CMT 64Kb RAM module for HP-71b question

[rprosperi]

(09-08-2021 01:23 AM)polbit Wrote:  I have recently received one of these, and it has this silver rectangle pouch(?) that fits mostly into the module as it is inserted into 71. Since I can’t find any instructions, etc. can someone let me know what that is, why is is different from the 32k modules? Thanks!

That's a battery. The 32K modules could preserve contents for a few seconds, e.g. while swapping ports; the board/component design had enough capacitance (maybe not the right term here) to maintain the RAM contents. But the 64K+ modules could not retain their contents, so CMT added this very small lithium battery, to similarly retain RAM contents for short periods.

Your battery is almost certainly dead, and unfortunately, no one has been able to locate a supplier for replacement batteries. The module itself will still work fine, even with a dead battery, but if you remove it from a 71B, it will instantly lose contents.

Yeah, he beat me...