HP 41C series battery issues

[Wes Loewer]

(06-20-2020 01:37 PM)Andres Wrote:  IIRC HP-41C includes a diode in the CPU board to prevent damage to circuits due to errors in battery polarity.

This reminds me of an incident that happened around 1986 or 87. I was a graduate student at Texas A&M and there was an hp dealer just off campus. My 41cx was behaving strangely so I brought it to the shop when there were a couple of guys from HP who were there for some promotional event. I showed it to them and mentioned that the coat I carried it in often generated static electricity when I put the coat on or off. One of the guys took the calculator and said "don't tell anybody I'm doing this" and proceeded to remove the batteries and put them back in with the polarity reversed. When I expressed my "concern" he assured me that it would be okay. He left them in for a short while and then reversed them again back to their correct polarity. Sure enough, when he turned the calculator on everything worked fine. He said that the 41's were susceptible to static and reversing the batteries cleared the problem.

I'm not recommending that anybody try this, but that's what happened. But now it makes me wonder: Since there is a diode, what good did reversing the polarity actually do?