Kjetil's Information Center: A Blog About My Projects

NCR System 3330 Dallas RTC Mod

The Dallas DS12887 RTC inside my NCR System 3330 PC had died a long time ago. Unfortunately, this made the machine unbootable from the hard drive, since it would forget the hard drive settings on each restart. Instead of finding a replacement, like for the Commodore PC 30-III, I opted for the external battery modification instead. I got this working with just two regular AA 1.5V alkaline batteries, a huge success!

The initial error on every startup was as follows:

NCR Battery Power Lost

Fortunately, the Dallas RTC is a in a socket on this machine, easily extracted:

NCR Dallas RTC Extracted

To perform the mod, two sections of the case needs to be opened, which I did with a Dremel tool:

NCR Dallas RTC Dremeled

Afterwards, it's possible to solder on leads for a new battery:

NCR Dallas RTC with new battery leads

I installed a new 2xAA battery holder inside the case, connected to the RTC:

NCR Dallas RTC external battery

The machine is now working again, settings can be saved to CMOS and booting from hard drive is possible:

NCR Powered On

Topic: Repair, by Kjetil @ 14/03-2020, Article Link