Was doing my IMC renewal and suddenly horrendous crackling on the radio. So bad we went 7600. Tried turning off things but no help, eventually found we could stop it completely by reducing power under 2050 rpm. Traded speed for silence and completed flight. On subsequent return flight every time we crept past 2050 if started again. Any ideas what's causing it? Haven't flown her since we got back - but expect same problem if not fixed!
Notes: Couldn't isolate alternator as no split master, and circuit breaker not the type you can pop. A/c is old Cessna but with newish O-360. Noise was staccato crackling, not a whine. Earlier when starting, had had occasional flashes from low volt indicator - had thought caused by old and lazy beacon - when off, no flashes. There are no strobes on a/c. Suggestions include alternator suppressor failing - but I thought that was anti-whine rather than crackling. Regulator?
Anyone had similar experiences and/or is clever enough to know what I need to fix?
