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Seeking advice from expert HP collectors
Message #1 Posted by John Smith on 22 May 2002, 11:45 a.m.

Hi, everybody

I'm seeking advice from some of the very knowledgeable HP collectors in this list, as I'm fully confident you will be kind enough to offer me very good guidelines.

The question is: I've got a number of HP calculators from the Voyager series (HP-11C, etc), and all of them use three small button cells. Now, as I can't use them all regularly, most of them have spent a number of years carefully stored in a drawer, with their batteries in place.

Now, though it has never happened to me, I'm aware that this is a very dangerous policy, because of battery leakage potentially ruining the machines, though I've never ever seen this happen in a Voyager series model, on the contrary, their batteries seem to last for decades on end.

Anyway, fearing leakages I decided to take out all the batteries from them and return them to their storage place, but after thinking about it for a while, I'm not so sure, i.e: could it also be bad policy to keep the calculators without batteries indefinitely, for many years ? Perhaps there's some internal electronics which would resent not being powered for a very long time ? I've heard something about 'dry capacitors' or the like, and I wonder if the lack of 'juice' could be as damaging as a potential battery leakage.

Just for example, an analogy from photography: should you keep a large, complex zoom lens without using it at all for many years, the internal lubricants necessary for positioning the glass elements (as well as controlling the f-stop) would get stuck in place, so to say.

On the other hand, putting the batteries in for a while, then taking them out again periodically would be a real chore, as we're talking about a dozen calculators, and besides I fear this would result in creating some usage marks on the battery compartment door on the long run, or even damage the pressure pad eventually.

So, I would be very obligued if you could give me some advice on this, and guidelines to keep my Voyagers stored safely for many years to come. Thanks in advance.

Re: Seeking advice from expert HP collectors
Message #2 Posted by Vieira, Luiz C. (Brazil) on 22 May 2002, 2:36 p.m.,
in response to message #1 by John Smith


just a short story of mine.

I kept an HP41CV disassembled in a shoe box for about 9 years. It was spread around the box with some other components. After taking contact with this forum, I decided to build it again and, after some unfortunate attempts, it got back to life (my personal Phoenix 41).

Many things have been told about dried capacitors in here. Everything referred to electrolytic capacitors, standard type, found in some earlier calculators. The HP41 fullnuts being one of them.

I am not completely sure about it, but I believe the Surface-Mount Device (SMD) capacitors used in the Voyagers are tantalum type, not electrolytic type (they look too small). In this case, their 'juice' (electrolytic solution) is absent, say, they don't have it.

I have also an HP15C and an HP16C; their batteries are in their compartments for more than 6 years, and I sometimes trade their places both for checking purposes AND cleaning. Their compartment door seems steady and resistant. It's a pity the HP12C is different now, because its previous batteries' door was the same as the earlier voyagers, so buying a new one would not be hard, if needed.

I'd guess it's up to you. I can't think of an actual reason you should maintain OR not the batteries in place that's not for your own decision. Internal components (semiconductors) will degrade if they are connected to the power supply or not. A small current flow will maintain operating condition as well, and if we think removing the batteries will cause the discharge of each inner capacitor AND replacing them will also cause a small, not regular current surge, then keeping the batteries in place is harmless. Unless you want to keep your voyagers for the generations to come... Who knows how much will they value in 50? 80? 100 years?

Live long and prosper! (and best regards)

Re: Seeking advice from expert HP collectors
Message #3 Posted by Spice_Man on 22 May 2002, 3:59 p.m.,
in response to message #1 by John Smith

I've never heard of capacitors degrading from lack of useage... and I'm not aware of electronics aging faster because it isn't being used... these things usually go bad because of environmental conditions (heat, humidity, static electricity, etc.)

So in my opinion, its safest to keep the batteries removed.

Re: Seeking advice from expert HP collectors
Message #4 Posted by Ren on 23 May 2002, 9:32 a.m.,
in response to message #3 by Spice_Man

Spice_Man wrote: I've never heard of capacitors degrading from lack of useage...

As an electronics technician, let me assure you, there are thousands of 10+ year old Sony built 8mm camcorders that are no longer working because several dozen surface mount electrolytic capacitors in each are failing from lack of use! The particular brand of capacitors they used from about 1988-1992 will start leaking and corrode the surrounding printed circuit board if they are not replaced. If the camcorder is used on a weekly basis they'll keep working. But if you leave it unused for a period of time (4 months in my case) the capacitors are not getting the charge they need to maintain molecular stability. Most electrolytic capacitors will degrade without use due to the electrolyte "drying out".

