Woodstock collectors: electrical care/prevention tips and practices?


Hey all,

In the process of finding new homes for the HP27 calculators that I propitiously found at a local-ish university surplus sale, I've come to the conclusion that (unless I'm missing something) there isn't any real SOP about how to take care of these calculators, given that they are, shall I say, electrically sensitive.

For those of you who have Woodstocks, what are your thoughts? Particularly about:

-- Plugging the calculator into the wall. (E.g., is there ever a good reason to do this?)

-- What types of battery solutions are available?

-- 1.5V alkalines vs. 1.2V rechargables. (E.g., are 1.5V cells okay for long-term use?)

-- Is there a "best way" to safely charge the batteries and use the calculator to sustain its longevity? What strategy do you use?

I've found a lot of related information on this site, but scattered across different topics. Hence this post, to hopefully consolidate. I'm thinking that if we can get enough authoritative (or authoritative-ish) info for a FAQ or SOP then it can be re-posted as an article.

If you have any thoughts, I'd be curious to hear it.


My failsafe strategy is to NEVER plug the AC adapter into the calculator and wall, regardless of the condition of the batteries or whether or not the calculator is turned on. I use ONLY flat top 1.2v AA NiCads, and only charger them outside the calculator. I recently found a power pack charger so I no longer need to remove the battery cells from the holder in order to charge them.

Whether or not all of these precautions are necessary, I do not know, however, all my Woodstocks have remained functional over the years and I sleep comfortably.

Operating the calculator while the AC adapter is connected is risky, even if good NiCad batteries are installed, because if the electrical connection between the battery and calculator is not perfect, serious damage can occur.



I totally agree with the fact that it is not safe charging the batteries while using Woodstocks, but it is harmless to charge the batteries while the regular Woodstocks (not the Continuous Memory type) are switched to OFF. By analyzing their circuits, the AC adapter is isolated from the calculator circuitry for as long as the ON/OFF switch is turned to OFF.

Anyway, some circumstances must be considered:

IF the batteries' contacts fail and you inadvertently switch it to ON, then you may regret that good time...

In the particular case of the HP27, which uses N-MOS circuits that are not compatible with the circuits from other Woodstocks (cannot donate to nor receive from other Woodstocks than another HP27)

The new batteries are different of the ones used some 30 years ago (ampere capacity, charging time/current, etc.) and these oldtimers would not charge these batteries accordingly.

SOOO... just let the batteries 'eat' energy from an outside source. It´s not worth the risk of burning such fine, rare and expensive HP27´s.


Luiz (Brazil)

P.S. - BTW, if there is any possible, tinny chance of selling one of these, a friend of mine here in Brazil is dying to have an HP27. Not me, a friend, really!

Edited: 28 June 2010, 4:14 p.m.


Hi Luiz,

I think your sentence beginning with "In the particular case of the HP27" was truncated. Or am I just mentally missing something?

Re: HP27 availability. Alas, all five of the ones that I found are now at new homes. That said (and with no regrets), it would have been fun had I heard from you earlier, as the first four ended up on four different continents (without trying). The sale of the fifth to South America would have diversified their distribution even further. Five calculators on five continents: that would have put a smile on my face.

(If you're of the teaching that North and South America are a single continent, ignore me.)

Edited: 28 June 2010, 4:38 p.m.


The sale of the fifth to South America would have diversified their distribution even further.

Even further than we could ever have imagined :-) link


Awesome! We Americans are so worldly.

(Come on, who doesn't know that South Africa is located just south of Mumbambu ?)

Edited: 28 June 2010, 7:10 p.m.


I almost died laughing at this (fortunately (?!) my wife tells me that the Onion News Network is a spoof!). That was great. I am already planning my first trip to Mumbambu!


If you liked that one, I recommend looking at some of their others. They're consistently very funny.

On the topic of technology, I highly recommend this one.


Can we have the HHCC in Mumbambu this year...?

On another note, a friend of mine says he was at a party one day. Someone asked "what is the capitol of Africa?" Without missing a beat he answered "Swahili." We American's can be so stupid sometimes.


In this case, I would go. Go Mumbambu!

Luiz (Brazil - in the south of America!)

Edited: 30 June 2010, 9:48 a.m.


I think your sentence beginning with "In the particular case of the HP27" was truncated.
Yep, you are correct. I thought about writing:

'This is even worse in the particular case...'

Then I worked it out and intended to write:

'In the particular case of the HP27 this is even worse...'

And I ended up missing the 'this is even worse' part of it. I left home right after that and went back right now.

Thanks! (I hope now it is everything in place...)

About the America: geographically I see them all as one America only (hence a single name), but I must consider three of them as for their different people, cultures and history living in three different 'slices'. I cannot only take the fact that the three 'slices' are joined by common land (no ocean between them) because Europe, Asia and Africa also have a lot of joined lines.

Luiz (Brazil)

Edited: 28 June 2010, 9:57 p.m.

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