Here is the part of the email Michael sent to me telling me the good news that my 25C lived:
"Well, I have an interesting story for you. There was a good deal of corrosion on the 25C's circuit board, even some on the keyboard traces. I removed some from the board with the dremel brush and put De-oxy solution on it. I reassembled it, resigned to it being non-programmable. The memory chip didn't look to have anything physically wrong with it. I modified and cleaned the battery pack. Then I sat down to write you an e-mail.
While playing with the calculator, trying to program it... suddenly it started showing random keystrokes in program memory. O.K.... that was weird. Then, I could clear out memory and it seemed to take a few keystrokes! O.K.... then, it started working! I didn't want to push my luck with the board as the 25C's are so sensitive, so I didn't want to disassemble it again. But, then it started to malfunction again. So, I decided to take the chance and took it apart and re-soldered the memory chip and the ROM chip.
OMG... you have a fully programmable, fully functional 25C. Here's my conjecture: The Deoxy solution had some time to improve conduction somewhere just enough to make it work intermittently enough to alert me to it's possible survival.
I plan to play with it a little more while I clean the front with the usual Armor-all scrub. Looks as if I'm 2 for 2 for bringing these to life. Good feeling for a doctor."
A good story. Hopefully, it helps other people to fix those dead calculators that are out there on the "parts piles"