Schematic and Woodstock Data


Hi Gordon,

Yes, it's very interesting. I just got back into collecting by getting a 21 last week. This is a very timely contribution.

The schematic does contain one error. On the ACT (big chip), pins 13 and 14 are shown connected to two capacitors in parallel. That should be a capacitor and inductor in parallel. According to a message in the Archives, the values are 330 pF and 150 uH, giving a resonant frequency of 715 kHz.

I've been going through the Forum Archives looking for Woodstock-related material. I'm thinking of summarizing it all as an Article. Two questions: is there any interest in such a summary? And, would it be necessary to cite each individual message for each item I report? It could be done but would add substantially to the effort. I could cite contributions by name instead, to give proper credit. How about that?

Thanks again for the schematic.

- Michael


Luiz and Dave Hicks and I have talked about finding a way to group info from the Archives into FAQs or something like that. It's a daunting task in general! My interest originally arose because I was searching the Archives to look up specific subjects and thought I would just keep an index of the useful messages I found categorized by the subject. I'm afraid I haven't made any progress on the big project. However, I have a system I use to save interesting threads: rather than just save an HTML file for each message, I copy the text from the subject line to the end of the body of the message and paste it into a Word document (to preserve fonts, etc.). I type two newlines between messages and put a complete thread in one document. By copying as much as I do, there is enough information to see the order of the messages in the thread. I want to experiment with automating this process, then grouping threads on the same topic with a keyword search. The problem I always come up against when I ponder this idea is that to summarize to any degree, I would need to apply some editorial judgement. But Dave pointed out that he won't be able to keep the complete set of Archives online forever, so some kind of summarization will have to take place in order to keep the most useful information available online. The Articles Forum is the logical place to put such summaries. I wonder if there is some way to make this interactive or a group activity - so anybody who uncovers a useful thread or message in the Archives can add it to the relevant FAQ, for instance.


Hi, Ellis;

some months ago, last year, I sent an e-mail to David telling him I was p... off because I lost a large text file, about 8MB large (text only) with colllection of calculators usage posts. I simply overwrote it for a new 100K without seeing. Waste of about three months of work and I decided to give a break for a while. It's indeed a daunting task...

My primary interest was collecting realted data in a "big file" allowing subjects being read separately.

Ellis wrote:

I wonder if there is some way to make this interactive or a group activity - so anybody who uncovers a useful thread or message in the Archives can add it to the relevant FAQ, for instance.

At the moment format is stablished and contributors can do it in a regular basis, it is actualy great idea! Fun and obscure, unrelated comments are inportant at the moment the subject is rising, but when other subjects come to the arena, it's good idea to "filter" existing texts, allowing a faster read.

I'm getting back to business soon...

Luiz C. Vieira - Brazil


At least some of the more useful threads end up as articles in the "articles" area here. There's quite a bit of useful information already there, so why not simply add to it by condensing other useful threads into articles. Editorial oversight would be provided by whomever is condensing that set of articles, hopefully someone on this forum who has expertise in that area.


Thanks all, for your comments so far.

You're right -- indexing the entire Archives is a daunting task. That's why I'm not doing it. By concentrating on just one topic, I think I can reduce the task to something reasonable.

Katie, with all due respect, I don't think the contents of the Articles really reflects the knowledge base out there. In the time I've spent here (about three months active participation preceded by perhaps six months of lurking), I have seen many people write stuff of lasting value. Others chime in and suggest that the material be reposted as an Article. This is almost never done. The material is not exactly lost, but it's not really accessible unless someone spends the considerable effort to wade through the Archives. (You are the exception, someone willing to take the time to make your information readily available as an Article. I've found them very helpful. Thanks!)

I've only looked through the last two archives so far, yet I've found lots of interesting material. Much of it consists of little tidbits; not enough to justify an Article. Yet the sum total of all the tidbits is not inconsiderable. And who knows -- some little fact sitting around in Archive 4 might hold the key to someone trying to bring, say, an HP-25 back to life. If only they could find it.

I don't want to solve the problems of the whole world, or even of this Web site. But since I've always had a thing for Woodstocks, gathering all the existing material on them would be useful. It would also allow me to give something back to this community and make it better. And, yes, it would also serve my sefish desire to learn as much as possible about these wonderful machines. Which around here, I suspect, needs no explanation nor apology.

- Michael


I too would like to see more postings show up in the articles forum in some fashion. Luiz and Ellis are struggling with doing something in the broader sense but I'm sure they'd be happy to have someone take on the Woodstock part. (And they probably wouldn't mind a few more volunteers...)

Authors should be cited if you quote anything directly (unless you talk to them and they tell you they don't care). If instead of quoting, you learn from posts and then rephrase it in a cohesive article of your own words, then a detailed list of citations is not strictly necessary but I would really like to see people who contributed major ideas getting credit.

As Ellis mentioned, it's best to suck everything into an article rather than pointing into the archives. The archives are still a manageable size but I can't guarantee they'll stay that way "forever".


I would paraphrase the stuff I use. Original authors would be credited. I may include my own comments where appropriate.

I don't think I'll end up with a "cohesive article," to use Dave's phrase. It will probably end up as a collection of small items, similar to MIT's old HAKMEM. (Recommended reading if you're really into math and computers.)

Here's a possible sample; found near the end of Archive 9, 29 Aug 2002.

Covering Charger Port

(Dave Smith) To keep from accidentally plugging the battery charger into a calculator, cover the charger port with Kapton tape. (Used when flow soldering printed circuits; leaves no residue.) Especially useful if lithium batteries are being used. [If I want to add my own comment, it would be in this format - mfc]

I'm trying to keep it simple. Anyway, I'm going to start collecting material now. Maybe in the future, when the Archives are indexed my compilation will still be useful.

I do have a couple of questions about the Articles Forum. When something is posted there, is it possible to revise the article later? Or are we stuck with it forever? And is there any way to include drawings, diagrams, or photographs in Articles?

- Michael


Hi, Michael;

as mentioned, I and Ellis offered ourselves to build "something" related to ease the job of finding literature based on existing contributions. I wrote build "something" because part of our discussion was exactly the way subjects would be found and shown.

I think final documents in plain text with related graphical support (as you wrote) is the best when memory use is also an issue. As an example, if we have specific articles about usage and programming techniques in FAQ format (as Katie mentioned in this thread) mainly based on facts found in posts, these articles should complement already existing Dave's database for each calculator series. You see, how many times I wrote posts (I already have the basic text saved, for instance) when newcomers or even regular contributors ask about how to change comma for period in some models, or how to perform sef-tests, or how to change number format, or... If we have these subjects already condensed in one or more articles (calculator basic operation), it would be easier to add the link. Also, at the Forum's Welcome header, Dave could add a fourth line to the three existing ones ("Classified Adds", Advanced Format Techniques" and "e-mail me") inviting people to [italic]"check for existing FAQ-like articles at the MoHPC site"[/itlaic] for main subjects because maybe the answer for their question is already there, among other important facts. I believe this would be complementary data, and the name of those who contributed would be relevant only when actual addition (something not found in manuals) is made; something like: [itlaic]"According to Peter's researches..."[/itlaic] and the text describing Peter's founds. This would lead to further corrections, changes for additional credits and new material whenever needed.

I think final read-me text with existing MoHPC format is fine, but a more elaborated PDF to be downloaded, with specific TTF and additional text format, would also be desirable. This sort of document could be generated after we have a concise, refined, error-free (or almost) document. And this is what I think that should be a goal, because existing HP related material is available at the MoHPC CD's/DVD's, but MoHPC own PDF's or part of them might be available to be downloaded directly from the site and also available at the CD's/DVD's. And this would lead us to complete documents, with authors and contributors. Something to be thought about.

Well, I had a large plain text with many basic posts (main text) already "set-up" and ready to be refined when I inadvertently overwrote it! I wish I could kick my own a.. for that, but thanks God I have no such ability. More than a month of spare time on reading, collecting, comparing, cutting-and-pasting... thrown away. Tha heck! I'll do it again. I was a lot p... off at the time it happened, now I just need to synchronize watches and start again.

At the time, a brief discussion about finding themes was the starting fire, as we have in this thread. I thought I could show a first concluded task and ask for comments, suggestions, etc., so we could focus on each and every additional suggestion over an existing start point. Sometimes it's easier having a reference so we can build our own concept. In this case, there are already many good suggestions and no place to make them happen; if at least an actual text is ready as a target, shooting would be easier, don't you think?

I'll soon find a way to get something ready.

Thank you all and best regards. I'm willing to read more and more suggestions.

Luiz C. Vieira - Brazil


I don't know if 715KHZ is the right freq unless the ACT then divides it by 4 to get the 180 KHz PHASE1 and PHASE2 clocks.


Hi David,

My 21 is in pieces so I measured it. The oscillator frequency (ACT pins 13 and 14) is 695 kHz and is divided by 4 to get 174 kHz on the phases (ACT pins 16 and 17). (I don't know which pin is which phase though.)

The Classics work in exactly the same way.

- Michael

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