As you may remember a few weeks ago  I reported my IV-P TSIO 550 with a Continental 100 amp alternator  B&C  voltage regulator system was popping the field 5-amp circuit breaker in flight after 15-30 minutes.  Many of you gave me good suggestions as I looked for the solution.  Thanks… The problem was finally found and it was caused by a burr internal to the alternator which rubbed through the wire insulation in the diode pack.  I assume as the engine vibrated, randomly the chaffed wire would arc to the alternator case and create a voltage spike in the system and the B&C crowbar circuit would trip the field circuit breaker.  The alternator was replaced and the problem is gone.

Craig Berland

IV-P  N7VG