[Piper J3]

The FlightCom 403 in my RV-12 quit working. I removed the unit from the panel and heard something loose inside. I took off the top cover plate and discovered a nut and insulator bushing the holds a power transistor heatsink vibrated loose and fell on the circuit board. The remaining screw without its insulator allowed the power transistor to short-circuit against the metal case. The real problem is when the 403 quits working it prevents audio from the comm radio to reach the headsets.

A new (used) 403 is now on order and I will remove the top cover plate and put some adhesive on the exposed thread to prevent recurrence.

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[Harvey rv12]

Wow, great diagnosis!, to bad it fried the board.
Where did you find the used one?.

 

[Piper J3]

eBay - $90.00 shipped

 

[RFSchaller]

The only time I ever lost comms was when my alternator and battery went out on my Cherokee. Naturally it was the one time I had left my portable comm at home. I shut off everything but the XPDR and had enough juice to squawk 7600 and fortunately got a steady green from the tower. Fortunate because I pretty much forgot all the other light signals! When selecting 7600 I inadvertently went thru 7500 which woke up the boys in PHX TRACON.