HP Forum Archive 12

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HP-21 Circuit Diagram Schematic Message #1 Posted by Gordon Dyer on 12 May 2003, 6:50 p.m. I have found a circuit diagram for the HP-21. I don't know if it is accurate but it is worth a look if you are interested. http://www.cs.ubc.ca/~hilpert/eec/ Click on the calculators link at the top of the page, then click the HP21 link and then click TD23 Data: view That should get you to hp21.gif

Re: Any Intewrest? HP-21 Circuit Diagram Schematic Message #2 Posted by Gordon Dyer on 13 May 2003, 2:11 p.m., in response to message #1 by Gordon Dyer Was anyone interested? I would like to know if it is accurate.

I downloaded it... Message #3 Posted by Vieira, Luiz C. (Brazil) on 13 May 2003, 3:53 p.m., in response to message #2 by Gordon Dyer ... but missed the "Thank you" share. It's been quite noisy, busy morning here... Thank you, Gordon; there are other good sources there. Best regards. Luiz C. Vieira - Brazil

Re: I downloaded it... Message #4 Posted by Ellis Easley on 13 May 2003, 11:13 p.m., in response to message #3 by Vieira, Luiz C. (Brazil) Yes, thanks Gordon! I'm going to ohm out the common portions of my HP25 and then maybe I'll figure out a way to add the additional chips to the schematic.

It's the same one I was sent from another contributor Message #5 Posted by Vieira, Luiz C. (Brazil) on 14 May 2003, 12:22 a.m., in response to message #4 by Ellis Easley Hi, Gordon; I opened the file and I saw the additional circuit to suppress batteries when using external AC Adapter. It's the same one I was sent form another contributor. I know who is he, of course (thank you, R.) but I keep my policy of never mentioning a name associated to particular gestures before asking for permission. I know you all understand that. But I was not aware about where did it come from, and now you, Gordon, have opened the box. Thank you very much. Best regards. Luiz C. Vieira - Brazil

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