Power Designs 2005A Heater Circuit

[BarryBreaux]

Hello,

I have made a lot of progress on my PD2005A. I have replaced all the burnt components in the oven and I am getting good results on the output. I have designed a new circuit to do PID control on the heater. I am currently looking closely at the PD heater circuit to see if I want to interface with it or roll my own. So now you know where I am going...

I can't get my head around the PD heater circuit which consist of a few resistors, a SCR, and an NPN resistor. I put it in a simulator and can't get it to function properly simulating the thermostat. I don't know if my 2005A is functioning correctly. If you understand how this circuit works I would appreciate enlightment.

Thanks

Barry