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

[EdFab]

On the HP 41CX on the right side, looking at the side, there is a slot. On my calculator, it's empty. What's supposed to go in there? Is there a cover for it?

[Paul Dale]

(09-06-2014 11:57 PM)EdFab Wrote:  On the HP 41CX on the right side, looking at the side, there is a slot. On my calculator, it's empty. What's supposed to go in there? Is there a cover for it?

AC power adapter. Yes there is a cover.


- Pauli

[Namir]

The first HP-41C calculators came with a rechargeable battery pack. You insert the A/C supply in the side port to charge the battery pack while using the calculators. Later on, HP switched to a battery holder that uses the N alkaline batteries. So the side charger port became the HP-41C version of the human appendix--useless!

Namir

[Joe Horn]

(09-06-2014 11:57 PM)EdFab Wrote:  On the HP 41CX on the right side, looking at the side, there is a slot. On my calculator, it's empty. What's supposed to go in there?

If you look closely in that port on your 41CX, there are two tiny holes in it that seem to serve no purpose. They are artifacts from the original design for the 41C, which had two spring-loaded gold-plated ball bearings there, which provided an alternate power supply path.



The 41C was made with those contacts for only a little while, because HP soon decided not to produce a matching power supply, and stopped including those ball bearings and springs in all 41's.

Namir: Are you sure that the original 41's came with a rechargeable battery pack? I seem to remember that every 41 came with the standard N-cell holder, and that the NiCad pack was an optional accessory.

[Sylvain Cote]

(09-07-2014 02:09 AM)Joe Horn Wrote:  Namir: Are you sure that the original 41's came with a rechargeable battery pack? I seem to remember that every 41 came with the standard N-cell holder, and that the NiCad pack was an optional accessory.

Your recollection is the same as mine Joe.
To my knowledge, all HP-41 ever produced were shipped with the N-cell holder.
Here a picture with the N-cell holder, battery pack and the charger.

Sylvain

[brouhaha]

(09-07-2014 12:38 AM)Namir Wrote:  The first HP-41C calculators came with a rechargeable battery pack.

Actually the first ones sold came with the N-cell holder, and had spring-loaded contacts in that side hole for a power adapter that never shipped.

It wasn't until later that the 82120A rechargeable battery pack was introduced. Fortunately (or perhaps through good planning) the hole was suitable for the 82059 and related chargers, which had been used for some earlier HP calculators, such as the 97 and 19C.

[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

[Didier Lachieze]

(09-07-2014 03:40 AM)Geoff Quickfall Wrote:  So in a nutshell, no direct AC power adapter ever was designed for the ball contacts.

There was one, but it was made by CT ( Corvallis Team) and not by HP.
More details here: 41C external power options?

[Geoff Quickfall]

I should have finished the sentence...

by HP.

:-)

[Jim Horn]

Actually, the homebrew cable using a modified TV power cord and an external 6 volt lantern cell was popular among some of the hard core '41 users due to the terrible effect the card reader had on the expensive N cell alkaline batteries. Those batteries cost about US$1.50 each back then (1979 - or over US$6 in today's money) but the over 1 ampere load placed by the card reader motor caused them to fail in card reader use once 10% of their capacity had been used (i.e. they still had 90% of their charge left). For anyone doing heavy '41 coding with magnetic card use (such as at club meetings making copies of a popular program for others), this was a real benefit.

Of course, the use of NiCd cells and later, HP's own NiCd battery pack, reduced the need for such kludges. But such is the way of progres...