What is the side slot on the HP 41CX for?

[Geoff Quickfall]

Okay, I am going to wade in here!

There was never a power supply direct to the HP 41c like the previous family versions. There was however, a power supply for anyone that bought the rechargeable power pack. It used the hole for a direct contact to the rechargeable pack.

The twin plated balls were designed to take an adapter (wall wart) that was never designed. In fact, there is a journal note, and I have reproduced it in house where a six volt lantern battery was wired through a tv household 120 volt plug to a narrow two pronged plug to the back of an old TV set. This narrow plug could be shaved to produce a contact set face at 90 degrees to the contact, making contact to the brass plated balls. In this way an hp 41c could be powered externally by a lantern battery.

So in a nutshell, no direct AC power adapter ever was designed for the ball contacts ( I forgot to add the following to the sentence) by HP! Later version of the pcb (PCA) cv an CX contained the contacts and construction for the balls but never had the balls installed. The halfnut even removed the contact traces on the PCB (PCA).

Again the only wall wart (adapter) for the 41 created by HP connected directly to the accessory known as the rechargeable battery pack and bypassed the ball contacts by HP.

The reason was that the n cells could power the thing for a year not over night like a 67 so who would need an external adapter, unless of courSe you had the rechargeable power pack.

Geoff