HP 41 mains adapter/charger UK (82067B)

[n1msr]

Hi.

I am looking for a reliable way to check my 82067B UK mains adapter/chargers for my HP-41CX. Here's some detail:

I have two HP mains adapter/chargers for the UK. The part number is 82067B. I have one old rechargeable battery pack and I am trying to get this to power a 41CX. These items have worked previously, but at least 5 years ago. (I have ordered 4 x N alkaline batteries to check the calculator, but need advice on the mains adapter.)

I measured the voltage output from the rechargeable battery pack - it is 0.33V, i.e. way to low to power the 41CX. When I connect either of the mains adapters to the battery pack, I don't hear any "hum", which I think I should, but am not certain. Also, when I check the voltage at the calculator plug end (two-prong) of the mains adapter when connected to UK mains (~240V), I get a very low reading that look like "random" multimeter values. (I checked the fuses in the UK plugs and they are OK.)

Is there a reliable way to check these adapters without dismantling them?

Thank you,

Mark.

Is

[Frido Bohn]

Hi Mark,

I have an HP 82066B adapter which is the continental European variant of your device. It runs on 220V input and delivers nominally 8V / 3VA output. When measured with a voltmeter (input 227 V) and without any load it delivers 11.6V. Please observe that this is all about AC!
My HP 82066B has no fuses and is not meant to be disassembled by the standard customer. If something with the wiring of your device's transformer is defective a repair would not be easy. If it is about a cold solder joint at the output line it should be not too hard to fix that.

Cheers!
Frido

[AndiGer]

Hi Mark,

As Frido already mentioned - output is AC ...
DMM at DC settings measuring is as you described - low and random and you think the charger is defective.

Andi

[n1msr]

Frido & Andi,

Thank you both very much for your prompt and informative replies. I did not know that the OUTPUT is AC. I just checked both with the multimeter (on AC voltage setting this time!) and under no load it is around 12.5V, so both adapters seems to be working.

Is it usual for adapters for HP calcs to be AC at the output? So what happens in the HP-41 battery pack? I assume the voltage is changed to DC for battery charging?

I left the battery on charge outside the calculator - just conected to the mains charger (I assume this would work) but the battery output has not changed. Its less than 1V (D.C.).

Mark

[n1msr]

Change in Post Subject, but it leads on from my previous question...

It seems my rechargeable HP NiCd battery pack for the HP-41C is not working. I would like to use NiMH rechargeables that I charge outside the calculator - not using the HP charger, of course, but one suitable for NiMH batteries.

The alkaline N cells are rated at 1.5V, but all the rechargeable NiMH cells I come across online are quoted at 1.2V. Will four of these (totalling 4.8V in series) work OK?

(Interestingly, it seems NiCd rechargeables are no longer sold to individuals here (UK/Europe). They are restricted to use by professionals. So you have to be a "company". )

Anyway, I would be happy with NiMH batteries if I could be sure they will work OK with the 41.

Thanks,

Mark.

[AndiGer]

More on the battery pack HP 82120A here:
https://www.keesvandersanden.nl/calculat...82120a.php

The NiCad rating in that pack also is/was 1.2 V each. So why shouldn't NiMH N cells work inside the battery holder? AFAIK a friend here on the forum uses these since years.

Andi

[Hiwi]

Hi Mark,
the mains adapters have in most cases a fuse, that is a thermofuse, which can be blown. It interrupts the mains line and is mouted on the metal sheets of the transformer.

This doesn't have to be be right for every adapter, but I have seen many euro adapters with such a fuse.

Anyway your adapters are working.
The voltage is rated at 8V, with no load it is SQ(2) times higher, that is correct.

NiCd Cells in that size are no more available. If you take NiMh that would work, but the charging time for a full charge is about 2 days or more. (depends on capacity of the cells)

I made some tests with a professional batterycharger. I most cases the batteries were not fully charged.

That is because the charger circuit limits the current to 6mA. And NiMH cells don't like the charger characteristic for NiCd. At least this is not the best solution.

You can modify the charger unit, that it delivers 20mA or so.

But there are other solutions:

Diego has a nice battery replacement with LiIon/LiPo cell and a 5.xV regulator, or you can get
standard Lady NimH cells and charge them externally. They are available on TAS for low price including an usb charger. The chinese manufacturer rated them with 700mAh. But this is only a dream :-) I was only able to push about 400-500mA into these cells.

Ralf

[n1msr]

Ralf,

Thank you for your detailed reply. I have heard of the USB charged 41 battery packs made by Diego. I emailed him a month or so ago, but he had run out and said he would email me when he started a new batch. I heard about his 41 battery pack from one of the HHC Youtube videos (always worth a watch post-conference), and they seem to last "forever" compared to the original rechargeable pack.

I will try Diego again though, just in case he wants something to do :-)

My 41 "revival" is part of a renewed interest in some of my older HP calcs. I have Tony Nixon's upgraded CPUs in two HP-67s and an HP-65 that has been repaired (LED, card reader and CPU) by a friendly guy in Spain. Its great to see the dedication of specialists in reviving and sometimes enhancing these beautiful machines. They just don't make 'em like that any more. But all the members of this forum know that!

Regards,

Mark.

[n1msr]

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