in Electronics, Retro computing

My first Real-Time Clock chip mod

Recently I got GA-586HX Rev 1.53 motherboard. Wanted to test it with Pentium 166 CPU I had. Noticed that in Bios I can set whatever I want but only the clock/date is saved and nothing else, also the clock was not ticking.

It had Benchmark bq3287mt Real Time Clock module. Luckily, on this motherboard it was in a socket, so that solves a lot of trouble.

GA-586HX Rev 1.53 with Benchmark bq3287mt Real-Time Clock module
Benchmark bq3287mt Real-Time Clock module taken out of the socket

So I had an option to order a new one or try to make an RTC module mod and add an external cell battery. I have never done such a mod so of course, I decided to try 🙂

Mostly everyone on the internet suggests to Dremel out the side of the module to access power pins and solder their wires from the coin battery holder.

I decided to go slightly another way.

I took an electric drill with a small disk with sandpaper attached to it. Then I fastened the RTC module in a vice and started sanding off from the top hoping to get to the battery and remove it.

Soon I started to see battery.

Sanding off the top of the Benchmark bq3287mt Real-Time Clock module

After some more time…

Sanding off the top of the Benchmark bq3287mt Real-Time Clock module

The battery was not going out, so I have decided to sand more and it was a bit too much – I have damaged crystal on pins 2 and 3. Oh well, all was left it to try to sand out all the epoxy until IC will be accessible and see if I can fix it.

After some time, when there was little epoxy left, it started to crack and I could easily remove it with a sharp knife.

Benchmark bq3287mt Real-Time Clock module with epoxy removed

Then I cleaned everything out and in my used electronic components box found one crystal ( I have no idea where it was from and what model it was, but it just looked similar so I have decided to try ), and a coin battery holder.

Soldered crystal to IC pins 2 and 3 and then glued and soldered battery holder to IC pins 16 and 20. And what do you know, it worked!!! The clock started ticking and all settings I hame made were stored in CMOS.

Benchmark bq3287mt Real-Time Clock with new crystal and battery.
Benchmark bq3287mt Real-Time Clock with new crystal and battery.
Benchmark bq3287mt Real-Time Clock with new crystal and battery.
The clock is ticking with modified bq3287mt Real Time Clock

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