HP 45 AC Adapter Question

[Eddie W. Shore]

Can the HP 45 calculator (from 1974) be operated with only the AC adapter (no battery pack)? Is it also worth $150?

Thanks in advance.

Eddie

[teenix]

(01-07-2022 01:53 AM)Eddie W. Shore Wrote:  Can the HP 45 calculator (from 1974) be operated with only the AC adapter (no battery pack)? Is it also worth $150?

Thanks in advance.

Eddie

The charger has two separate power supplies built in. One for charging the battery and one for powering the logic circuit while the battery is charging.

While the battery is charging, it is disconnected from the calculator, so while the calculator is turned on during charge, it is supplied only by the charger.

The charger supply for the calculator is a constant voltage design, so it should work ok. If the zener diode has failed however, you might risk calculator damage.

In that case, it would seem yes you can but I would put a load on the charger logic output and measure the output voltage first, just to make sure.

100mA thereabouts @ 3.75V is about 47 ohm 1W resistor.

cheers

Tony

[Eddie W. Shore]

Since the seller doesn't have a battery pack, and it is a sale at an auction site (not the auction site in case you are wondering), I think I may pass on purchasing it. Thank you once again,

Eddie

[Eddie W. Shore]

I finally purchased an HP 45 today. And yes, the AC can run without the battery pack. Glad to have one more from the early 1970s in the collection.

[Paul Dale]

Generally yes. If the AC adaptor is broken, then no but this seems uncommon.

Pauli

[Dreato]

to answer the original question, yes. no.