Now if this has anything to do with the caps in an HP calculator, I don't know...

Re: Seeking advice from expert HP collectors
Message #5 Posted by Vieira, Luiz C. (Brazil) on 23 May 2002, 2:58 p.m.,
in response to message #4 by Ren

Hello, Ren;

May I?

As a technician, and dealing with SMT, is there an easy way to identify electrolytic SMD capacitors? Do they have any particular sign or mark? I'd like to know.

Maybe you know some sort of links to sites where I (we) can find info about them (SMD).

One point: my HP41CV (earlier fullnut) still has all original SPRAGE electrolytic capacitors. They seem to be fine, no visible leakage. Good stuff!

Best regards and thanks for the valuable info.

Re: Seeking advice from expert HP collectors
Message #6 Posted by Ellis Easley on 23 May 2002, 5:55 p.m.,
in response to message #5 by Vieira, Luiz C. (Brazil)

I'm not speaking for Ren, but I think tantalum capacitors are electrolytic. I know tantalum electrolytic capacitors are made two ways: foil and "slug". The foil type is similar to aluminum electrolytics where one side of the capacitor is a strip of foil rolled up and the dielectric is a layer of oxide "formed" on the foil by electrolysis during manufacturing, the other side of the capacitor being the conductive electrolyte which fills, and is connected to the outside through, the can that contains everything. Because the dielectric is quite leaky electrically and is easily breached by excess voltage, the electrolyte allows the capacitor to "heal" after a non-destructive breach by forming new oxide by electrolysis through the application of the "correct" voltage. I understand if you carefully (with very low current limiting) apply an increasing voltage to an electrolytic capacitor over a period of time, the dielectric will build up to tolerate the higher voltage and produce a lower capacitance. The "slug" (or is it "wet slug"?) type uses a solid formed from tantalum powder with pressure and heat (I think the word for this is "sintered") so while it is solid, it is also porous and the particles of tantalum metal have a large total surface area. Sleeve bearings are also made this way from powdered metal so they can be saturated with oil. The capacitor slug is saturated with electrolyte and the dielectric is formed in a similar manner to the foil type.

Tantalum electrolytics usually have less leakage than aluminum ones and the slug type have a very low ESR (equivalent series resistance) and a high capacitance per physical volume, which is the main reason they are so popular in the age of miniaturization. I recently got an HP465A general purpose amplifier (I thought I was getting an oscilloscope for $20! -just kidding) which has several components damaged, apparently because the output was connected to a high voltage for some time. One bad component is the output capacitor which is an axial can, mounted to the chassis with a steel clip, about an inch in diameter and about 3 inches long - 1000 mF, 30V! A quick look in a DigiKey catalog found a 1000 mF 40V axial which is 12.5 mm diameter and 30 mm long. Also a 15000 mF 35V upright at 30 mm diameter and 50 mm long. That illustrates the improvement in aluminum electrolytics since the 1960's. My catalog doesn't have any similar value tantalum capacitors for comparison. I've seen some surface mount aluminum electrolytics that are the can-type attached to an SMD base. I think that because of the higher leakage current, aluminum types need to have some kind of pressure relief seal to allow them to vent, rather than explode, if exessive voltage is applied. Once, in high school, I saw a tantalum foil capacitor blow up in a very interesting display. I've never tried it again because I'm too cheap. Tantalum capacitors are always more expensive than aluminum ones. My catalog has a lot of the can-type aluminum SMD, one advantage of that package is that it can be quite tall for a small footprint for more mF per sq. in. The catalog also shows one type molded aluminum SMD but just a few low values and expensive - $2 to $3 each. It says they have "Excellent endurance characteristics due to adoption of solid electrolyte" - I wonder if that eliminates the need for a safety pressure relief seal? Then it has a number of molded tantalum SMD types.

I watched a news report because it stated at the beginning that there was a connection between high performance video games and a civil war in Africa. I couldn't think of any special components that might be in an X-box that weren't in other kinds of electronic devices. It turned out to be about tantalum. Somewhere in Africa, it is being mined with manual labor in open pits similar to the gold mines in South America, and the proceeds from the mining are figuring into a civil war. I'm afraid I don't remember whether the rebels are buying arms with the takings, or if they are fighting for their share.

Good info (as always in here)
Message #7 Posted by Vieira, Luiz C. (Brazil) on 24 May 2002, 7:58 a.m.,
in response to message #6 by Ellis Easley

Wow! Thanks, Easley. I believe I speak for others, too.

