VOGONS

DALLAS DS12887A WORKS with 3V battery across the "CLEAR CMOS" pins.

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First post, by TerryKing

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Hello Everyone,

I've been following the "Old Motherboard with dead Dallas CMOS/RTC chips" conversations around the web. I had 3 old HOT555 socket 7 motherboards given to me a few years ago; I dragged them out. AND, the dreaded "CMOS Battery Bad" messages.

MUCH Later: I have mine working in a unusual and unexpected way. See:

https://arduinoinfo.mywikis.net/wiki/DS12887A … DALLAS-RTC-DEAD

Takes a few DAYS but then WORKS FOR ME!

Let me know if anyone else is successful with this.

Last edited by TerryKing on 2022-07-23, 19:08. Edited 1 time in total.

Regards, Terry King
...In The Woods In Vermont USA
The one who dies with the most Parts LOSES! WHAT DO YOU NEED??

Reply 1 of 2, by majestyk

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Won´t work for long I´m afraid.

Regular lithium cells can´t be recharged properly and the battery pins are not reachable unless you open the case.
So I guess a little charge finds it´s way through the circuitry inside the dallas chip and "recharges" the cell with a handful of electrons.
Might work for a week or two...

The BIOS error disappears even when there´s only a very low voltage from the Li-cell, let´s say 0.5V instead of 3V. But the voltage will deteriorate quickly and fall below the BIOS threshold and the error will be back.

Reply 2 of 2, by TerryKing

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Hi,
Well as us Oldbie's (Years >= 80) say, "Time Will Tell".. I'l l update if I have something to Tell...

Thanks! I plan to leave the 3V connected there... I'll put the 3V on another identical motherboard, wait a week, and temporarily DISconnect the 3V and see what voltage (if any) is there...

Regards, Terry King
...In The Woods In Vermont USA
The one who dies with the most Parts LOSES! WHAT DO YOU NEED??

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