4016 Keyboards

Process was (tedious):

1. Remove the keyboard from the bottom of the computer cover.
2. Remove the cable.
3. Remove the metal clip grounding the foil cover to the keyboard.
4. Wipe over the foil cover and set it aside.
5. Blow out the keyboard.
6. Remove the key caps with puller.  The spacebar requires two sturdy pairs of long nose pliers
7. Store springs.
8. Wash keycaps in warm soapy water using a soft toothbrush to scrub and allow to dry.
9. Once dry, wipe over once more with a damp cloth.
10. Blow off the residual loose dirt from the keyboard assembly
11. Desolder the caps lock switch.
12. Remove the pcb screws.
13. Clean the pcb with paper towel and IPA.
14. Remove and store the caps lock switch (2 little levers).
15. Store the barrels and keypads.
16. Scrub the key frame in warm soapy water.  Blow off and allow to dry.
17. Wash the barrels in warm soapy water and allow to dry.
18. Scrub the cable in warm soapy water, blow out, and allow to dry.
19. Put the rubbers in a container and shake off as much dust as possible.
20. Clean both sides of rubbers with cotton buds and IPA.
21. Put the barrels back in the key frame and insert the rubbers.
22. Clean them again.
23. Re-coat rubbers with conductive coating.
24. Inspect carefully for lint and remove.
25. Reassemble.
26. Test with harness and meter.

The conductive coating has to be mixed and then used within a couple of days so it makes sense to do both keyboards at the same time.

I did start with the second keyboard because it was in an awful state.

This is the first keyboard (from the cleaner machine).

The contacts were coated using a CircuitWorks Rubber Keypad Repair Kit.  This kit is quite expensive and a bit laborious to apply, but it does the job.  It looks like it’s using a silver paint.  The key resistances were very low.  There was enough in a kit to easily do the 140 or so keys.

The shift lock keys was not working.  While looking for a replacement online I found a video where the author had worked out how to open the switch by twisting the terminals, so I thought it was worth having a look inside.  It was filthy – I’m not sure how this much ick could get inside a switch with no significant orifice. 

It was built like a puzzle.  Cute little mechanism with lots of pieces.  After a clean, things looked better.

There is a spring as well – fortunately it was still in the parts container!

It took a while to reassemble it.  The pins screw through the contacts to create a hole and contacts at the same time.  I added some aluminium foil to make sure the contact was still good.  I was relieved to find that the switch was working.

Testing just requires a keyboard cable from the computer and a jig which joins all the columns to all the rows.  Then each key can be tried.  This can be done before putting all the key caps on by turning the keyboard upside down and pressing upwards.  Otherwise, without the caps and springs, all the keys are activated at the same time.