"John Clonts" writes:

As for bad diodes; I trust my ears....

What do you mean by this? That you hear something distinctive when a
diode goes out? Do you hear it directly, or is it through your headset
or audio system? What does it sound like?

With all six diodes intact, the rectified DC from the 3-phase AC
waveform is reasonably low-ripple. Lose a diode and that takes a
chunk out. On a car, you can hear the whineeeeeee change pitch in
the radio, esp. AM, as you go through the gears.

See http://www.allaboutcircuits.com/vol_3/chpt_3/4.html and look at
the "3-phase full wave bridge rectifier" and the waveform below. Now,
take away the blue and see what it looks like....

But as a pilot, you are far smarter than Fred Freeway. You can
usually tell a bad diode without listening, just by the ammeter
readings. Not directly, but rather from knowing your aircraft.

Make some tests: run landing lights before approach, and at X rpm,
you see Y amps. Make a note. And so forth...If one day, it makes
about 30% less current than it normally does, in similar circumstances
[i.e. climb-out from your home field, at X rpm, for n minutes..];
be suspicious....

One confort: You'd think that losing one diode would increase the
strain on the other 2 and THEY'd soon fail as well. But I've seen
'whiners' that lasted for months. I guess the diodes are usually
NOT the weakest link; the ones that fail are not from overheating
but other causes [bad bonds, vibration, etc.]




--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433