brand@janus.uucp (Graham Brand) (03/01/88)
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@janus.berkeley.edu)
stevewa@upvax.UUCP (Steve Ward) (03/02/88)
In article <23151@ucbvax.BERKELEY.EDU> brand@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@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@upvax.UUCP !tektronix!upvax!stevewa
wtm@neoucom.UUCP (Bill Mayhew) (03/02/88)
The author didn't say exactly how the clock stopped on the PC6300. If the clock seems to freeze at a certain time without going to zeros in all registers, the problem is most likely that the nicad battery is not supplying sufficient voltage for proper operation. In most cases the battery cuases problems when the PC6300 is used less than a few hours a day. One solution is to compute more. Another fix suggested by an AT&T service rep is to just leave the machine on overnight every now and then to make sure the battery gets a full charge. In extreme cases, it is best to replace the battery. --Bill