Electrical Failure on Take Off

[Mark Hislop]

Larry:

There are two types of diodes on the circuit board, located on the top center of the forward side of the front firewall. There are two large power diodes mounted on heat sinks in the center of the circuit board. There is one for each alternator. They act like check valves, making sure that current only flows out of the alternator. That way, if one alternator fails, the current from the other alternator will not feed back to the failed unit. There are also some small signal diodes on the circuit board. They act in such a way so as to determine whether the battery voltage is higher or lower than the voltage put out by the alternators. It is this circuitry which controls the illumination of the alternator discharge and battery discharge lights on the instrument panel. There are also two large capacitors mounted under the circuit board, and they tend to dry out and fail. All of these are components that are easy and cheap to replace.

Mark