25C rememberss data only


Hello all,

My 25C's been acting funny. Seems that only data is retained by the constant memory but not the program memory. Another funny behaviour is that CLEAR: PRGM fills the program memory with keycode 40.

Any thoughts



I have one with the same problem: fried RAM chip. No way out but finding a donnor with a good one...


Luiz (Brazil)


Thank you. I'm sorry for not mentioning that when I got the calc, Dad wanted to see the calc. I thought it was so that he could operate it so, I turned it on. Well, dad knows I have trouble opening the battery door so, unannounced, he opened up the battery door while the 25C was turned on. Perhaps it was my fault for 1--turning it on thinking dad wanted to operate it and 2--not asking him first what he wanted to do with it.

So, could that mishap of leaving the calc on while dad was opening up the battery door be the source of the problem?

Edited: 14 Apr 2012, 4:07 p.m.



Did it happen while the calculator was connected to the charger?



Hi there. Nope. Got the calc in the mail. Dad wanted to help me open the package. So, after he opened the package and since he knows I have a little trouble opening up Woodstock battery compartments, he decided to help me open it. In so doing, unbeknowst to me, the calc was on while he opened up the battery door. So, it seemed that may have cause a short or power surge.

BUT!, as you'll see in my latest post, the batteries were already corroded and perhaps that and not the battery door opening while the 25C was on is why the 25C was going haywire. I'm not certain but, my hunches tell me that the battery corrosion is the issue. But, your insights would know better than I would.

Edited: 15 Apr 2012, 9:37 p.m.



Removing the batteries while the calculator in ON, PROVIDED THAT THE CHARGER IS NOT CONNECTED, has no harmful consequences. Memory contents may be lost or corrupted (not memory circuits) if you replace the batteries right away, but apart of that, it would not destroy its circuits, even if there is some corrosion due to battery leakage. If you keep the batteries out of the calculator for a while with the power switch turned to ON will only discharge all capacitors and make sure memory is cleared. If the calculator insists on not keeping memory contents (either data or program), then a fried RAM is the most likely cause. Another valid chance, mostly in this scenario, is cooper trails shorted by cooper oxide under the IC's. Removing them, cleaning and reassembling might solve the problem. As I mentioned before, I restored some Woodstocks back to life this way,


Luiz (Brazil)

Edited: 15 Apr 2012, 10:07 p.m.


Thanks for that reassurance and very thorough explanation. But, what would have caused keycode 40 to appear in program memory in each program step after I turned the calculator back on after entering a program and shutting the 25C off?


Hello all.

Well yes, this was my original update:

Turns out, after I ejected the battery pack, I found that the batteries (at least the exposed side that meets the battery contacts) has some corrosion. Although I did clean the battery contacts with the distilled vinegar, I'm inching towards the hunch that it's the batteries' corrosion that's the culprit.



after a couple more days of using the 25C and a heavy dosage of heightened optimism, my 25C is an amnesiac once again, even to the point of the keycode of 40 at each program step. So, I should resolve to cut my losses. In a better light though, I should consider this machine as nice spare. It works as a 25 for everyday use but it's not a museum piece.

Edited: 17 Apr 2012, 2:20 a.m.

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