HP-19C/HP-97 printer Message #1 Posted by Tony Thimet on 12 Dec 2003, 9:13 a.m.
Hi all!
As you probably know the HP-97 and HP-19C won't work at all from the external HP power supply if there is no battery pack installed.
To get around this problem I used a regulated DC 7.5V off-the-shelf supply: Now the units work fine - however the printers won't work!
Apparently, the internal circuitry of the calculator does not allow to draw the necessary current from the external power supply but only from the installed battery pack.
Does anyone have more experience with these issues? Is there somwhere a schematic of the calculator's voltage regulation/battery charging circuitry?
Many thanks,
Tony
|