Inexpensive Temperature Feedback Controller for the Varian 63 CRA

Construction details and the performance of a temperature feedback circuit added to the power suppy of a Varian model 63 furnace atomizer are discussed. The circuit incorporates a photo transistor temperature transducer and approximately $25 worth of readily available electronic components to implement both a variable temperature ramp rate and a variable maximum temperature function. The normal mode of operation can be selected if desired.