Strange Real Time Clock fault - any hardware experts out there?

[Steve Ward]

In article <23151 at ucbvax.BERKELEY.EDU> brand at janus.UUCP (Graham Brand) writes:
>I have a PC6300 with 640k RAM, 20MB HD and DOS 2.11 which has
>been working fine for the past two years. Recently, the real time clock
>died. In looking at the circuit, I thought that the simplest solution
>would be to replace the clock chip. As the chip was soldered directly to
>the motherboard, while replacing it, I put in a socket. After replacing
>the chip everything worked fine for about a day. Then the clock stopped
>again. I replaced that chip with another and that worked fine - but for
>only a few hours!
>-Graham Brand		(..!ucbvax!janus.berkeley.edu!brand)
>			(brand at janus.berkeley.edu) 

Sounds to me you have a dead battery for the clock.  The average lifespan
of these batteries is about 2 years, and when they start to get old, they
exhibit the sort of behavior you're describing. (I'm assuming, of course, 
that your machine kept track of the time even when it is turned off)
If the battery is indeed the problem it should be a simple fix...most of
the batteries are simply stuck to the side of the chassis somewhere, with
a wire leading down to the motherboard (some designs, esp. in add-on clock
units use a large, flat "watch battery" mounted right on the board in a 
plastic holder.)  Just unplug the computer, pull the wire connector off the
pins on the motherboard (or slide/pop the old watch battery out the holder)
(in either case make sure you note cable position, which side up, etc.), then
pop in the new battery.

Typical cost is under $25...if it's an unusual type, you might have to order
it from the manufacturer.

After you have the new battery installed, you'll have to reset the clock,
and run SETUP to re-configure your machine (if you have system configuration
info in CMOS RAM).  I'd also reccomend leaving the machine on for a few hours
(some systems use NiCad batteries, and they have to be recharged after storage)
AT&T may have a kit you can buy containing instructions specific for your 
machine.

Good Luck!

Steve Ward
stevewa at upvax.UUCP
!tektronix!upvax!stevewa