Dallas Semiconductor DS1387 Module Rework/Battery Replacement

Inspired by my recent success in reworking several DS1287 real time clock modules, I got brave and turned to the problem of reworking the DS1387. The DS1387 is also a real time clock module, but it has extra NVRAM. Unfortunately, Dallas Semiconductor discontinued production of the DS1387. All the DS1387s that will ever exist have been made, and I know of no compatible part. In other words, I don't have as much room to make a mistake when opening the module, disconnecting the internal battery and connecting a new battery.

(It should be noted that the Interstate Battery System of America claims to carry a DS1387 replacement to this very day. I haven't ever tried ordering one and don't know what they're selling. Perhaps such a part does exist, although I have never been able to find one.)

Meanwhile, Dallas/Maxim's own CEO once said that his company would never discontinue a part, because their inconvenience in continuing production would not outweigh the benfits of satisfying their customers needs. I guess that didn't quite take effect before the DS1387 was shown the door. I can't find the exact quote on their website, and it's probably been removed. Oh well...if they were still making the DS1387, I wouldn't be having this much fun and you wouldn't be reading this web page.

Well, let's get started.

The first thing you'll notice is that the DS1387 module has more pins on it. Where the work area on the DS1287 is fairly wide open with missing pins, the DS1387 has more pins to occupy the normally empty spots on a 1287. However, the basic concept--and even the pin numbers--are the same between the two parts. You basically need to cut open the module at missing pins 16 and 20.

When opening a DS1387 I found the battery "wiring" was much closer to the surface of the potting compound. I didn't have to dig nearly as deeply to get inside and disconnect the battery. On the other hand, disconnecting the negative battery lead was harder than with the 1287, as I didn't have as much leverage on it from the sides. I used a combination of side cutters and needle nose pliers with serrated jaws to cut into the module. This has the advantage of cutting a groove into the top of the module that you can lay the battery leads in. That will help to protect them from being snagged by anything in your computer (such as expansion cards) that might be close to the module. Nothing will irritate you faster than ripping a lead from your freshly reworked module. Trust me, I know.

I'll skip the part where the module jumped out of my hands and sank its vicious pins into my skin. But that was annoying too, in case you're keeping score.

Note: When you get the contacts for the battery exposed, be sure to punch through at least one of them. Bad things may happen if the internal battery is somehow still connected. If you're not sure, put the module back into the computer after letting it rest for a few minutes after you've disconnected the battery. If you get clock or configuration errors upon reinserting the module and powering up, you have surely disconnected the battery.

Once I had the module open, I started attaching the battery holder to it. The following pictures show the process.

DS1387 with newly attached wires...

I used the vice because it makes for an easy way to take my temper out on the IC should things go wrong is all I have to hold parts being soldered. In the picture above, I've only soldered the leads to the module.

What the leads look like when glued down...

Now the leads have been glued down to the top of the module. I also glued over the solder points when they'd cooled enough to be stable. Every little bit of reinforcement you can apply will help.

Module side showing the glued-over rework...

Here you can see the glue on the side. In addition to providing strength and protection for the soldered on battery leads, the glue also covers up what a terrible job of soldering I did. (Don't kid yourself...I'm no solder artist, even after much practice.)

If you look carefully you can see that this workbench is used for a good many other tasks. Most of these tasks are related to woodworking or automotive projects.

The battery holder...

Here's a picture that shows the attached battery holder, which hasn't been seen until now. Again, please forgive the less than perfect-for-electronics-work workbench.

DS1387 back home in the computer...

Now the module is back in the computer where it belongs. The computer in this case is a PS/2 Model 53SLC2.

Battery Holder

I wasn't too sure where I should put the battery holder. Its leads were not long enough to put the batteries far away from the planar (system) board. I finally settled on wrapping it up in tape very thoroughly. The wires to the DS1387 run under the edge of the riser card, just past its own connector on the planar. They are just long enough to fit well, with some slack.


Years later, when I've forgotten all about having done this, I'll be able to pop the cover on this system and be reminded of those days...

I hope the tape will hold up well to any potential battery leakage. I couldn't seem to get ahold of any heat shrink tubing for this project.

The final view...

Here's the final picture of the finished product as viewed from above the computer. Good luck. If you rework a DS1387 or similar module, I'd love to hear about it.

What's Next?

Figuring out how to rework the Dallas module that's used in my Compaq Deskpro 386/33 computer. It's another different type of module and is longer than both the 1287/1387 parts. It too is discontinued.

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Copyright ©2007 William R. Walsh. All Rights Reserved. Permission is granted to reproduce this work in its entirety with all copyright notices intact. No advertising is to be displayed with this material if you reproduce it. No fee may be charged for access to this information, other than to cover any duplicating, media, or connect-time costs. Portions of this work may be used for other projects, provided credit is given for the portions of this work that you use and that such works are for non-profit distribution or information purposes. Ask me FIRST for permission to use this material in for-profit or commercial projects of any sort.