The usual reason for these errors is a flat CMOS battery. In most machines this problem is easily rectified, simply requiring an over-the-counter 3 to 6v battery replacement on the motherboard. However the process is not always quite so hassle-free. Along with the real time clock this chip also holds the CMOS battery, all entombed together in a compact plugin unit. Rather neat perhaps, until the battery goes flat in which case the whole chip needs to be replaced! That is assuming you can get the part in the first place.

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Many other computers from the 90s used them as well. Throughout their lifetime, they do keep good time. Their lifetime is also quite long. Modules that are well over the stated lifetime of ten years may continue to keep time for another five years or so. The only serious drawback is the battery inside the module does eventually fail. When it runs down, you are left with the task of finding a new module and then justifying the purchase price against the actual value of the computer itself.

Fortunately, Peter Wendt of MCA Mafia fame has come up with an excellent page describing the subject of breaking open Dallas clock modules and how to connect them to external power sources. Go to his page now and read up on the subject. In fact, go print a copy of it right now. The suggested implement to open these modules is a Dremel tool. My Dremel tool--while a nice piece of equipment--spins at a minimum of 5, RPM and was all too happy to open not only the potting compound, but also the IC and in some cases, even the battery.

You will remember that I said something about a judicious application of violence on the Model 25 batteries page In any case, I turned to hand tools I started with a sharp knife to make the initial cuts and followed them up with by running the jaws of a needle nose pliers into the cuts.

For the second module I reworked, I did all of the work using a moderately sized side cutters. Whatever you do, handle the pins on the module carefully. If you fix the bent pins too many times, they will break off.

When you get past the potting compound and into the terminals, clear away just enough potting resin to catch the negative battery terminal heading up to the top of the package. You want to be sure the battery is disconnected, so double-check with a voltmeter.

It could start a fire, explode or just make a smelly mess. Soldering was the next big thing. In the event of a battery failure, the holder can be placed away from the sensitive planar or other circuitry. To give the newly reworked module some more strength, I used hot glue to secure the battery leads and holder inside the system unit. This picture shows the second module I reworked in a Model Be sure not to use rechargeable batteries.

There exists no modern day replacement for these, so re-energizing them is the only option.


DS12887 - DS12887 Real Time Clock Datasheet

Now the battery is dead, configuration is lost after relatively short time again and you get error-codes constantly. A really new, fresh and unused chip is hard to get. Even its successor DS is pretty hard to get and darn expensive. At that point you wish you could add an external battery.





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