OtisWinslow wrote:
Check that the condenser on the alternator is still grounded.

Why? The capacitor on the alternator is there to suppress brush-noise
Radio Frequency Interference (RFI) at ADF/AM Broadcast/Loran
frequencies (190-1500Khz). It does nothing to suppress Magneto/Spark
noise, which is the original posters problem.

btw-contrary to popular misconception, the alternator capacitor does
nothing to suppress alternator whine heard in the aircraft headphones,
either. That is usually caused by airframe ground loops resulting from
grounding various parts of the audio system (avionics, audio panel,
intercom, mic/headphone jacks, cabin speaker) in multiple, disjoint
places.

MikeM