Dallas DS1287 battery replacement

[[email protected]]

Hi,

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.

Martin.

 

[Lostgallifreyan]

Hi,

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.

Martin.

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.

 

[Bill Janssen]

Hi,

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.

Martin.

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.

Good luck
Bill K7NOM

 

[[email protected]]

Hi,

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.

Martin.

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.

I think this marketing idea deserves a price!

Martin.

 

[[email protected]]

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.

I think this marketing idea deserves a price!

Martin.

There is no reason to assume that I was the first to dig into a
DS21287. Indeed, I just found this report which comes with pictures:

<http://perso.wanadoo.fr/dsavel/ds1287e.htm>

Martin.