Hello Peter,

I've had two of the above fail in under 3 years. They drive the KI229
inverter.



It sometimes surprises me how often equipment fails even though it is
certified. Like vacuum pumps, for example. There has got to be a way to
improve.

Both units developed an intermittent, vibration-related, fault (no
400Hz output) which is curious since they are potted and not a lot can
move about.



The only way to find out is if you can simulate the failure on the
ground, preferably in your workshop, and then immediately probe the
components. In this case most likely the transistors. Toroids can also
fail but that would require a stiff mechanical jolt. I have seen some
that looked ok but upon test showed a reduced AL value. Usually hair
cracks.

Regards, Joerg

http://www.analogconsultants.com