HP-21 Disassembly Help...

[Geoff Quickfall]

That's a good one Katie, but not all Woodstocks have the holes! My five 21 boards do not have the holes on the reverse side of the keyboard under the domes. My 25, 25c, 27, 29 all have those pores we are familiar with. For some reason the 21 does not.

No holes in 21:



Holes in various other HP family boards:
Red arrows pores, yellow arrows snap domes




I was going to suggest the wire trick but only after drilling a tiny hole underneath the offending dome on under side of the keyboard. I want to get home to try it before telling Jeff to attempt it.

Jeff, if you are willing to attempt a drill before I get home, I suggest getting the finest bit you can get, 1/32nd, 1/64th. If you have a Dremmel stand and are able to set the drill depth then that is the best option. You just want to drill the PCA board and not any deeper. If no stand I would take the bit in a pin vice and drill with your thumb and fore finger, only a drill bit then just the drill bit, thumb and forefinger. Looking at the PCA board you can see the black rivets. You can also see round contact traces residing directly under the snap domes on the underside of the keyboard PCA. I would drill to one side of the round snap dome contact trace that you can see.

I use deoxit red which contains a solvent which is safe on all plastics and a deoxidant, then as Katie mentions, introduce a fine bent wire into the hole and twirl it cleaning any oxidation.


Hope this helps.

On a different note in lieu of the fact that I won't be home on the 1st of next month. Just finished a chapter allowing the creation of this: