funny you mention that, Domain. I had the same thought. I was going to check with the owner, I'll tell her it will cost a little more in labor but we can make sure that is the problem. These people have a ton of money, he's a surgeon, so they just want it fixed. I'll see what she says. If not, we'll just put in that board and if necessary, then change relay board. I agree with old stove, we've both been around too long (lol) but if it was the relay board and the main board was OK, there should have been an error code generated. I'm getting no error code. That usually points to a main board problem.
I work on big commercial washers also, and one of the units I work on in a Dry cleaner friend of mine, has 7 boards in it. Last time there was a problem, I was on phone with factory and it took me and 3 techs on the phone combined 2 hours to determine the problem. And ......... they still were not sure. Aah, I miss those manual oven thermostats of the past. Pop open, pop off leads and check continuity of the oven thermostat. Good or bad. I don't kinow, but give me that and a selector switch anyday.