after fifteen years of use, an old PC of mine has failed because the battery of the Dallas DS1287 gave up. This unbelievable epoxy-encapsulated circuit combines a real-time crystal clock and calendar, some non-volatile RAM for the system configuration, and a Li battery.
Has anyone ever chipped away at the epoxy encapsulation in order to locate the battery?
I am hesitant to throw away a clock crystal and CMOS circuitry merely because a battery has reached the end of its life. And the replacement DS12887 (good for another 10 to 15 years) sells for about USD15.
" snipped-for-privacy@freenet.de" wrote in news: snipped-for-privacy@y43g2000cwc.googlegroups.com:
Could you be sure that your chipped epoxy and battery replacement would be maintenance free for 15 years? :) The new unit sounds like good economy to me.
Yes I have done that for a SUN computer non volatile rom (NVROM). There is some instructions on how to do that on one of the SUN web pages (but not the Sun computer site). The chip is also known as a Sun IDPROM.
Thanks for the comments. I have now reverse-engineered a DS1287, using a rotary engraving tool and a soldering iron. This is how they were made:
Take a Dallas DS1285 chip in a standard plastic DIL-24 package, but with pins 2,3,16,20,21,22 bent upward (and slightly inward) instead of downward. Also take an unlabelled 32.768 kHz crystal in a TC-26 package (case dia 2mm, length 6mm), wind the wires into tiny loops, slip the loops over DIL-24 pins 2 and 3, trim the extra length of wire, and solder to the pins. Next take a Panasonic BR1225 Li battery (12.5mm dia, 2.5mm thick) with custom-made metal strips bonded to its sides such that elongated holes at the end of the strips slip readily over DIL-24 pins 16 (minus) and 20 (plus), and solder to the pins. Make sure that no space is left between the DS1285 and crystal or battery, and never mind that DIL-24 pins 21 and 22 are left unconnected. Obtain a black thermoplastic potting case that accomodates the circuit without taking much extra space, and also bonds with the potting resin. Use intransparently colored epoxy resin for potting. And finally, when cured, label your circuit Dallas DS1287.
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