Quote:
Originally Posted by ScottishColin
OK - all keys, springs etc removed and thoroughly cleaned and dried. Keyboard PCB cleaned with 99& IPA (not the beer).
All back together and it doesn't half look nice (the PET keyboard could withstand a nuclear war I reckon). Most keys work and the ones that don't will get a layer of conductive paint in the next day or two on the pads that press onto the keyboard PCB.
However, most of the keys seem to give me the letter to the right. For example, 6 gives me *, J gives me K.
Where do I start with keyboard scanning?
Colin.
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Yes, I recall removing the keyboard's PCB with it's matrix of (gold-plated rather than a bit resistive conductive-carbon?) (with loads of tiny screws holding it) on a 3000/4000? series I used to have to fix the keyboard's non working keys.
And I just did what I do on remote controls units, cleaning the PCB with alcohol cleaning solution as well as the conductive rubber parts on the keys - Did you try cleaning those as well?
If all keys had worked when it was last working, then cleaning should be OK without needing to add extra conductivity to the rubber pads.
- Watching that Youtube video, I see he only checks the keys on a DMM (first on its continuity beep range, which often needs < 200R to sound), and after cleaning them he then actually measured resistance of around 1k on each
But he doesn't seem to check if that is actually low-enough for the computer to read them OK, before he silver paints them.
(I reckon it may well be, as many remote keypads also used carbon PCB pads / tracks, that were bit resistive)
So it depends on what pull-down / up resistor values are fitted on the 'output side' lines.
Getting incorrect key-press characters returned does seem a little unusual - Hopefully not one of the PIA / VIA's.
But a study of it's matrix schematic may help in working out what might be happening.
And I'm wondering if you may have the connector accidentally plugged in one-position out to one side?
Or maybe plugged in the wrong way round? (Doesn't look like it has a polarity key)