HP-41CX Halfnut problem cardreader with Nov64d

[Diego Diaz]

Hi Ralf,

This may be related to the differences from Half/Fullnuts power supply. Being the halfnuts a bit weaker than the fullnuts.

The demanding card reader motor can cause a dropout in the power line (V+) affecting the functionality of the NoV-64d and causing noise in the bus, which renders the "CHECKSUM ERR".

Again, I don't have a Card Reader or a Halfnut here, but you can check if the problem persist when configuring your NoV-64d in a Clonix-D fashion; this saves a few mAmps and may help the Card Reader to perform as expected.

Also, trying new fresh batteries or external power will give a glimpse of the power supply behaviour.

Sorry not being of much help on this, I've got very limited resources here. I can offer a much detailed diagnosis once I get back home next month.

Best wishes.

Diego.