Repair SGI clock modules

This page last updated Jan 1 2020 Contents (c) copyright Herb Johnson 2020. Check my SGI Web page for various SGI parts I have, and discussion of how SGI systems use these modules.To email me or to order follow this link.

SGI Indy, Dallas non-volitile RAM chip repairs for dead battery

The following are my notes in 2010, from an SGI forum on - "SGI/Getting Started" subject "NVRAM battery......" Unfortunately by 2020 the Web domain is gone.

photos: dallas_1.jpg dallas_2.jpg

The Indy uses a small RAM with battery to keep vital information, and to run the time of day clock also in the chip. Thos chips are usually Dallas brand, and in black epoxy packages slightly larger than ordinary IC's. This note describes a fix to replace the battery in the chip. Typical Dallas numbers for the device are: DS1386 (8k-150 RAMified Timekeeper), DS1397, etc. Find the documentation for your chip, so you can determine which IC pins correspond to battery power. Typically a battery cell is mounted near the top of the package, and wired to those IC pins. It's suggested that a magnet might be used to find the battery in the package.

One fix is to find the pins that correspond to the internal battery; file the package on the side above both IC pins, sever the connection to the internal battery cell, and solder in a battery holder atop the package. Another method is to grind away (Dremel tool) the top of the package above the battery and work on those conections, possibly remove the old cell which is soldered in.

A CR2032 socket provides a means to use a watch/coin battery without soldering leads on it. You can buy coin batteries with leads but not at Radio Shack or other local stores.

Another fix, is to replace the TOD module. But many of these are out of production models, or just too expensive. My good friend Jon Chapman AKA Systems Glitch, builds his own from surface-mount Dallas versions. He also offers a battery "cap" you can hack into dead-battery modules. Check is pages for various Dallas/Maxim replacement or battery modules.

- notes by Herb Johnson

Herb Johnson
New Jersey, USA
follow this link to email @ me

Copyright © 2020 Herb Johnson