I probed the +12V secondary supply on the control board and saw that it was in a current limit condition, continually trying to restart. I unplugged the connector that distributes +12V to the condenser fan, evaporator fan and LED lighting in the unit, and the +12V supply started and stabilized at the proper voltage. The LED lighting came on as well as the front panel display. Through process of elimination, I narrowed it down to a shorted evaporator fan. Unplugging just that device (with the connector at the control board back in place) everything started to work normally. So, I replaced the evaporator fan assembly and a new blade. All is well and working again.