Produces high voltage according to the potentiometer setting. PWM puls width is contolled through feedback line from the HV output. Work with 1-2 tubes (approx 3-6 mA load) @175V .
You can turn on/off the Nixie tube load with the switch and check as the PWM duty cycle changes according to the new load( current measured on the output of the converter)
300K gives the minimum load.
The error voltage operational amplifier has an output voltage limit betveen 0,5-4,5V, this is compared with the waveform generator (0-5V) signal, which limits the minimum and maximum duty cycle of the PWM.
