Gridcase 1520 CMOS Battery Replacement

Time to look at a Gridcase 1520 portable computer. Not the one that had the power supply failure; this is the cheaper model with the LCD screen instead of the gas plasma display. When it turns on it complains that the real-time clock has stopped and the CMOS configuration is invalid. Time to open it up and replace the CMOS battery!

Getting the hardware together

I relied heavily on a scanned copy of the Gridcase 1500 Disassembly/Reassembly instructions that were uploaded to the (now-defunct) "RuGrid Laptop" Yahoo group. The images in that document are a little low-resolution but hopefully the pictures in this post will help you out.

Also be aware that there are at least two different revisions of the Gridcase 1520 main board: one which has a soldered lithium battery and an MC146818AP RTC chip, and one which has a Dallas 1278A RTC with embedded lithium cell. This post is about the former type; if you have one of the latter then you're out of luck since the Dallas RTC module is difficult to remove and hard to source a replacement for.

Taking the hardware apart

You can now lift the main board out and access both sides to remove/replace the CMOS battery.

Replacing the battery

The CMOS battery is a 1/2 AA size 3.6V lithium. I found those with leads soldered to them quite expensive, so instead I got a regular 1/2 AA lithium and a cheap through-hole battery holder. This seemed like a really good idea until I reassembled everything and found the holder with battery was ~2mm too tall for the keyboard bezel and screen to close properly. I ended up having to sand down the bottom of the battery holder to make it fit :-(


Reassembly is the reverse of disassembly. Remember that you took it apart; you can put it back together again. By all means, do not use a hammer.

Main board pictures

Some bonus pictures of the main board: