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

[Graham Brand]

I posted a request for help with this problem some time
ago but received very few responses. I now have a bit more information
which might be useful and, therefore, am reposting this now.

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!

As the unit is out of warranty, it will probably cost a lot to
send it to the ATT dealer so I would like to exhaust all possibilities 
first. Has anyone out there experienced this problem or can suggest a
solution?

Cheers,
-Graham Brand		(..!ucbvax!janus.berkeley.edu!brand)
			(brand at janus.berkeley.edu)