Reinstalled the MGL iEFIS panel, connected LAN and power cables. The setup had been used for several hours earlier in the week to update firmware on iEFIS and iBox. A thick brown, acrid smoke came from the iBox, with the iEFIS showing sensor alarms. Shut the system down immediately, but too late to prevent damage.
On inspection, one of the large diodes on the iBox board was damaged, which in term damaged the circuit board traces and nearby IC. Although I was unclear as to what and why the failure occurred, the iBox was returned to MGL for examination. MGL was unable to repair the unit. The failure mode suggested was that the DB-9 carrying the power was improperly attached to the DB-9 CAN bus port.