HP97 charger


I was looking at the service manual of the HP97 from the DVD set

By looking at different schematics, I have the strange feeling
that the HP 82031A charger (see page 5-1) is only a 220V to 12.8V AC transformer.

See also the figure 5-10 for HP 82037A schematic diagram page 5-3/5-4

Can someone confirm this or I completly mis-read this doc ?

Thanks in advance


Yes the charger is just a transformer see schematic figure 4-10 on page 4-15 you will see the charger input goes directly to a bridge rectifier. I use the North American 110V charger 82059 the output of it is rated for 8VAC 3VA.


In page 2-5, and figure 2-10 it is said that

"the ac adapter/recharger is a transformer that drops the line voltage to 12.8 Vac at the input terminals of the calculator"

So is it 8 Vac or 12.8 Vac ?

Elsewhere we can find other reference for topcat adapter such as
82066B 8 Vac for 7 Watt

A 220 V to 12 Vac rated 1A is easy to get, a 8 Vac isn't ...


Near as I can tell the chargers all have a rated output of 8VAC 3VA. The unloaded output is about 12.8VAC but drops to about 9.7 VAC when connected to a 97 with a good battery pack and drops to about 8.7VAC when the 97 is turned on.


Thanks for the info,

I will try with a linear 9 V ac 3,5 VA adapter. The drop from the transformer at 8,7 V under load should be ok ?

It's a mascot 8310 (see http://www.mascot.no/?CatID=1179)


I would suspect that will be ok, it is a little lower than what I observed with the HP charger. A lower input voltage would be better than higher at worst it would not be able to maintain the battery voltage and charge the batteries, but with 8.7Vac input that should not be a problem. A fully charged battery pack with good cells should be about 5.5 to 6 VDC.

Possibly Related Threads…
Thread Author Replies Views Last Post
  HP-67 charger Marcel Samek 3 1,771 11-22-2013, 10:45 PM
Last Post: Marcel Samek
  Disaster: help for a couple of HP97 needed! Jose Gonzalez Divasson 10 3,030 01-21-2013, 04:45 PM
Last Post: aurelio
  Charging Current in HP97, 82143A, 82162A Les Wright 5 2,079 06-17-2012, 02:11 PM
Last Post: Les Wright
  can you identify this HP97-67 book? Ignacio S├ínchez 4 1,937 06-13-2012, 01:02 PM
Last Post: db (martinez, ca.)
  HP-67 wall charger Wytnucls 2 1,351 04-19-2012, 10:13 PM
Last Post: Dan W
  HP 97 charger Harald 2 1,280 03-30-2012, 02:01 PM
Last Post: Harald
  Which charger for a35 Matt Agajanian 3 1,526 03-23-2012, 02:58 AM
Last Post: Marcus von Cube, Germany
  more HP97 card reader followup. Dave F 4 1,583 12-02-2011, 10:06 PM
Last Post: Dave F
  HP97 card reader followup Davd F 14 4,206 11-25-2011, 02:06 PM
Last Post: Dave F
  Aristo M85 -- What charger? Gene Wright 9 2,891 11-03-2011, 04:56 PM
Last Post: Mike (Austria)

Forum Jump: