I was researching the failure on John Slades EC2 and found some disturbing things. 

 

The input power filter uses a choke which is the only single failure point in the EC2.  The part was originally specified to be so over rated rated such that failure could only be caused by physical damage to the part.  If an overload occurred sufficient to fail this part, the circuit traces on the board would fail long before the part would.  This was the rationale for the basic design approach.  Don't want to get into a discussion of why separate chokes are not used. 

 

At some point the manufacturing facility substituted a different part with same inductance but lower current rating.  It was still over rated and sufficient for any foreseeable situation so it was considered OK.

 

Still later, the board maker substituted an even lower rated part that looks almost identical to the previously substituted part.  I was not informed of this change.   The unit will function normally with this part but it has no extra margin for safety in the event of miswire, shorted output, etc.  I was able to duplicate the failure John Slade had by shorting 1 or more ignition driver outputs to ground or 12V input power.   The original design intent was to allow this condition without failure of the choke.

 

Point of this message is to announce an AD (airworthiness directive) to inspect and verify the type of choke used on your EC2.  Attached to this message is a picture of the three types of chokes used.  The left is the originally specified part.  The center part is an acceptable substitute part.  The right hand part is the unacceptable choke.  If you have this part,  do not fly the aircraft until it has been replaced.  In addition to the visual difference, you can determine which part by measuring the resistance.  The bad part has a resistance over 10 ohms.  The correct parts are much lower in resistance.

 

We will replace the part for you for no charge except shipping cost as specified in the warranty.  This is a simple through-hole soldered part that is relatively easy to replace.  If you are qualified to replace the part yourself, we will send the correct part at no cost.

 

Tracy Crook