Mam, that's the kind of info we cannot find easily. At least together, in one piece, like this.

One (more) request: do you know some (any) e-address where we can find specs for electrolitics? Mostly manufacturers. I know Philips, Siemens and Sprage (Sprague?). Are there others (and their sites) you know?

Thanks again.

Re: Good info (as always in here)
Message #8 Posted by Ellis Easley on 24 May 2002, 10:52 p.m.,
in response to message #7 by Vieira, Luiz C. (Brazil)

I don't have any particular websites that I use, when I need something specific I usually just take "a shot in the dark" and type in the the company name + ".com". My previous post was just drawn from my experience and a DigiKey catalog! (DigiKey is a mail order electronics supplier in Minnesota. I've never used their website, but it is Also I have a lot of databooks for different kinds of parts, but nothing newer than around 1995.

There is a website called which I found out about a couple of years ago which had made available, for free, an online database, called "PartMiner", of semiconductor sources and specifications that had previously been available only by paid subscription. I used it to find spec sheets for a lot of obsolete parts I had in my collection. They had a lot of data sheets that manufacturers didn't have on their websites - pre-Web content that was scanned from paper databooks. Then, a while back, they changed their policy and started charging for it. I just went there to check the URL, and looked at some email they had sent me. Apparently, the database of current parts is still free but the obsolete parts data costs $300/month or $3000/year! I'm glad I used it while it was free!

Also, the emails indicate that the website has resources for all kinds of parts - they mention "semiconductors, passives, connectors, electromechanicals and more". Other than the special database of obsolete datasheets, the main thing this website did was provide links to manufacturer's websites along with selection help across manufacturers, like, provide a list of all manufacturers that make a certain size memory chip, then provide links to the manufacturers' websites. I've just gone through the registration process again, the system remembered my "organization" (a company name I use when I need one) and allowed me to register. I'm waiting for a confirmation email which will give me a temporary password. I had to provide my phone number - it was the same last time, and within a few weeks, a representative called to find out how they could help me. I guess I can muddle through it again! If you have a reasonable organization to register under (any group pursuing electronics, that might conceivably buy any parts sometime!), you could probably register!

I got my password, but now "the system is not available" - maybe they remember me - I never bought any parts!

Re: Seeking advice from expert HP collectors
Message #9 Posted by Wayne Brown on 24 May 2002, 8:44 a.m.,
in response to message #6 by Ellis Easley

I saw a capacitor blow up in high school, too (in about 1970). It wasn't an electrolytic, though. It was one of those old paper capacitors made with a layer of foil and a layer of paper that were rolled up together and then sealed with wax. In electronics shop we were working on an old TV set that was full of them, and one of my fellow students applied too much voltage to part of the circuit. One of those paper capacitors went off with a loud BANG and a moment later, there were little bits of paper falling like confetti all over the workbench.

The student who blew it up was named Al Hacker. I've always thought he had a great name for an electronics guy!

Re: Seeking advice from expert HP collectors
Message #10 Posted by Ellis Easley on 23 May 2002, 7:16 p.m.,
in response to message #5 by Vieira, Luiz C. (Brazil)

One thing I forgot to mention - the seal on aluminum electrolytic capacitors is very sensitive to chlorine compounds, or used to be. They attack the rubber and cause the capacitors to leak. This limited what kinds of solvents could be used to clean the boards. I notice some of the capacitors in my catalog list the feature "anti-solvent" with a list of types of Freon they can tolerate, I don't know which are chlorinated. Also there are some Philips solid electrolyte aluminum electrolytics, electrolyte is manganese dioxide and they have a ceramic seal.

Re: Seeking advice from expert HP collectors
Message #11 Posted by Ren on 24 May 2002, 9:42 a.m.,
in response to message #5 by Vieira, Luiz C. (Brazil)

Luiz, SMD means Surface Mount Device. That includes, fuses, diodes, transistors, resistors, inductors, Integrated Circuits (ICs), et al. So, to answer your first question, yes, an SMD capacitor is visibly different from a regular capacitor. A regular capacitor has leads(wires) coming out of it, either axially or radially. SMD capacitors have a couple of metallic pads that solder directly to matching pads on the Printed Circuit Board (PCB). The SMD electrolytic caps that have been failing in Sony built 8mm camcorders are small alumini(u)m 'cans' about 3mm in diameter and about 4mm tall. They also have a small black plastic square base. They are silver in appearance and the negative(-) connection on the bottom is designated on the opposite end (top) with by black crescent shaped mark. Again, I don't believe HP used any of the faulty SMDs.

