Quoted from MikeO:And lastly, if connector J124 is mistakenly plugged into the driver board connector J128 (they are keyed alike!), this can cause capacitor C11 to explode.
I can't remember the connnectors, but I had something like that once on FishTales. And also in this case the room was covered with brownish smoke/oil. Oops....
Since then I always check the connectors with the manual prior to powering it up.