Raytheon Beech Baron E55 - Page 688

Raytheon
Aircraft
Company
BARON
55
AND 58
SHOP MANUAL
TRIGGER
CIRCUIT
TROUBLESHOOTING
a.
Using
a
high
impedance
voltmeter,
check for
180
vdc
at
the
junction
of
R8,
R9
and
C5. If
there
is
no
voltage,
check
C5
and
SCR
T1145A2.
b.
If
there
is
voltage
at
the
junction,
it should
periodically
drop
to
around
30
volts
as
the
SCR
triggers.
if
the
SCR
does
not
trigger,
measure
the
voltage
across
R7
(100
ohms).
This
voltage
will
be
below
0.5
volts.
If
the
voltage
is
indicated,
place
an
oscilloscope
across
R7 and
look
for
a
positive going
pulse
of around
4 volts
at
the
repetition
rate
of
40
to
55
times
per
minute.
If
the
pulse
is
recorded
on
the
scope,
then
the
SCR
is
not
triggering
and
should
be
replaced.
c.
When
no
voltage
is
observed
across
R7,
check for
battery
voltage
at
R5 and R6.
if
voltage
is
present,
then
the
trouble is
in
the
unijunction.
d.
If normal
voltage
is
observed
across
R7,
check the
capacitor
04
for shorts
and
leakage.
e.
If
unijunction
03
is
to
be
replaced,
it
may
be
necessary
to
readjust
the
flash rate.
This
can
be
done
by
changing
R5
or
by
changing
the
value
of
04.
In
many
cases,
the
value
is recorded
on
the
component
board,
and
it is
only
necessary
to
order the
exact
value from the
manufacturer
(see
the
Vendor
Publication
List).
NOTE:
In
some
instances,
power
supply
units
which have
been stored
or
not
operated
on
the
aircraft
for
a
considerable
period
of
time,
may
not
operate
instantly
when
the
system
is
tumed
on.
Before
determining
that
the
power
unit
is
inoperative,
leave the
system
on
for
a
period
of
at
least
30
minutes.
If
the
power
unit
does
not
operate
in
this
span
of
time,
refer
to
TROUBLESHOOTING
POWER
UNIT.
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(2)
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Bullock Power
Supply
Schematic
(Internal)
Figure
7
E21
SECTION
13
Dec
31/03Page
91