. On the other hand DEL works sometimes. I will give it a good clean, then check for spare parts. But maybe somebody else will find the problem more quick, till May I will have no access to my Plus. 

[gerald]

Could be, since all single keys do work, but combinations fail. On the other hand DEL works sometimes. I will give it a good clean, then check for spare parts. But maybe somebody else will find the problem more quick, till May I will have no access to my Plus. 

Your symptoms look like a aging membrane. The DEL key is usually one of the first to fail as it's one of the longuest path and and once the resistance of the track us above a certain level, the key press are no more detected.
I would look for a new membrane 

[TFM]

Thanks. Looks like CPC6128 makes less trouble than the Plus. But hard to tell after a long time of using both. 

[Maniac]

So it's been a while since I originally posted about my 6128 Plus keyboard whilst I tried things out and then work/life took over.

Anyway I decided to get a new keyboard membrane from TradeInPost. I had hoped to get a full keyboard assembly as mine's dulled over time but they no longer have them in stock (I found this after a quick phone call, so ordered just the membrane - apparently their website is out of date as the person they had doing it did a runner and they don't have the details to update it). Once it arrived a couple of days later I replaced the old one and everything works again as expected including the joysticks!

Looking at the connector on the old one it looks like it's been damaged at some point (by me I should add) as it has a slight kink in it. They're not v robust as we know but I'm sure it wasn't like that when it first started to go wrong.

Having a fully working system again is great so worth the money. Thanks TradeInPost for having this stock as otherwise not sure what I'd have done.

[Skunkfish]

Sorry to drag up an old thread but I've had a continuing problem with my 6128 Plus keyboard over the past few years.

If it's not used for a short while (which frequently happens), some of the keys will no longer respond on the keyboard.

Escape, Control, Return and Enter are some of the repeat offenders.

Opening the machine up, disconnecting and reconnecting the connectors at the motherboard will normally fix the issue but it always reoccurs.

New membrane was put in a couple of years back but the problem still happens...

Any ideas?

[pelrun]

Might be a insufficient voltage problem. I had something similar with my 6128 where just a few keys had slightly too high resistance and therefore too high a voltage drop to be registered. Fiddling with the connector reduced the resistance temporarily but it wasn't until I increased my supply voltage by a few tenths of a volt that it became reliable again.

[Skunkfish]

Thanks Pelrun, I was almost thinking along the same lines. Will check the output voltage on the PSU and try an alternative to see if it makes a difference.

[CraigsBar]

I've had this on my Plusses over the years. and every time it's been a membrane.


I tend to find Crtl Shift ESC and the Delete key are the first to stop responding.

[00WReX]

Hi @Skunkfish.

Over the years and across a number of CPC's I have also experienced the same thing.
In particular I had a handful of 464's, that every time I got them out I had to remove and re-insert the keyboard connector to get all the keys working.

About 6 years ago I was reading up on techniques of cleaning cartridge connectors (for another system).
One of the ways was to fold some cardboard and gently insert and remove into the connector.
This acts as a gentle abrasive (well not really abrasive) but almost, that can help remove any build up of contaminants.

What sprang to mind for me was that the CPC keyboard connector is basically a small cartridge slot.
So I tried this technique on them.

I created a notepad file with all the CPC's I had this issue with and noted the date when I cleaned the connector using this method.

I can honestly say that I have not had a re-occurrence of the issue after doing this.

Not to say that it won't re-appear at some point, but so far so good.

I even had a 464 that was so bad, that if I removed and re-inserted the connector, it would pretty much only be OK until the next power off/on.

After cleaning, it has been perfect since.

Attached is the black that came off the connectors (I used paper wrapped around cardboard to clean this one).

In hindsight, I believe that the majority of the issue is due to connectors actually being removed and re-inserted.
The black actually comes off the membrane connector/contacts.

The ones I've had the least issues with are the ones that have not been pulled apart (much).


Cheers,
Shane

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[Maniac]

The membrane does seem to be particularly delicate and if not used for a long while can cause issues. Taking the keyboard apart and cleaning can help as suggested by Bryce earlier in the thread but in my case the problem reoccurred. The replacement membrane has continued to work well but I suspect if I leave it long enough it may go the same way as the old one. Having said that it's not been in a hot loft like the old one which may have contributed to the issue by drying things out so the two bits of plastic aren't as supple as they should be for the contacts to work. As mentioned by others dirty contacts are a contributor as otherwise disconnecting/reconnecting would have no impact.


Sorry for rambling response.

[pelrun]

This acts as a gentle abrasive (well not really abrasive)

Paper and cardboard absolutely is abrasive - remember it's made of wood! Don't be fooled by the overall texture of the material; individual fibres are still quite hard and can damage fragile surfaces. There's a reason people who own expensive lenses are warned never to use tissues to clean them. (some ratbag used their t-shirt to clean the lens in my hackerspaces laser cutter, which was disastrous for much the same reason...)


However it's almost perfect for scrubbing contacts like this And it's a much safer method of reducing the total resistance than fooling with the membrane itself.

[00WReX]

Oh yes,  good point.  I was 100% aware of that.


I really meant this in the context of the contacts on the connector and that one or two insertions of the cardboard/paper would not damage the contacts as you pointed out.


And as you indicated, this is probably the least destructive thing you could try if you are having these sort of issues.
Just make sure the cardboard is not too thick.
I tend to cut up something like an old breakfast cereal cardboard box (using the non printed side).


Cheers,
Shane

[||C|-|E||]

Very common problem indeed, particularly with the Plus range. The cardboard method actually works pretty well though. At the beginning I thought that it was a membrane question but, as far as I have seen, it is the slot in most cases. I have a unit that had a membrane doped with silver but this did not improve things much (I mean, it failed after a few weeks). A new membrane was then put in place and symptoms reappeared soon enough. However, cleaning the slot with a little bit of cardboard worked for me too .