Nice range. If you could post a picture of the schematic, that would be helpful. If you don't see the bake element get red hot during preheat, that's the problem. I would suspect the bake relay first, followed by the pushbutton switch and the thermostat. To test relay, turn the oven to bake. Check for voltage to the coil of the relay, probably is 120VAC. If voltage is present at the coil, check for voltage across the contact terminals. 0VAC means the relay is good, 240VAC means it's bad.