[HP-35s] Are bad keys fixable?

[Marcio]

Jeff,

After much consideration, I decided to buy yet another 35s unit (the 2nd second-hand one, 3rd overall) a couple of days ago. There were several bad keys on this one. Some needed much more force to respond, namely COS, SQRT (required a very firm press, much like the R/S on the 2nd one), y^x, +/-, E, () and 8. So 7 keys overall. I noticed these keys are close to each other so I suspected there was something other than low quality causing all that trouble. Long story short, I gave the 35s a good bath with regular alcohol in a plastic bowl, and was careful to save the display. Well, I was actually surprised by the amount of residue resulted from the manufacturing process, should have taken a picture.

Well, I am happy to report the 35s is now fully functional (let's hope it stays like this long enough to justify getting another one) and the other one with the bad R/S key is gonna take a bath as well.

To remove moisture and related, I let it rest for 24 hours, disassembled it and used a hair dryer to speed up the drying.

Also noticed the capacitors are different on the these machines. HP was able to change the hardware but not the software and it's been almost 10 years since introduction. If only the bath could wash out all those bugs as well.

Thanks.