HP-65 - 1601A03250 - Compatibility Issues ? - Advice needed

[teenix]

(10-07-2019 09:24 PM)albertofenini Wrote:  ...
We re-assembled the issue with the top row keys was gone.
...
Surprisingly when the unit looks locked in some unknown state, it still can read cards

Possibly a poor connection which was cleared when changing the board around. Pin 18 of the CPU to keyboard connector controls the keyboard row for the A - E keys from the CTC chip in the hybrid circuit (pin 22).

The card control is by hardware in the 65. As long as the CPU board is functional, card access should work even though the microcode is not working as it should. This couldn't happen in the 67 as card access is hardware and software controlled.

This makes the 65 more "finicky" with card access because the card reader motor speed has to be closely matched to the CPU clock rate.

cheers

Tony
cheers

Tony