Mooney M20K - Page 98

MOONEY
AIRCRAFT
CORPORAT1ON
M20K
SERVICE
AND
MAINTENANCE
MANUAL
83
;;z
i9
thus
reducing
Ule
delaylo
approdmately
2
seconds.
In
B
3
order to
calibrate
the
law
fuel
channel
the
set
point,
a
R51,
is
adjusted
with
the
screwdriver
adjustment
I%
f
accessible
through
the
front
of the
annunciator
while
there
is
a
preset
number
of
gallons
in the
tank.
The
time
delay
must
be
removed
from
the
circuit
by
moving
S3,
accessible
through
the
front
of
the
annunciator,
4
from
the
NORMAL
position
to
the
CALIBRATE
ae
i‘9 I
f
~r
position.
This
opens
the
retum
for
capacitor
C9
and
the
indication on
the
L
LOW
FUEL
channel
will
not
be
delayed.
After
calibration
is
accomplished,
restore
the
time
delay
by
moving
S3
from
the
CALIBRATE
position
back
to
the
NORMAL
positio?.
The
position
S3
can
be
determined
without
removing
the
front
of
the
annunciator.
When
the
TEST
switch
is
depressed
observe
the
indication
of
L
LOW
FUEL
and R
LOW
kt
~I I P
~g
FUEL.
With
S3
in the
NORMAL
position
there
is
a
delay
of
approximately
2
seconds
in
illumination,
but
pa
1 9 1~ B~
with
S3
in the
CALIBRATE
position
there
is
no
delay
in
annunciate
low
fuel
are
the
same
circuits
that
have
been
used for
many
years
in
IAI
annunciators
used
on
Mooney
aircraft.
The
method
of
dimming
however,
has
sr
I 1 s~i
s~
been
changed
and
e>cpanded
from
what
i~as
been
used
in the
past.
In
the
past
only
the
low
fuel
channels
dimmed,
excluding
GEAR
DOWN
discussed
above,
while
now
the
dimming
has
been
e~panded
to
include
X
additional
5
channels.
From
the
perspective
of the
pilot
cic
~x
5
the
operation
is the
same,
depress
the
DIM
switch
and
active
channels
dim,
depress
the
TEST
switch
and
active
dimmed
channels
return
to
bright.
When a
I~
dimmed
channel
is
e>dingu~hed
and
then
reactivates
it
will
reactivate
bright.
The
method
to
accomplish
this,
however,
is
considerably
different
from
the
past.
Each
s~
eb
channel
to
be
dimmed
is
driven
by
a
transistor,
in
this
g
case
08
which
returns
the
lamp
to
ground
through
two
parallel
paths.
The
path
to
provide
a
dim
indication
is
np
through
resistor
R29
which
reduces
the
brilliance
of the
lamp.
In
the
bright
mode
R29
is
shorted
by
06
and
nH
g
,a
CR13
which
provide
a
low
impedance
path
to
ground.
oX
Transistor
06
is
controlled
in
condudion
by
a
latch
95
composed
of U3
and
as
associated
resistors
R22,
R23,
a
R24,
R25,
R26
and
R27
as
well
as
the
signals
DIMBIAS
and
DIMIN3.
If
the
channel
is
active
DIMIN3
will
be
near
ground
and
with
DIMBIAS
near
3
VDC,
the
output
of Us
will
be
high,
thus
dn’ving
Q6
into
conduction.
When
the
DIM
Switch
is
depressed
2~Xn
momentan’ly
DIMBIAS
goes
high
to
12
VDC
and
U3
I
f
switches
its
output
low
and
latches
through
R26.
This
low
output
removes
the
dn’ve
from
06
and
DS3
dims.
When
the
TEST
Switch
is
depressed
momentarily,
DIMBIAS
goes
low
and
U3
switches
its
output
high,
conducts
and
drives
08
into
saturation
to
light
the
L
latches
through
R26,
and
drives
06
into
conduction.
LOW FUEL
channel
lamp,
DS3.
The
Q10
08
network
When
the
channel
deactivates,
08
opens
the
return
to
is
required
to
provide
the
transition
between
the
internal
ground
and
DIMIN3
rises
which
returns
latch
U3
to
a
12
VDC
and
aircraft
+28
VDC.
The
delay
provided
by
high output
state.
the
charge
of C9
through
R48
and
R49
provides
filtering
to
preclude
false
annunciation
in
rough
air.
6´•0
HULOVAC
When
the fuel
level
rises,
due
to
sloshing
in
the
tank
Th,
Highnow
Vacuum
circuits
are
shown
in
Figure
5.
and
U5:C
switches
to
a
low
output
state,
C9
is
This
channel
is
designed
to
accept
two
+28
VDC
discharged
rapidly
through
R49.
The
delay
time
of
the
signals,
one
from
a
low
vacuum
sensor
and
one
from
a
char~ing
network
provides
a
delay
In
low
fuel
high
vacuum
sensor.
~hen
low
vacuum
is
detected
the
annuncfation
of
approximately
20
seconds.
A
test
of
the
annunciator
will
flash
and
when
high
vacuum
is
functioning
of the
low
fuel
channel
is
accomplished
by
detected
the
annunciator
will
illuminate
steady.
A
+28.
applying
TEST+
through
R43
CR18
to
the
input
of
VDC
signal
applied
to
LOW
VAC
INPUT
will
drive
Qi?
U5:C
to
switch
U5:C
and
applying
TEST+
through
R42
into
conduction
through
the
bias
network
R56,
R57,
CR?5
to
accelerate
the
charging
rate
of
the
filter
C9,
CR17,
and
CR22,
thus
illuminating
DS9.
24-39-06
20
ALSO SEE
FIGURE
AS
HORIZONTAL
(NE~IflC)
OLDWILLWAYNE