Keyboard troubles

[Lardo Boffin]

I thought I would start the hardware traumas off!

The keyboard worked fine on arrival and for a couple of days but today started acting up.

I realised when I went to type DIR and D did not work.

I went through all the keys and the following do not work:

S D F G H J

Z

Note that when pressing D the caps lock light toggles!

I have taken it apart since to evict a few dust bunnies and prod the back of the keyboard with a continuity tester.
As far as I can tell all the keys apart from Z have continuity when pressed.

Any suggestions as to where next?

Thanks!

Lardo

[vanpeebles]

Servisol Super 10 might work wonders and a ton of keyboard tapping.

[Lardo Boffin]

Servisol Super 10?

Tapping I can do!

Edit - just ordered a can.

[vanpeebles]

On an Electron I had, I eased off keycap, and depressed the plunger and worked in a spray of super 10 that way, I didn't bother pulling all the switches to bits.

[Lardo Boffin]

On an Electron I had, I eased off keycap, and depressed the plunger and worked in a spray of super 10 that way, I didn't bother pulling all the switches to bits.

Will give that a go when the spray arrives thanks.

Here is the keyboard:

0ED44089-DD7F-438F-816E-4DA9F765D5D6.jpeg (579.46 KiB) Viewed 13693 times

11D65F21-C9FC-4F4E-B81C-1039363BC431.jpeg (489.67 KiB) Viewed 13693 times

Didn’t want to risk removing the space bar. They are often a bit complex...

Is it possible to pull the keyswitches apart on these, should it come to that?

[jltursan]

You need to:

1) Desolder the switch
2) Pull apart the mechanism with a flat screwdriver. Be gentle!

This keyboard can be fixed 99% of the time...

[sirmorris]

Before removing keys can you please let me know if the A and F1 keys are similarly affected? It could be that there's a problem with the PSG chip, which is in charge of reading the keyboard. See the hardware manual, section 3.9. I've spent quite a bit of time there recently with biggoil. If A & F1 are similarly busted we can look at the connection to the AY. The keys are in a matrix and those keys are all on one matrix row, driven by output A6. This row's selector appears on pin 14 of connector M006.

[Lardo Boffin]

Hi sir morris!

Thanks for looking into this. So far I have checked continuity at the back of the keyboard. All the keys except Z show continuity at the back when pressed in. If I put the probes on the back of F1 or A and press the key I get a nice buzzing sound. I just get the sound of silence on Z.

I am wondering at this stage if the problem is with the key switch itself?

Below is a photo of the back of the Z keys pins.

261739B2-01A8-417C-800D-DACACF66B230.jpeg (746.97 KiB) Viewed 13677 times

[vanpeebles]

Did you work a load of super 10 into the switch?

[Lardo Boffin]

Did you work a load of super 10 into the switch?

Its on order. Should be with me mid week I hope.