CPC464 Some keys not working

[Macc]

Definitely not membrane, wondered what it could be?

[morley27]

Sounds like a motherboard problem, Locating what causes the fault is beyond me, there's lots of people on here though that should know, maybe one of the chips are faulty.

[Munchausen]

I think the AY (audio chip) is what connects to the keyboard. If it isn't the membrane and some keys are working, I'd say it has to be between the connector and the chip itself... you could try checking for continuity between the connector pins and the pins on the chip? Suspects are the solder joints on the AY, the traces between the connector and the AY, solder joints on the connector, and the connector itself.


Are you sure the membrane is OK? And the connector and cable coming out of the keyboard (actually part of the membrane I think) is also OK? How did you verify this? (because a membrane fault seems more likely to me).


I'm not an expert on CPC hardware though. Gryzor? Bryce? TFM/FS?

[Macc]

Cheers guys will give that a go!

[TheCorfiot]

Cheers guys will give that a go!

If you find you do need a membrane, give me a shout 

[Macc]

Thats good to know for the future!  I know its not the membrane though as the keyboard works fine if its plugged into another machine and a known good membrane does exactly the same in the poorly board.

[Marq]

Are they just some random keys here and there or clearly a row or column of consecutive keys?

[Macc]

Without re-assembling the whole thing and finding a keyboard for it (its just the board at the minute thats been on the "for spares" pile a while) I cant remember for sure but I think it was the same ones every time

[endangermice]

I had this exact problem on an Archimedes A3000 I fixed a few months ago. The tracks had been eroded by a leaky battery. I used the schematic to repatch the tracks between appropriate solder points. Obviously the CPC won't have died due to a leaky battery but the repair technique is much the same.


You'll need a copy of the service manual for your machine which you can get from this very site (just do a search) some thin wire, soldering iron and a continuity meter to establish chich tracks are broken.

[00WReX]

This may be worth a read...

6128 keyboard woes *** SOLVED ***

I also posted up the keyboard switch matrix & connectivity to the AY diagrams within that thread.

Cheers,
Shane

[Macc]

Thanks guys, food for thought right there, ill see where that takes me!