HP25 suggestion for repair please

[murphy9]

This HP25 is behaving poorly - it's been in a box for 7 years and transported around the world US-> UK -> Australia. The 4 and 5 keys behave erratically, sometimes blinking but not registering a 4 or 5. Tapping 123456789 delivers 123656789 in fix2 mode, in fix8 mode the display registers 123666789 ! This was with new batteries. I've never used a charger.

The logic board has very minor oxidation around the battery terminal, but this doesn't seem to be anywhere else - I've cleaned it with the usual vinegar/ alcohol. Tracks that are visible look ok and none of the pads look like they have dry solder joints.

I've not touched the keypad (nor do I really want to if possible). Any suggestions appreciated for the next stage - worst case I'll put it to the side and wait for the Panamatik kit to become available again.

Thanks in advance Mark

[Steve Simpkin]

One easy thing I would try is to turn the calculator off and press each key on the keyboard dozens of times each. This has helped clear up non-functioning and bouncing keys on a number of Woodstock calculators. It may not help in this case but it is an easy thing to try.

[mfleming]

Another simple check if you care to open the case (sounds as if you have) would be to remove and reseat the display assembly and CPU board from their contacts.

[Maximilian Hohmann]

Hello!

(11-03-2022 07:15 AM)murphy9 Wrote:  ... worst case I'll put it to the side and wait for the Panamatik kit to become available again.

I don't think this is a candidate for a Panamatik kit yet. It rather looks as if a little bit of corrosion has found it's way underneath the 4 and 5 keys. There are holes in the keyboard PCB close to those misbehaving keys. I would pour some drops of contact cleaner into these holes and press the keys repeatedly to see if it gets better. Alternatively, if you happen to have another calculator from this series (it does not have to be a 25, any "Woodstock" will do) you can swap the keybords to make sure that the fault stays with the keyboard and not with the calculator.

Regards
Max