Hello everybody,
At first I really do apologize for my english (well, better than my school's english, but not perfect).
I have a problem with my oooold HP-29c that I would like to expose here :
I stored this little machine years ago, WITH the battery pack inside (approximately during 20 years). When I realized it was a mistake, I put it away (about 6 months ago); true, this makes 19.5 years of ignorance.
Well, I put a charger with the battery pack inside the HP, and observed some kabbalistic signs on the display, those who seem to indicate some corrosion problems. But in fact, the battery compartment was very clean. Pressing the keys just made the display a little more silly (or mad), so I decided to open the beast.
It was pretty clean inside: so I just cleaned the keyboard with white vinager (50% v, 50% water), letting it into this solution during 15 minutes, pressing the keys meanwhile. I changed the liquid, using only water, and rinsed the keyboard. Then I tried to use a (cold) hairdryer to dry it, but it had no effect since the keyboard is constituted of two very very close plastic panels. So I just let it in a black box, in the sun light (here it is summer, and the temperature in the box should have reach the 50 °celcius) during a whole week.
Finally, I reassembled the whole machine a week ago and it was OK! No more kabbalistic signs, keys were working for the best, and I even made a program to verify everything, and I was very, very happy (this machine belonged to my grandfather...).
Yesterday, I put away the battery pack to charge it in a HP-21. This is a pretty good battery pack for its age : while I am typing here, the machine is displaying Pi since two hours and a half without the charger.
But I just tried this morning to put it in the 29, just to use this machine a little more...
and then, after the usual 'error' message indicating the memory loss, the display and keyboard became one more time completely mad!
So what ?
- I can not believe this is a corrosion problem.
- I can not believe, (but I am not so sure) that the keyboard is so dirty that some dust has 'moved' in the machine last week.
But perhaps this is another thing that escaped to me. Perhaps battery requirements are different between an Hp-29c and an HP-21. Perhaps...
Well, if someone has an idea, or just want to suggest something... it would be a pleasure. Thank you for your attention.