HP 21 battery charger


Has anyone an idea where I could get a HP 21 battery charger ?


If you can not find an original one, you may use a transformer that delivers 8 volt AC, at open circuit (I mean, with no load), and 200 mA. Polarity is not critical when working with AC. IT IS ABSOLUTELY NECESSARY THET RECHARGEABLE BATTERIES IN GOOD CONDITION ARE CONNECTED IN THE CALCULATOR WHEN USING THE AC ADAPTER. The batteries will filter the half-wave rectified AC and also work as a regulator/voltage limiter. USING THE AC ADAPTER WITHOUT RECHARGEABLE BATTERIES WILL RESULT IN EXCESS AND UNFILTERED VOLTAGE SUPPLY THAT WILL DAMAGE YOUR CALCULATOR. Other option is to substitute the rechargeable batteries with regular alkalines. That will power your calculator OK, but IT IS NOT POSSIBLE TO USE THE AC ADAPTER WITH ALKALINES. And always check proper battery polarity.

Possibly Related Threads...
Thread Author Replies Views Last Post
  HP-67 charger Marcel Samek 3 352 11-22-2013, 10:45 PM
Last Post: Marcel Samek
  HP 21 - How to troubleshoot? Adam Vaughn 13 634 10-02-2013, 09:40 AM
Last Post: Adam Vaughn
  HP charger 82002c for handheld calculators Dave Burson 2 264 05-19-2013, 12:51 PM
Last Post: Dave Burson
  Classic (HP-67) charger issues revisited Matt Agajanian 6 445 05-20-2012, 10:50 PM
Last Post: Matt Agajanian
  HP-35 Charger/Adapter Repair (82002C) LHH 0 173 05-19-2012, 01:21 AM
Last Post: LHH
  aOT--Battery/battery contact care advice needed Matt Agajanian 0 204 04-24-2012, 07:35 PM
Last Post: Matt Agajanian
  HP-67 wall charger Wytnucls 2 250 04-19-2012, 10:13 PM
Last Post: Dan W
  HP 97 charger Harald 2 250 03-30-2012, 02:01 PM
Last Post: Harald
  HP-35A/21 D.MS<-->Decimal degrees routines Matt Agajanian 9 586 03-29-2012, 11:03 AM
Last Post: Matt Agajanian
  21, 45, 32E--which should be next? Matt Agajanian 14 794 03-25-2012, 02:48 AM
Last Post: Thomas Radtke

Forum Jump: