dcoster@phoenix.Princeton.EDU (David Peter Coster) (02/20/88)
A while ago I posted the following message:
On three occasions I have had a message saying that the memory on
my HP28C has been lost. The first time it happened, I had a
fairly long program to draw the Mandelbrot set in the memory.
Since then I have been loathe to put in any long programs since
they could disappear at any stage (or so it would seem). Has this
happened to anybody else? How can I cure my calculator of this
annoying habit? (The batteries should still be good, and I have
had no low battery annunciator).
I received no replies, but at the same time the calculator stopped
misbehaving. In the last few days however, I have had the memory lost
message three times. It is rather frustrating not knowing whether the
results of a calculation are going to be there when you next switch
the calculator on. Does anybody have any suggestions? Has this
happened to anybody else?
If it needs to be repaired, is there any way of upgrading it at the
same time (I don't intend fixing it myself as it is still under
warranty - at least I think so, I'll have to check).
David Coster
dcoster@phoenix.princeton.edu
dcoster%ppc.mfenet@anlvms.bitnet
dcoster%ppc.mfenet@nmfecc.arpabillw@hpcvra.HP.COM (Bill Wickes) (02/25/88)
The memory lost problem has plagued the 28C throughout its product life. The problem appears to arise from corrosion (microscopic, not great dripping rust blobs) of the battery contacts. All 28's are now shipped with Kodak batteries; their gold contacts seem to substantially alleviate the problem. Other things you can try for preventative medicine: *Clean the battery contacts every week or so with a pencil eraser. *Insert a thin wedge of foam tape along one corner of the battery compartment to keep the batteries from rattling in the case. If these measures don't improve matters, you may simply have a bad unit--send it in for warranty service. Also, as for any other CMOS calculator, be careful of static electricity. The 28 can survive shocks on the order of 15KV, but it's possible to exceed this in particularly dry conditions