To distinguish a non-electrolytic SMD capacitor from another two terminal SMD device such as a fuse, resistor, or inductor, is more difficult. I'm not sure I know how to tell them always apart, much less describe the differences. But, a silk screened marking on the PCB may give a clue.

I think Ellis did a good job describing capacitors, though I'm not sure I've seen a foil tantalum, I thought all tantalums were sintered.

To find out more about the Sony 8mm camcorder leaky capacitors, do a Google search on the newsgroup using "camcorder" +"leaky capacitors". or Sony camcorder.

Re: Seeking advice from expert HP collectors
Message #12 Posted by Frank Glitz on 22 May 2002, 4:07 p.m.,
in response to message #1 by John Smith

My policy for Voyager batteries: keep in the machine and change every five years. Or when empty, of course (I use the 16C _very_ often as I'm a "near-hardware-programmer", assembler, C and that sort of stuff).

These batteries can be obtained quite cheap (well, unless you let a watchmaker do the change ;-). And you always have every Voyager "ready for use". The five year interval means only 10 changes in 50 years. This should keep the battery compartment doors as well as the contacts "in good shape". And I've never seen such a battery leaking, even over 10 or more years. You should use batteries of high quality though, not the very cheap ones from Asia.

I also never had that "corrosion" effect - well known on HP 41s stored with battery in - with a Voyager.

My first 10C is about 20 years old now. It hasn't been without its batteries for more than a minute and the battery compartment looks like new. It works fine of course.

Hope that helps, Frank

Re: Seeking advice from expert HP collectors
Message #13 Posted by Andrés C. Rodríguez (Argentina) on 22 May 2002, 5:28 p.m.,
in response to message #1 by John Smith

Eventually, silver-oxide (SR44) may be better than alkalines (LR44). As per myself, I would let the calculators with batteries and check them every three months, but I accept is a matter of personal preference; there are valid arguments for both stances.

Re: Seeking advice from expert HP collectors
Message #14 Posted by David Smith on 22 May 2002, 5:48 p.m.,
in response to message #1 by John Smith

Yes, electrolytic capacitors can and do dry out. Much more so in the larger higher power applications. For the low voltage low power application in calculators their life is pretty much the same, powered or unpowered. Power tends to keep the electrolytic film intact but it also causes it to dry out and degrade over time. These two things tend to balance out in the long run. Batteries can and WILL leak. Keep your batteries out of stored machines. I keep my packs in a double sealed small plastic bags so that when they spew it won't be over something of value.

Re: Seeking advice from expert HP collectors
Message #15 Posted by The Expert HP Collector on 22 May 2002, 6:44 p.m.,
in response to message #1 by John Smith

I am an expert collector of HP calculators and what I (and other expert collectors) recommend is that you let _me_ store your collection for you. I know all the advanced techniques for HP Voyager storage and have the climate-controlled facilities for such long-term storage, and the staff who can keep the machines rotated and properly powered, lubricated, and serviced. Of course you will be able to come view your machines at any time, simply call before coming over to arrange an appointment in advance. I'll be happy to help in any way possible, and my service is free of charge.

Re: Seeking advice from expert HP collectors
Message #16 Posted by Paul Brogger on 22 May 2002, 7:34 p.m.,
in response to message #15 by The Expert HP Collector

Now, see? Isn't this just the most generous, helpful group you're likely to find anywhere?

(And I'll bet there's lots of competition offering similar services -- that should drive the price down, so don't just jump at the first offer you come across . . . )

Thanks ! I accept your offer !!
Message #17 Posted by John Smith on 23 May 2002, 6:30 a.m.,
in response to message #15 by The Expert HP Collector

I accept your generous offer to take care of my many Voyagers for me, it's very kind of you !

Please contact me at my usual e-mail address within 24 hours. Thank you. :-)

What a wonderfull world...
Message #18 Posted by Vieira, Luiz C. (Brazil) on 23 May 2002, 8:03 a.m.,
in response to message #15 by The Expert HP Collector

Have you lost your minds?

I believe some guys in here need to talk to D. Mike Meyers.

Hey, Doc, do you do e-assistance?

Re: What a wonderfull world...
Message #19 Posted by Mike Meyer on 23 May 2002, 10:12 p.m.,
in response to message #18 by Vieira, Luiz C. (Brazil)


I do e-assistance more than I'd like to.... But for you guys (and gal(s) Katie?) it's always a pleasure.

I remember fondly the days that this forum helped me mourn for and then resurrect a failed HP-67. I still use it as my daily calculator.

Dr. Mikey

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