Mooney M20K - Page 97

SERVICE
AND
MAINTENANCE
MANUAL
M20K
MOONC/
AIRCRAFT
CORPORATION
With
both
the
Dim
Switch
and Test
Switch
relaxed,
Lights
are
on,
however,
CH1RET
is
also
+28
VDC
and
transistor
Q3
is
in
saturation
and 02
is
off,
giving
CR9
switches
this
return
path
off,
the
retum
path
for
the
DIMBIAS
a
value
of
approximately
9
VDC.
When
the
GEAR
DOWN
lamp
being
through
Ri5
to
Ground
and
Dim
Switch
is
depressed
03
comes
out
of
saturation
GEAR
DOWN
now
illuminates
at
reduced
brilliance.
and
DIMBIAS
n’ses
to
12
VDC,
and
when
the
Test
The
GEAR
UNSAFE
channel
accepts
+28
VDC,
Switch
is
depressed
02
saturates
and
DIMBIAS
drops
INPOS2,
through
isolation
diode
CRIO,
illuminates
at
to
near
0
VDC.
In
the
event
that
both
switches
are
full
brilliance
and
does
not
dim.
A
test
signal,
TEST+
is
depressed
simultaneously,
the
0
VDC
value
of
applied
to
both
GEAR
DOWN
and
GEAR
UNSAFE
DIMBIAS
will
prevail
and
the
dimmed
channels,
with
through
CR8
and
CR11
respectively.
the
exception
of
Channel
i,
are
reset
to
a
bright
condition.
3.0
FLASHER
CR7
In4ees
The
Flasher,
shown
in
Figure
2,
provides
the
circuit
to
i
rnPosi
flash
the
outputs
of
the
left
and
n’ght
alternator
warnings,
the
low
voltage
waming
and
the
low
vacuum
LI1PPOSI
warning.
The
flasher
consists
of
an
astable
oscillator
CR8
driving
an
NPN
common
emitter
connected
transistor,
DSI
Q4.
T711s
allows
the
open
collector
of
04,
identified as
73~7
FLASH,
to
sink
the
drive
from
the
output
amplifiers
of
the
appropn’ate
warning
channels.
CR9
CH1RET
POS1R
R1S
1BVDC
I
28UDC
jR13 I
331(
2.
21
R14
331
CRi(j
FLRS
~wceos
lnPOS2
1/4-11(33382
Ri2
U2
P4
4.
71
tnPPOS
CRI1
cNeeQS
2n3eisl I IPEST+
RS
CS
R10
j
I
-I
I I
FIGURE
3
tRNDlnG
GE~R
IWDICMORS
;214FD
331
i
331(
5.0
LEFT
AND
RIGHT
LOW
FUEL
BIGURE
Z
rtAsusR
The
Left
and
Right
Low
Fuel
circuits
are
shown
in
Figure
4.
The
left
and
the
right
channels
are similar,
and
only
the
left
channel
will
be
discussed
herein.
Signals
from
the
junction
of
the
left
and
n’ght
fuel
transducers
and
the
left
and
n’ght
fuel
quantity
gauges
are
applied,
respectively,
to
each
of the
inputs
INPOS3
4.0
LANDING
GEARINDICATORS
and
INPOS4.
This
signal
is
an
analog
signal
that
The
Landing
Gear
Indicators,
shown
in
F~ure
3,
indicates
the
quantity
of
fuel
measured,
the
typical
low
provide
the
status
of
the
landing
gear
position,
that
is,
fuel
point
being
on
the
order
of 0.1
volt.
The
low
fuel
whether
the
landing
gear
is
Down
or
not
and
whether
circuits
can,
however,
annunciate
an
input
up
to
the
landing gear
is
safe
or
unsafe,
unsafe
being
in
approximately
0.7
volt.
The
input,
INPOS3,
is
applied
transit.
The
circuit
shown
is
the
identical
circuit
that
has
through
an
isolation
resistor
R55
to
the
inverting
input
been
used
for
many
years
in
the
iAI
annunciators
used
of
open
collector
comparator
U5:C.
The
input
is
on
Mooney
aircraft.
The
GEAR
DOWN
channel
compared
with
the
set
point
effected
by
the
setting
of
dimmed
for
night
operation;
however,
in
the
interest
of
R51,
accessible
through
the
front
of the annunciator,
reliability,
the
dimming
circuit
is
separate
from
the
and,
when
the
input
is
less
than
the
set
point,
the
dimming
technique
used
on
the
other
dimmed
comparator’s
output
is
allowed
to
rise
by
means
of the
channels.
The
gear
down
signal,
+28
VDC,
is
applied
pull-up
resistor
R54
and
the
network
R48,
R49,
and
C9.
through
isolation
diode
CR7,
to
the
INPOS1
input
and
Feedback
res~tor
R53
provides
a
small
amount
of
CH1RET
is
returned
to
the
Nav
Light
bus.
Wnen
+28
hysterisis
to
preclude
oscillation
at
the
transition
point.
VDC
is
applied
to
INPOS1
and
the
Nav
Lights
are
off,
The
rising
output
of
U5:C
is
applied
to
the
the
Impedance
of
this
point
is
very
low
due
to
the
low
inverting
input
of
open
collector
comparator
U5:B
and
is
filament
resistance
of the
Nav
Light
bulbs,
and
GEAR
compared
with
a
reference
voltage
of
approximately
6
DOWN
illuminates
at
near
full
bn’lliance.
When
the Nav
VDC.
When
U5:B
switches
its
output
to
ground
QiO
24-39-06
19
OLDWILLWAYNE