HP-65 more on the card reader

[wallyt]

With reference to your waveforms for WB, as you noted there seems to be a lot of noise there. Have you used your scope to look at all of the power supply voltages to verify that they are clean DC? Scope all of the voltages from the power supply on the logic board to make sure they are clean.

Are you powering the calculator from a battery pack or external supply (is it clean)? Did you check or change the capacitor on the motor? Isn't there a filter cap on the keyboard for Vbsw?