Unusual HP-21 ?

[PANAMATIK]

(11-11-2017 09:08 PM)jch Wrote:  Did someone already encounter this version?

I have to check if there is some noise on the power supply, and if unsuccessful it will become a host for Panamatik's Woodstock low power module!

Jean-Christophe.

This is exactly the HP-21 board version which I used for one of my low power prototypes. You will need some extra work to install the LP module, because the display driver chip distance is different to normal boards (see LP manual "Replacement").

You can try to apply 6V and -12 V directly from a (ripple free) lab power supply to pin 1 and 2 of the ACT and check if it works. This would proof that the switching power supply is causing the problem.

Bernhard