Things that make you go Hmmmm? Part IV

The case of the blown fuse, or rather the blown up fuse:

Blown 10 amp fuse on Harris SX5 PA board
Blown 10 amp fuse on Harris SX5 PA board

F32 is blown into small bits and had to be vacuumed out of the bottom of the transmitter.  The reason why is the pair of MOSFETs connected to that circuit were shorted.  Of course, the reason for the shorting of MOSFETs needed to be investigated.  What I found was on the underside of the PA board where the brass stand-off attacked the toroid combiner board, the nuts attaching the stand-off to the combiner board were loose and there was a big arc mark.

I tightened everything up and replaced the MOSFETS, marking them with a pen in case they short again, in which case the drive section needs to be closely examined.

Print Friendly, PDF & Email

Leave a Reply

Your email address will not be published. Required fields are marked *