I have an older Blue M oven that I am having trouble regulating the temperature. The style of controller is called Power-O-Matic 60. It looks like a split transformer with a pivot on the bottom that closes the top of the transformer end when the temp dial is closed. The weird thing is that the thermocouple Blue M does not even connect directly to the transformer unless it is thru the housing. The 240 single phase powers the heating elements diretly and then thru a large transformer that has several 77V and 100V center taps. These center taps connect to another transformer connected to this variable dial for the temp control. When the controller dial is in the lowest position I get no volts and when it is wide open I get the 100V from the center taps. However there is not much precise control. The voltage tops out at too low of a temperature.
What can I do to repair this without buying a new controller? Can I get some variable AC voltage source and test it? No Actually I would need some type of resistor decade box to control the feedback voltage since the dial control is only generating resistance I assume. The oven is rated at 19 amps 240V. Any Ideas on how to further bench test it? Some of the symptoms are not enough heat - I need 105*C and sometime have to set it for +200*. Any help would be appreciated.