42s exit key repair by 17b

[hamishbarker]

My much used ("daily driver" calculator as a practicing formerly mechanical now structural and fire engineer) 42s developed the dreaded exit key fault. it would turn on but freeze up when trying to turn it off or use exit to exit a menu. Also the 1 key wouldn't work.

First I tried tweaking up the twist metal connectors, not successfully.

Eventually bit the bullet and removed the keyboard and tried new foam. that fixed the 1 key but not the exit key.

I saw a 10b locally for not quite a steal but bearable, as I assumed that the keyboard circuit is the same given the identical number and shape of keys. It looked pristine so I assumed that the keypad had light wear.

I was in luck, the part number on the flexible keypad circuit board is identical and the transplant worked.

I now have an apparently working 42s, and a dismembered 10b.

Things to watch out for:
- be very careful with the actual keyboard (the faceplate and flexible hinged keys) when it is disassembled. the key hinges are fragile. I broke my enter key. managed a fix of sorts with some super glue (cyanacrylate I think USA people call it?). It probably won't last but it was the best I could do.
- don't forget to clean the display glass when everything is disassembled.
- be careful not to break the tiny stake/socket clips along the sides. I had to hot glue my case back together (sparingly!).

[tcab]

Impressive bit of surgery - well done!

Now if only you could figure out a similar transplant process so that we could make the keys of our DM42 calculators nice, soft and HP-like. ?

[hamishbarker]

the enter key is loose again. It's going to stay that way since to fix it requires drilling out the epoxy I used to secure the membrane.

A couple of keys are not quite perfect. I should have set up clamping interior to the metal backplate not just at the edges while the epoxy set. They work but the action isn't quite as crisp as the 32sii I have for comparison.

It certainly is a committing fix to have to drill out the 50 or so heat stakes. But since the calculator was otherwise junk, there was nothing to lose.

It's such a shame that the 42s has no electronic interface. there are so many interesting looking 41 programs! I guess they don't take so long to key in...