hp classic calculator charger without battery pack

[zixingcheche]

Hi

Can I use the HP classic charger with the HP45 67 80 calculator without the battery?
(Only charger & calculator)
The Woodstock will be damaged by charger without battery.

Thanks

[mfleming]

35, 45 yes. 67 no. Your best source of information on which model can be powered without the battery present is the owners manual. You can find PDF copies at literature.hpcalc.org (along with all sorts of other great manuals)

[zixingcheche]

(01-07-2023 01:10 PM)mfleming Wrote:  35, 45 yes. 67 no. Your best source of information on which model can be powered without the battery present is the owners manual. You can find PDF copies at literature.hpcalc.org (along with all sorts of other great manuals)

thanks！I will check it.

[teenix]

The Classic chargers like 35, 45, 55, 65, 70, 80, (and 67?) have a logic voltage supply available as well as a charging current circuit for the battery. The 35, 45, and 70 owners manual says it is ok to run these on the charger without a battery installed. Why the other Classics don't, I'm not sure why as they are all much the same. Even if it is ok, then what condition is the battery charge circuitry and connections. (Corrosion etc).

For other models: 65, 67 21, 22, etc, the manual says it may cause damage to the calculator circuitry, and indeed it does. Sadly, some people have been stung by this.

Also, the calculator/charger components are quite old now and may not take too kindly to power spikes by plugging in a charger that is already connected to the mains for example, as happens quite often these days with modern phones etc. This warning also appears in the manuals.

All said and done, it is always wise not to run any of these calculator models from the charger at all, battery or no battery, and also charge the batteries outside the calculator.

cheers

Tony

[zixingcheche]

(01-08-2023 01:49 AM)teenix Wrote:  The Classic chargers like 35, 45, 55, 65, 70, 80, (and 67?) have a logic voltage supply available as well as a charging current circuit for the battery. The 35, 45, and 70 owners manual says it is ok to run these on the charger without a battery installed. Why the other Classics don't, I'm not sure why as they are all much the same. Even if it is ok, then what condition is the battery charge circuitry and connections. (Corrosion etc).

For other models: 65, 67 21, 22, etc, the manual says it may cause damage to the calculator circuitry, and indeed it does. Sadly, some people have been stung by this.

Also, the calculator/charger components are quite old now and may not take too kindly to power spikes by plugging in a charger that is already connected to the mains for example, as happens quite often these days with modern phones etc. This warning also appears in the manuals.

All said and done, it is always wise not to run any of these calculator models from the charger at all, battery or no battery, and also charge the batteries outside the calculator.

cheers

Tony

Thanks for your advice! to charge the batteries outside the calculator is more better.

[badaze]

Hello,

I have this HP 67 with a broken battery contact and it works without battery pack.

[AndiGer]

(01-08-2023 01:56 PM)badaze Wrote:  Hello,

I have this HP 67 with a broken battery contact and it works without battery pack.

What is often said ... as long you don‘t (try to) use the card reader ...

[badaze]

(01-08-2023 02:58 PM)AndiGer Wrote:  

(01-08-2023 01:56 PM)badaze Wrote:  Hello,

I have this HP 67 with a broken battery contact and it works without battery pack.

What is often said ... as long you don‘t (try to) use the card reader ...

Thanks.

[teenix]

(01-08-2023 01:56 PM)badaze Wrote:  Hello,

I have this HP 67 with a broken battery contact and it works without battery pack.

From page 312 of the HP-67 owners manual...

CAUTION
Operating the HP-67 from the ac line with the battery pack
removed may result in damage to your calculator.

A game of chance perhaps.

Assuming the charger components have not degraded over time, and it is supplying the correct power to the calculator, this is probably a warning about mains spikes and surges which will probably pass through the charger and into the calculator circuits and damage them. It might be enough that when a fridge or vaccum turns on or off, or next door is welding, or a lightning storm that a damaging spike could occur, of which the ACT chip seems most susceptible. Perhaps the battery in place helps to dampen these transients.

The other problem is that the charger is not designed to solely provide the current needed for the card reader let along both the calculator and reader, and this could also cause problems especially if the charger components are not up to spec anymore.

cheers

Tony

[Jeff_Birt]

(01-08-2023 10:34 PM)teenix Wrote:  Assuming the charger components have not degraded over time, and it is supplying the correct power to the calculator, this is probably a warning about mains spikes and surges which will probably pass through the charger and into the calculator circuits and damage them.

The warning is not related to any spikes or noise on the AC line.

The chargers/wall-warts are unregulated power supplies (a transformer, rectifier and filtering cap). There is no voltage regulation. A 6V adapter might output ~8V when not loaded. As you approach the rated current capability of the adapter you get closer to the rated voltage.

When you plug the adapter in the load of the battery pack helps loads the adapter and lowers the voltage applied to the rest of the system. With our example of a 6V adapter that outputs ~8V unloaded, the load of the battery back would drop it down to ~6V. Without the load of the battery pack too high a voltage is applied to the rest of the electronics.

If, IIF, you understand what voltage would be applied with the original adapter loaded by the battery pack, to the machine you can substitute a well-regulated adapter of the proper voltage. If you do this wrong though you chance blowing things up.

I did a video on this very subject recently. https://youtu.be/f2ShjK9uq9Y