I have Jenn-Air down-draft model SVE47600W bought in 2000. I recently started having problems first with the display which went completely out. The oven seemed to work ok as well as the stove. I turned the power off, removed the EOC to look at it and then replaced it but now not only does the display board not work but the membrane switch does nothing either. No beep, no anything. The membrane tail does not appeared damaged and I was careful to remove it from the display. The 12Vdc supply voltage from J1 is 15.0Vdc and the manual says it should be 12Vdc. Several of the other J2 voltages (ac and dc) differ from the published values. Could this be a bad relay board or display board causing these problems? I don’t want to get stuck with parts and the expense of parts I don’t need. 
Any advice? Thank you. Mike