Michael wrote:

In case you ca

Of course I care. Hence the secretly placed bait, which you
thankfully took!

Most mag installations in modern (read - designed for electrical
systems and radios) aircraft have a capacitor between P-lead and
ground. This absorbs some of the electrical noise, and generally
reduces static on the radios.

Very interesting. Over the last three months I have been having mag
noise problems (pop-pop-pop on frequency) whenever I used the Garmin
G430 com radio and full power, almost exclusively when tuned to a higher
frequency (130.00 or above). This interference did not occur with the
older B/K comm radio I use as my second radio, so I would end up using
the B/K radio during cruise.

When I asked a trusted avionics shop about this, they explained that the
mag itself was causing the interference and that the Garmin circuitry
was more sensitive to the interference than the older B/K radio. Based
on your explanation, I wonder now if it was really this capacitor
showing signs of imminent failure?

These capacitors fail with depressing regularity, but they usually
fail 'open' - that is, they stop doing their job and radio noise
increases, but the mag keeps working.

Good to know.

This is the first time I've
heard of one failing 'shorted' - but if one does fail shorted, you
ground the P-lead and it's as if you turned the mag off.

That is almost word-for-word how my mechanic explained the mag failure.

Thank you for your explanation.

--
Peter