membrane keyboard for CPC Plus

[Sid_]

Hi all


my keyboard membrane of my 6128 Plus start to dysfunction. And some keys does not respond anymore.
I will try fix it with this product : https://www.amazon.fr/gp/product/B00OZATJ3A/ref=ox_sc_act_title_1?smid=A337FVOX35P1H8&psc=1


But someone may sell me a keyboard membrane for Plus series if you have spare ?




Sid

[gerald]

Hi all


my keyboard membrane of my 6128 Plus start to dysfunction. And some keys does not respond anymore.
I will try fix it with this product : https://www.amazon.fr/gp/product/B00OZATJ3A/ref=ox_sc_act_title_1?smid=A337FVOX35P1H8&psc=1


But someone may sell me a keyboard membrane for Plus series if you have spare ?




Sid

You may have go to the http://quasar.cpcscene.net/doku.php?id=electronique:reparation_clavier_cpc_plus method

[Sid_]

Yes, I already did it    and that during this operation I decided to clean the keyboard membrane with alcool.
I'm pretty sur I forced a little bit on the membrane.
And all the keys on a track does not function any more (R,E, Escape, Arrow down, F0, Return, : , U , Y)
The answer time is quite good now for the others.

[Sid_]

I'm checking all the membranes, and it seems not to be the keyboard the issue.
Someone can sell my an AY38912 and a socket ?
@Bryce have you got some spare items ?


Regards.

[Bryce]

Are you sure it's the AY? Have you checked the outputs from the ASIC?

Bryce.

[Sid_]

Nope
I can only check the continuity. Which pins must I check on the asic ? 

[TotO]

And what about the continuity of the membrane? (at less on the connexion side)

[Sid_]

I'll check all the connections of the membrane.
Stay tuned ^^.

[GUNHED]

I'm checking all the membranes, and it seems not to be the keyboard the issue.
Someone can sell my an AY38912 and a socket ?

These breaks on the membrane may not be obvious. If some keys still work and if you don't get some characters on screen after switching on the CPC then the AY will be fine in 99,97% of all cases. 


In my case tipping on Plus key made it work a bit again. Problems occur with the 6128 Plus after not using the keyboard for some longer time. Then just start typing on it again, and it will work better. (I really hope).

[Sid_]

I did some tests.
My voltmeter beeps when the value is lower to 50.
All values on this membrane between silver spots is almost 20.
When I measure between connector and a key sliver spot the value is 120 and even greater.
What is an acceptable value ?
And to fix it, must I draw a silver line between key spot ?

[Sid_]

I forgot to say that all the tests from Arnold diag are successful (not the keyboard obviously).

[Bryce]

Pins 71 to 88 of the ASIC should be outputing a pattern (each pin goes low for a short period one after another). You need to check whether this is happening. Also, be careful when measuring the membrane with a meter, those metal probes can easily damage a perfectly good membrane.

Also, which keys aren't working? This can be a good indication of what is broken.


Bryce.

[Sid_]

here the keys does not function :
- CONTROL, W, X, V, SPACE
- R, E, ESCAPE, flèche du bas, F0, RETURN, : , U, Y
and on the matrix :
[/code]
                          UNDER              OVER
                           FLEX                  FLEX   
ESC                     X3                       Y9
E                          X3                       Y8
R                          X3                       Y7
Fléche du bas      X3                       Y1
F0                        X8                        Y2
RETURN             X3                        Y3
U                          X3                       Y6
:                           X6                        Y4
Y                          X4                        Y6
W                         X4                        Y8
X                          X8                        Y8
V                          X8                       Y8
SPACE                X8                        Y6
DEL                     X8                        Y10

Code Select Expand




[size=12px][font=helvetica]Can you guess what's wrong ? [/font][/size]

[Bryce]

That looks like there are multiple breaks in the membrane. If the AY or ASIC was damaged, then if any key on X6 doesn't work, then NO key on X6 would work. The same for the Y grid.

Have you cleaned the membrane and the membrane sockets?

Bryce.

[Sid_]

I juste clean the membrane, I 'll do the same on the membrane socket. Thanks @Bryce

[Sid_]

I cleaned the membrane socket and the membrane, and the issue still occurs.
I bought another amstrad 6128 plus to test with a "new" keyboard.


I don't have the possibilities to test the asic, I just have a voltmeter.
Someone may fix this keyboard, amstrad plus ?


I don't want to let this machine unfixed, I own it for a long time ^^.

[Sid_]

I check the continuity between membrane slot (CP04 upper slot) to asic (pins 70-80) and it's ok.
I check the continuity between membrane slot (CP04 lower slot) to NR02 and it's ok.
What others tests can I do  ?

[Bryce]

You could use a piece of wire to short the pins (one from each socket) and see if the characters appear that the keyboard isn't showing. Then you'll definitely know whether it's the computer or the keyboard.

Bryce.

[Sid_]

I followed the @Bryce advise and I test the CP04 pins of the keyboard slots :
Here the results


Well I think the ay is bad. I ordered one with a socket, I'll replace the current with the new one and hope everything will be ok.

[Sid_]

Well after a while, I succeeded in fixing the issue.
When I removed the AY chip I found some missing tracks.
I added two wires to replace them, and now my CPC Plus reborn.
Thanks a lot to @TotO @Kris and @hlide for their patience and their advises.

[Bryce]

Thanks a lot to @TotO @Kris and @hlide for their patience and their advises.

Don't mention it...    Oh, it's ok, you didn't.

Bryce.