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AA battery in 4.5V battery compartment?
Posted by: 68kPlus on 2022-10-20 19:45:09
Hi everyone,
Just wondering if it's safe to use a 1.5V AA battery in a PRAM slot for the Macintosh Plus.
I tried and it and seems to work perfectly (I left it switched off overnight and it retained all PRAM data).

Just wondering if it will continue to work as expected. If this is the case, it will make a great bit of knowledge to know for all early Macintosh owners!
Posted by: thellmer on 2022-10-20 20:24:34
It certainly won't hurt anything...but I'd be surprised if it works reliably over time. Most of those old CMOS chips needed about 3v minimally to hold reliably and usually tolerated up to 7.5 or 8 volts on the upper end. But if yours is holding with 1.5 count yourself lucky. Once the battery stops dropping a bit it might start losing the settings but as cheap as 1.5 batteries are and easy to replace in the Plus you can definitely see how it works out over time.
Posted by: 68kPlus on 2022-10-20 23:25:42
Okay thanks for the info!
Posted by: rjkucia on 2022-10-25 10:52:15
That's surprising! 1.5 instead of 4.5 is quite a large difference. Does the clock run slow?
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