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Date: Wed, 23 May 2012 11:17:45 -0400
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Subject: Re: [LML] B&C sd-20 backup alternator
From: Colyn Case <colyncase@earthlink.net>
In-Reply-To: <list-5555223@logan.com>
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References: <list-5555223@logan.com>

Paul,

My understanding: Bill sources the parts in China or Japan, balances =
everything and maybe tweaks a couple other things, and then puts his =
name on it.    Given the stator doesn't need to be balanced, could you =
find the overseas source and solve your problem that way?

Colyn

On May 23, 2012, at 8:17 AM, Paul Miller wrote:

First, I'm happy with the unit, 582 hours and 8 years before failure.   =
Second, if anyone has a core unit they want to trash, please write me =
offline.  I need a stator.

In the Legacy, I normally get low voltage on this unit until 1800 rpm or =
so.   There have been some symptoms but nothing pointing to the =
alternator.   This past weekend, the light stayed on with zero amps.  =
Long story compressed, the wiring in the plane checked out, local shops =
can't spin the unit because of the fragile coupling so I put it on a =
drill and only got 8v.    Out of warranty, I ordered a new one and =
decided this morning to look inside as these things are fairly standard. =
  Field (rotor) windings were fine and amps checked out.   Diodes all =
checked out.  Stators never have a problem?   When the cover was =
removed, the stator has three windings and a common terminal.  Two of =
three stator leads were broken off  and the the third tested open =
somewhere and is not repairable.  I also found the rear bearing spinning =
in the case which isn't great because the bearing seems fine and it =
should have been a good press fit or otherwise firmly attached.  The =
brushes are in good shape as is the rotor and drive bearing and =
coupling.

Vibration could be the culprit and this engine has had shakes for a =
while. Maybe this unit is part of the problem?  Fortunately, they are =
not horribly expensive but as I spoke to Bill at B&C he had hoped to see =
1700 hour life but this has multiple problems that would never make it =
that far.   The failure mode on these stator wires suggests a problem so =
if your SD-20 fails or is intermittent, you can easily check these 4 =
wires for continuity.  While I am not advising changing any parts, the =
diode packs, bearings and rear case parts are fairly easy to source.  =
B&C makes STCd units so parts out the door is not permitted.    Repairs =
on this unit would equal the cost of a new unit according to B&C which =
is too bad because a reasonable repair/overhaul is a good business model =
versus buy new.  Photo one shows the stator with the common (three leads =
together) and only two of the three coil leads showing.  The third broke =
off, one is open circuit and one is broken at the screw in the next =
photo.  The second photo shows two of the stator wires that are screwed =
to the diode pack.  One broken at the stator level and one broken at the =
screw itself.   If anyone has a core, I'll pay shipping, get a bearing =
and put this on the shelf as a spare. Thanks, Paul, Legacy, Spruce =
Creek.
<IMG_0051.jpeg><IMG_0050.jpeg>--
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