My First Red LED Machine (HP 45)

Whoo Hoo! I finally have red LED's in my Collection!!!
S/N: 1350A10347

More images later. I have a field case, hard case and some literature too.


Looks good, I hope you also have batteries in that thing! You may already know, but you should never run it just on a/c. Many here even charge the batteries separate from the calculator. Because you have the a/c plugged in, I thought I would mention it.



Ouch! The previous owner, a college prof., said he ran it for years on the A/C alone. I guess I'm off to e-bay to find a battery pack. I did get what looks to be an external battery charger with the deal.

Thanks for the warning. It would be shame to fry my new baby.


Don't worry about running that particular calc off AC w/o a battery installed; it's completely safe. When you plug in the adapter, you completely bypass the battery circuit anyway, so the calc is going to see the same voltage regardless of whether or not a battery is installed. The models where that is a sure kiss of death are the Woodstocks and Stings, and to a lesser extent the Classic models with card readers.


It can certainly do no harm to only use the adapter/charger with a battery installed, but I do not believe there is any danger at all in powering the 45 (or the 35, 55, 70 or 80 models) directly from the AC adapter/charger with no battery in the calculator. The AC adapter/charger used on the 45 provides a regulated supply voltage to power the calculator. When the connector is plugged into the calculator, the calculator’s internals get connected directly to the regulated supply from the AC adapter/charger. The battery gets completely disconnected from the calculator's internal circuitry and is connected to the variable-voltage charging output of the AC adapter/charger. Page 48 of the HP-45 manual discussed what to do if your battery pack went bad, stating "Remember, you can use your HP-45 on AC power until the replacement battery pack arrives.”

This does not apply to the HP-65 or HP-67 which use the same charger, but (if I recall correctly) leave the card reader circuitry connected to the battery and the variable voltage charging supply, so if there is no battery that voltage jumps up to something like 17 Volts which could damage things.



Congratulations! I was likewise happy when I got the 45, it's a good calculator. Use it!


Enjoy! It's a sturdy scientific calc and has got everything you need to master a major physics lab course at university - at least in 1975 and as long as a mains outlet is within reach ;-)


Congratulations! Today I received a working HP-80. It's fun to play with a non-programmable vintage HP. Have fun with your HP-45.



Here are some more pictures of the 45 and accessories. There is a little corrosion on the battery contacts an a little dust and wear on the front but otherwise very nice. All can be viewed at: Photo Set

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