Andrew H Apple Valley , MN October 21, 2019 Appliance: General Electric Microwave PEB1590DM2BB Ge Microwave Peb1590dm2bb: Microwave runs (heats) with door closed without any heating functions selected. How to replace Smart Board. Replaced the main logic board ("Smart Board"). This board has a relay that energizes the magnetron. This relay failed in the closed position - probably welded itself closed due to high current flow. It is a shame that the board costs $115, while the relay is probably just a $5 item - but you cannot repair the board. Also a little bit of a gamble that a new logic board would fix the problem - but it paid off this time. 4 People found this story helpful Do-It-Yourself Rating: Repair Time Estimate: Less than 15 minutes