Changing battery in 42S



#19

Changed the batteries in my 42S last week. I did so as quickly as possible, but the memory was still reset. Is there a way to change the batteries in a 42S without loosing the memory? Just would like to know for the next time.

Thanks!


#20

If the old batteries are not exhausted, internal capacitors / capacitance will keep some charge and thus the contents of the calculator will be preserved for about one minute, which should be enough. It is important not to short the terminals when inserting the batteries.


#21

Quote:
It is important not to short the terminals when inserting the batteries.

Yes! Furthermore, this is likely to happen when one tries to replace them as quickly as possible.

http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/archv016.cgi?read=102675

#22

Quote:
If the old batteries are not exhausted, internal capacitors / capacitance will keep some charge and thus the contents of the calculator will be preserved for about one minute

Recently I needed three LR44/357 cells for a small UV light, and had none in the house. I had two Pioneers, a 17b and a 22s. Since I thought I could more afford to lose the Solver routines in the 22s than the 17b, the former became the donor.

Much to my surprise, even after being out of the calculator several minutes, when put back in the 22s had retained all memory.

#23

The HP 42S has been my main work calculator for 14 years, and I've replaced the batteries at least three times. I've never has a "memory lost" condition during battery change occur on the 42S, or any other of my six Pioneers and four (old) Voyagers.

I have the three new cells lined up, ready to go. Then I slap the 42S down in hand to make the old cells slip out, then I carefully insert the new ones, avoiding shorting of the battery clips.


#24

Quote:
I have the three new cells lined up, ready to go. Then I slap the 42S down in hand to make the old cells slip out, then I carefully insert the new ones, avoiding shorting of the battery clips.

I routinely use stacks of three cells bound with a single wrap
of thin (eg: 2mil) tape, which incidentally works better in a
42s/17b than a voyager due to more generous access to the battery
well.

In any case the unified stack prevents inter-cell shorting and
the tape excess can be folded over the edge of the negative-most
cell to prevent accidental shorting to its case when the stack
is inserted.

[s/14s/42s]


Edited: 4 Nov 2011, 5:28 p.m.

#25

Hi Keith,

The standby current of the HP 42S when power off is around 9uA by my measurement.

It's quite large to hold the memory without batteries i.e. the internal solid tantalum capacitor of 100uF lose its charge within several seconds.

It's because the internal clock oscillator is active and keeping oscillation (for the un-implemented real time clock functions) in that state.

On the other hands, in the sleep mode, it'll goes down to less than 100nA at nominal temperature.

In this case it will hold the memory for a minute or more.

So it's recommended to put the 42S into the sleep mode by pressing

[EXIT], [+] and [XEQ]

simultaneously before battery replacement.

The other option is to connect an external power supply of +3.6~5V with series protection resistor of 1K Ohm before battery removal.

Good luck

Lyuka


#26

I did a light search and didn’t find a thread about, sorry if it has been discussed before.
Talking about current draw, has someone measured the Pioneer series?, from my experience, time between battery change, 20S batteries seems to last forever, 22S and 32SII I will say it’s OK, 4-5 years even if my usual choice is the 32SII, but 27S and 42S (upgraded to 32K memory) are around 1-1.5 years. Any measurements that can back up my experience?


#27

Hi Julian,

Please take a look at,

HP 27S : Irun ~= 6~11mA, Iidle ~= 340uA, Istandby ~= 8.2uA, Isleep ~= 170nA

HP 32sII : Irun ~= 1.0mA, Iidle ~= 120uA, Istandby <= 100nA

HP 42S : Irun ~= 3.3mA, Iidle ~= 380uA, Istandby ~= 8.9uA, Isleep <= 100 nA

Regards,

Lyuka

Edit to use 'u' instead of using Greek mu character.


Edited: 5 Nov 2011, 3:43 a.m. after one or more responses were posted


#28

How can I enter sleep mode on my HP 32sII?

/Sören


#29

Since the 32sII has no real time clock nor crystal oscillator,

there is no need to keep partial circuit active when power-off.

In other words, it's already in sleep mode with quiescent current of as low as 100nA.

Lyuka


#30

Quote:
HP 27S : Irun ~= 6~11mA, Iidle ~= 340uA, Istandby ~= 8.2uA, Isleep ~= 170nA

How do you put a 27S into sleep mode?


#31

Just same as 42s.
Press [ON] [+] [1/x] simultaneously.

Lyuka


#32

Thanks!

BTW you wrote:


Quote:
[EXIT], [+] and [XEQ]

for the 42s, it should be [ON] not [EXIT], correct?


#33

Hi Katie,

If you mean [ON] as the key that activate the calculator, either way will do.

Pressing that key combination will bring the 42s to the sleep mode regardless of its ON/OFF state.

Regards,

Lyuka

#34

Where is this documented? I must not be looking in the right place.

#35

Pressing that combination [ON/EXIT][+][1/x] or [ON/EXIT][+][XEQ] on my 42S does not do anything while it is in "ON" state, while it is in "OFF" state no visible change either it remains off.
Edit:[EXIT][+][XEQ] works only when the unit is off. When turned on following this key squence for deep sleep, gives Machine Reset message.


Edited: 6 Nov 2011, 5:40 p.m.


#36

Hi,

Just try the key sequence below,

Press and hold [EXIT], press and hold [XEQ], press [+] and release, release [XEQ], release [EXIT].

Key sequence (timing chart) to put an HP 42S into sleep mode.

[EXIT] ~~~~____________________~~~~
[XEQ] ~~~~~~~~____________~~~~~~~~
[ + ] ~~~~~~~~~~~~____~~~~~~~~~~~~

You'll see "Machine Reset" message at power on after sleep mode.

Lyuka


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