Yesterday I turned on my HP-25C and discovered that the contents of program memory and the storage registered had been lost. Thinking it was just a low battery, I replaced it with a fully charged NiCad battery pack, but still CMOS memory would not retain any entries. Even with the calculator powered on, I could not store data in any of the registers or a program. Also, statistical operations would not function properly, as they rely on the contents of the storage registers. This calculator has not been subjected to the killer AC adapter, since I charge the batteries externally, and only operate the calculator from batteries, so I don't think this failure is the result of any abuse or misuse. Has anyone else on this forum experienced this type of failure?
The CMOS memory has died in my HP-25C
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06-05-2010, 05:21 PM
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06-05-2010, 06:08 PM
(added: I checked Eric´s HP Calculator Chips and I would like to call your attention to some data I posted. I seem to have seen some ACT chips elsewhere, but chances are that I mixed the pictures. Please, follow Eric´s link and confirm.) Hi; I bought an HP22 some weeks ago and it has the same problem. I could also buy two HP25 and three HP21 that are not working, and along with some previous pictures I kept from other HP25, HP22 and HP21 I was able to repair, I consolidated some information. Both HP22 and HP25 use the same PCB layout and differ only in their ROM chips. I found that three of the five IC´s in these calculators have the same codes. The ACT varies from some models, and I collected these codes: 1820-1523Display driver appears in all three of them with the code: 1820-1382ROM chip varies: 1818-0163 + 1818-0164 for the HP22 (found in two different units)I found the same RAM chips in both the HP22 and the HP25 (the HP21 seems to use available ACT registers only) 1820-1564I also happen to have seen an HP25C with two RAM chips but their codes were not visible. In another HP25C there is a RAM chip written: HP5061-0469 2That is all information I have so far. Please, if there is something else to be added, I'd appreciate. If there is more information about this somewhere else, please, point the addresses out! AND if I messed some information up, PLEASE, point it out! Cheers. Luiz (Brazil)
Edited: 6 June 2010, 12:19 a.m. |