HP-35 Power Supply Waveforms

[teenix]

(04-07-2019 08:33 PM)cruff Wrote:  If I remember correctly Vcc is the LED drive voltage and Vss is the voltage for the remainder of the calculator. Has anyone taken measurements? Perhaps several hundred mA for Vcc and 50 mA for Vss (which might represent idle and no card reading)?

The LEDs and card reader motor circuitry is controlled by the CPU but powered directly from the battery. it is a complicated setup but works well and keeps the power supply design simpler.

cheers

Tony