HP 35

[manicminer]

Hi all,
I just got a very used HP 35 calculator on a swap meet.
It comes with the original Varta battery pack but with no power adapter.
I have no idea if the calculator is working. Is there any way I can test it? Can I buy a power adapter for it?
Thank you in advance

[jackrubin]

Lots of choices on eBay - used or new. Take a look at this USB charger - 323809756858 . I've bought a couple from the seller and am quite happy with them.

[AndiGer]

If you want to test before you buy a charger or rebuild the battery pack you can test the calculator from a normal DC converter or another DC power source that gives (3 * NiCad by 1.2 V = ) 3.6 V to 4.5 V. Polarity must be observed: Negative polarity to the upper pole. See this picture: https://www.hpmuseum.org/batts/battcls.jpg
Look for the two pins where the plug goes into. With no plug installed the two outer pins are connected by the brass sheet inside. I.e. use a DMM to check those pins are connected together. Otherwise the calculator will not work as it doesn't with the plug connected but wall plug not connected to the mains.
Good luck
Andi

[manicminer]

Hi
Thank you both for the quick reply.
In fact, I would like to test de device before spending on power charger + battery pack.
The screws on the back have a lot of corrosion and the calculator might be needing of repairs that I might not have the skills to make.

AndiGer, I don't quite understood the procedure about the connections. I'm sorry, but could you please explain it again?

Thank you in advance

[Didier Lachieze]

Here is a picture showing the battery contact polarity:



You can use it to connect a 3.6V to 4.5V power supply.

You may want to share pictures of the battery compartment of your HP-35 so we can see the level of corrosion.

[AndiGer]

2nd part of my post: see here - https://www.hpmuseum.org/batts/battery.htm
Part: Classics (HP-35, 45, 55, 65, 67, 80)

[manicminer]

Thank you so much for your replies.

Here are some photos.

1- Battery compartment



2- Corrosion on the contacts



3- The machine itself





4- I've found a battery compartment, and 3 AA Ni.MH batteries rated at 1.2V - 2500mAh
I can cut the power connector, and directly connect the wires to the terminals. Making sure I've got the polarity right, would this work?



Kind regards

[Harald]

(06-19-2019 08:49 PM)manicminer Wrote:  Thank you so much for your replies.

Here are some photos.

1- Battery compartment



2- Corrosion on the contacts



3- The machine itself





4- I've found a battery compartment, and 3 AA Ni.MH batteries rated at 1.2V - 2500mAh
I can cut the power connector, and directly connect the wires to the terminals. Making sure I've got the polarity right, would this work?



Kind regards

Yes, that would work. Avoid soldering the terminals of you can. It's not nice to have solder on the gold plated terminals.

From the pictures I would guess your calculator works. Good luck!

[AndiGer]

For test purposes you could try to grab power with two wires directly inside the compartment. So you don't have to cut the plug.
It's a version 2 with the raised dot on the 5 key. Maybe got the 2.02 bug.

[burkhard]

Looks pretty nice!
I'm betting it will work, but don't be surprised if the power switch needs a little wiggling. That is common can later be dealt with easily... So, if it doesn't seem like it turns on at first, don't lose hope :-)

[manicminer]

Hi all.
It didn't work. But I am also suspecting the battery pack that I've used to test also might be broken. I'll borrow a Multimeter and test it.

[Harald]

(06-21-2019 11:13 AM)manicminer Wrote:  Hi all.
It didn't work. But I am also suspecting the battery pack that I've used to test also might be broken. I'll borrow a Multimeter and test it.

Yes, measuring if you actually have the correct voltage at the terminals is a good idea. You could also measure if the calculator is drawing any current.

Keep posting your results and don't give up on the calculator. If all else fails, it might be a candidate for the multi emulator replacement board.

Cheers,
Harald

[manicminer]

Hi All
It lives!

I've test powered it with 3 AA cells, and a temporary direct connection to the terminals.

Now I must decide the next steps.

1- Try to find in Europe (or overseas depending on postage) a battery pack, a power / charger cable.

2- Leave it like this and display it for it's historical value

I would really like to use it. It's my first HP calculator ever.




Kind regards

[AndiGer]

Congratulations!
Now that it is alive and is a version 2 you can try if it has the 2.02 bug.
(2.02 ln e^x --> 2.02 it has not, 2 it has).

[Willy R. Kunz]

(07-11-2019 03:52 PM)manicminer Wrote:  Hi All
It lives!

I've test powered it with 3 AA cells, and a temporary direct connection to the terminals.

I would really like to use it. It's my first HP calculator ever.




Kind regards

Interesting picture you’re showing here. Obviously you were checking if your HP-35 has the very rare “Big Bug”, where 1 EEX CHS LN would result in -123.0258509. Too bad it doesn’t. Less than half a dozen HP-35s having the bug are known to exist.