Diode failure after approximately a 25
hour
"run-in" period is generally traceable
to
external
causes
such as lightning strike,
over
heating, reverse current fed into
the
unit, line voltage spikes,
etc
..
All
6
diodes are essentially in
the
same
circuit. When one
or
more diodes have been stressed
to
fuilure,
there
is no easy method
to
determine
how
badly stressed
the
remaining diodes may have been.
Therefore,
to
avoid possible continued failures and increased
down
time, it is recommended
practice
to
replace
the
entire assembly
rather
than
to
replace only
the
individual failed diodes.
If
the
rectifier
assembly is
to
be
repaired,
the
assembly must
be
removed from
the
unit.
Rotating
Rectifier
Assembly
Removal
and
Installation
Procedure.
As illustrated in
Figure
5,
the
rotating rectifier assembly consists
of
two
semi-circular sub-assemblies.
To
remove each
sub-
assembly, remove
the
three
exciter
rotor
lead flag terminals from
the
quick connect tenninals,
and
remove the
main
rotor
lead
from
the
main
rotor
tenninal post.
Remove
the
two
retaining
screws
from
each mounting board. After repair,
or
if
the
assemblies are
to
be
replaced, install each sub-assembly
in
the
same place
as
before.
Pay
particular attention
to
assure
that
the
white exciter
rotor
leads
are
installed on
the
sub-assembly having white diode leads, and
that
the
assembly having black
diode
leads receive
the
black exciter
rotor
leads.
Replacing
Diodes
on
the
Rectifier
Assembly. Prior
to
installing a replacement diode
on
the
heat
sink, sparingly apply a film
of
conductive heat sink compound around
the
base
of
the
diode
(do
not
coat
the
threads).
When
installing a diode
on
the
heat sink, care should
be
taken
not
to
over
torque
the
retaining nut
which
could
cause
damage
to
the
device.
Torque
to
28
to
30
pound-inches.
If
not
damaged,
the
existing
diode
lead
wire may
be
unsoldered from
the
failed diode, and resoldered
on
the
replacement.
RETURNED GOODS
Contact
Marathon
Electric
Manufacturing
Corporation
by telephone, fax,
or
letter
for
a
"Returned Material Authorization" (RMA) number before returning
component
parts
or
complete
units.
We
will
take
steps
to
return
your
unit
to
service quickly and
at
the
least expense possible.
At
the
same time,
we
will
analyze
the
cause
of
failure and, in
so
far as is possible, recommend steps
to
be
taken
to
prevent a recurrence
of
the
problem.
CAUTION
-
Single
bearing
generators
must
have
their
rotor
assembly
properly
secured
to
prevent
damage
during
transit
to
the
factory,
or
to
an
authorized
service
center.
15
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