Recent posts indicate that some have had good luck with Nippon Denso
alternators.  I can only assume that was pure LUCK.  My original alternator
purchased from Lancair was an ND.  It lasted about 2 years.  Upon
disassembly, the problem was evident.  About 160 degrees around the slip
rings was black and corroded.  The rest was shiny.  The brushes were making
contact all the way around.  Obviously, the slip rings were not centered on
the axis of rotation.  I see this as pure shoddy workmanship and absence of
any quality control.

I replaced the ND with a B&C and have been happy ever since.

Remember Pearl Harbor

Bob Jude