Honeywell KFC-225 autopilot - what could cause this failure?

Hi Peter,

I agree; DC servo brushes do last a very long time; generally years of
continuous operation. There was nothing wrong with the brushes in that
roll servo; it was the power amp which went up in smoke...


Looks like a "suboptimal" power amp design. Electronics should not blow
just because of excessive actuation. I guess with all the regs you
aren't allowed to replace the busted part yourself but have to let the
service folks sell you a refurb or new version plus labor.

BTW, the clamp ferrite cores I mentioned the other day might still be pretty useful to diagnose an EMI problem. You can't leave them in there during flight but they are really handy to try out things on the ground, running the engine, keying the mike and so on.


Regards, Joerg

http://www.analogconsultants.com