The ultimate collectors piece for both LED and vintage calculator lovers - the HP-01 by Hewlett-Packard of USA. Considering the year of introduction (1977) it is a bit surprising that they didn't choose a LCD display but this way or another this wrist calculator was the most advanced piece of personal circuitry that you could buy in those days. Unlike the first 1975 Pulsar or even the earlier 1976 Hughes/CompuChron wristwatch calculators the HP-01 is a genuine computer providing advanced functions and calculations not far from scientific calculators of that period. Except the basic time, date and calculating functions it also has a timer, stopwatch and alarm. The watch case is heavy and extremely large with high quality craftsmanship either Swiss (steel) or US (goldfilled). Enjoy this exposed strip-down review for the first time on the WWW.



The keyboard is robust and has four exposed buttons for Time (T), Date (D), Calculator (M) and Timer (A). The Stopwatch can also be accessed with a fingernail  by pushing a slightly recessed S button and reset with R (both in top row). All of the other recessed buttons require a pen tip or stylus that is smartly supplied in the clasp or in a two-sided pen by Garland (the same that made them for Pulsar). The watch has a convenient quick-release clasp that allows to place the watch flat on a desk for easier use. The watch head consists of two main parts - the bezel with keyboard and case with bracelet which are combined together with a screw-down ring (the larger one) that needs to be turned clockwise to remove the bezel. This construction is slightly over-engineered but is not that complicated as it might seem at first glance.



When removing the bezel you must hold the inner black (battery) plastic carrier so it does not rotate with the ring. This is essential to prevent any damage to the quartz crystal or trimmer. The black battery carrier is held in place with another smaller ring within the larger ring and needs to be turned counter-clockwise. It can be removed at any stage, even when the bezel is still in case, to make access to the quartz crystal. If a quartz replacement is necessary you might be in for a big surprise as the HP-01 uses a special 38.4kHz that is higher than the popular 32.768kHz. Some sources might have these available so check Mouser for instance. When you succeed with removing the battery carrier you will need to "unscrew" the larger ring  from the bezel. It is cut on purpose to allow removal (check left picture).



Once the ring is gone withdraw the module which will either fall out or might require a small hook to pull it out from the bottom side. The substrate is made of ceramic so DO NOT try to pry it upwards intensively. If the module sits firmly you can also try to push the keyboard slightly! The module consists of a display substrate and keyboard panel with conductive tape mounted on top of the circuitry. Sticky or unresponsive button contacts might be cleaned with alcohol or a fibrebrush. The keyboard buttons are secured in the bezel with a rubber layer that provides some flexibility at every push. There is not much to repair in a HP-01 but  the most frequent issues would be caused by a broken quartz, dirty/broken trimmer or a resistor above the display. Missing display segments might be caused by bad solder joints on the display substrate or... to much pressure from either of the two rings mentioned above.



This HP-01 is a dream come true and has been acquired from the original owner Timothy O'Hara from  California, USA. He bought it new in 1977 and swapped it in 1984 for a Rolex from his brother. From that time until 2010 it had been stored except for special occasions when Tim fired it up to amaze and entertain himself and others. "There was nothing like it back then, and it's still way ahead of it's time".  I'm not surprised as I'm amazed with it just like Tim was in 1977. He almost wrecked his car getting it home by messing with it and looking at it while driving :) Tim has provided me with lots of history and all the extras shown below including the original opener/battery container that cost 3$ (HP#82080A) and pen refill (HP#82065A) for a buck :) Btw. the manual is a must as the average owner is not as clever as the brains at HP!


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HP Internal Corporate Bulletin June 1977 is here

HP Internal Corporate Journal December 1977 is here

Keywords: hewlett-packard calculator watch, hp01, hp-01, hp wrist calculator

Market value: 500-2500$ (goldfill or stainless, condition, box, papers, extras)

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