Storing calculator



#12

Could anything go wrong if a pioneer series calculator is put away for 2 years, say, without batteries in it?
Thanks in advance.


#13

I have an HP41CV that was brought back to fully-operative life after not less than 9 years stored in a box, completely disassembled. Keyboard assy and back case separated, mainboard left aside loosely... and it is alive and well after a bit of cleaning and building. It may not happen to everyone, so, please, do not try it.

The pioneer series? Well, they will not allow easy opening, and they also do not have a mainboard that can be placed apart. My HP42S was also left aside (batteries inside) for about four years. I had only to change the batteries, original se, for a fresh set.

If it helps...


#14

Most likely the reason why you had to take your 41CV apart was that it's several boards inside joined by not particularly brilliant connectors.
Bad contacts are common in the 41 machines. Had you been using the machine rather than letting it sit in the box, you'd still have had to clean the
contacts sometime. The Pioneer machines don't generally suffer from contact problems, so there's no reason to worry if you store one. Just take out the batteries so they don't leak inside the machine

#15

Perhaps some components could reverse polarity if left unused for years.

I suggest you turn on all your HP calculators for a few minutes at least once every three or four months. That's what I do, and some other collectors I know do the same, seems to help keep the machines healthy.


#16

Perhaps somebody could explain the physics behind this 'polarity reversal' and which components are affected. I understand why a series string of secondary cells (like the NiCd pack in an HP calculator) can
suffer from polarity reversal of the weakest cell after many charger/discharge cycles, but I've never heard of any other component being affected.
The problems with old HP calculators seem to be mechanical problems (contacts, rollers) that will go bad whether you use the machine or not, electrolytic capacitors (which will last longer if they are used, but which are easy to replace) and semiconductor (IC) failure, which is more likely to occur if the machine is used, but which is hard to repair (the chips are almost all custom).


#17

Electrolytic capacitors might be damaged on a reversal.
Old electrolytics used to have a problem of going "dry" as
well, but I haven't seen this in modern components much.

I've had a number of calculators in storage for many years
and they work just fine. (hp-41's, hp-29c, hp-15c, hp-16c)

I was even foolish enough to leave the batteries in the
hp-15c and hp-16c, with no problems at all. In fact, I
had the original batteries in one of them for about 15 years
I think before they finally gave up.

Cheers.


#18

Plenty of components will be damaged if the supply polarity is reversed. Electrolytic capacitors, most chips, even some LEDs will be ruined.
That is not the same thing as saying that the 'polarity' will reverse if the machine is stored without batteries installed. That's the part I can't understand.
The polarity of what will reverse, and what is the physics behind it?

#19

I have posted a similar question sometime ago on storage of calculator. I was told by many of the folks here that I should have all the batteries removed before having them permanently stored!

Since then I have probably hundred calculators (some brand new and some used, includes Classic, Woodstock, Spice, Voyager, Champion, 41C’s and Pioneer etc.) sealed in airtight bag with batteries removed for my collection. I sure hope I don’t have to cut open all the bags now to put in the battery – I was thinking of doing that probably thirty years from now :-)

#20

I’m an Electrical Engineer and I understand what do you mean by trying to figure it out. Physically, there is no way to reverse the polarity of a bipolar junction, unless you build it up reversed. Diodes and all sort of semicondutive components can become short-circuited, open OR change their semiconductive characteristics. But I have never seen one that have switched from A-K to K-A. It happens that some other, passive components change their operative parameters, resulting in an abnormal behavior. Sometimes, it is referred to as a 'polarity reversal' condition. I myself got used to the term, and understand that it refers to some sort of abnormalities. Batteries also change their polarities themselves, and I have seen some LR44 with about -.5 V, but they cannot be any source of current.

If you who read also deal with electronic components too, sorry for the mambo-jambo.

#21

I could not agree more! You´re completely right about components, specially electrolytic capacitors that exist in some older models.

My 41CV 'Phoenix' Model (from the ashes) has two of these, and I was somewhat worried about them. This machine was given to me as junk, and I stored it for future use. Voillá! It´s alive!

Thanks for the tip.


#22

I recently rejuvenated an HP35 that had not been turned on for probably 20 years. It had been stored (that's a fancy term for lying around in a drawer somewhere!) without the battery pack installed. I made a new battery pack with the recommended Panasonic cell phone battery (see elsewhere in the MoHPC), and it seems to charge up OK with my old HP power pack. For the first few minutes of its new life, the calculator displayed all the decimal points (a signal of low power, I think), but after that, except that the battery connections aren't as tight as you might like (I made a pretty ad hoc set of connectors), it works fine - either on the battery or the power pack. (The decimal point key is a little flakey after 38 years, but so are we when we get that old.)

I, too, was a bit worried that any electrolytics might have gone south in all those years, but that doesn't seem to be the case. As far as I can imagine, except for batteries, there is nothing else in there that should slowly fail with old age. (My Heathkit (another sad story) digital clock, from 1966, is still working fine, with its neon segment displays. Solid state equipment really does last almost forever if not mistreated.)


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