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Page Title:
Procedure Steps in Troubleshooting |
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  TM 11-6130-38-34
3-8. Procedure Steps in Troubleshooting
3-11. A1 Board Test
Examine
each
circuit
board
and
module
for
loose
or
3
through
terminals
8
with
a. M o n i t o r
broken
components,
foreign
materials,
etc.
Check
oscilloscope
for
square
wave
of
approximately
3.5
v
peak
at
6.2
kHz.
If
signals
are
not
present,
repair
wire
terminations
for
breakage
or
loose
soldering.
The
red
wire
to
pin
7
of
each
power
switch
board
before
proceeding.
See
sequence
4.
(A7),
inductor
L901,
and
the
primary
of
the
output
b.
Monitor
terminals
10
through
15
with
oscilloscope
for
a
400-Hz
sine
wave
of
approximately
transformer
(T1)
should
be
disconnected
at
this
1. 2
peak
to
peak.
If
signals
are
not
present,
repair
time.
V
before
proceeding.
See
sequence
5.
3-9. Ohmmeter Tests
c. W h e n
all
the
above
conditions
have
been
met,
a. Measure
dc
input
leads
with
ohmmeter.
The
remove
power
and
connect
L901
to
terminals
34
and
correct
polarity
should
measure
greater
than
350
35
of
A4
board.
Connect
oscilloscope
or
dc
voltmeter
ohms.
See
between
terminal
35
(+8
to
12v)
of
A4
board
and
2
b. R e v e r s e
polarity
should
measure
low
resistance
(GND)
of
A4
board.
Increase
input
voltage
to
+
15
v
(but
greater
than
1
ohm).
This
is
measured
at
for-
while
observing
the
+
8
to
12
v
monitor.
If
the
ward
impedance
(Z)
of
CR501
(A5).
observed
voltage
exceeds
+
13
v,
repair
regulator
c. Disconnect
J503,
measure
resistance
of
T501,
circuit
before
proceeding.
See
sequence
6.
T502,
and
T503
secondary
windings
(center
tap
to
d. Continue
increasing
input
voltage
to
+
28
vdc
each
side).
Resistance
should
be
approximately
25
+8
to
12
v
monitor.
Regulator
while
observing
ohms
on
each
side.
If
not,
replace
filter
module
(A5).
should
maintain
8
±
1V a t
output.
If
not
correct,
Reconnect
J503.
repair
before
proceeding.
See
sequence
6.
d. Measure
power
transistors
(Q703,
Q704,
Q708,
e. Monitor
pins
17
through
21
on
the
A
1
board
for
Q709,
Q710,
Q711)
for
case
to
heatsink
shorts.
These
an
approximately
15
v.
400
Hz
square
wave
output.
If
measurements
are
made
on
the
A7
module.
signals
are
not
present,
repair
before
proceeding.
See
3-10. Power Applied Tests
3-7,
sequence
7.
CAUTION
3-12. Phase Adjustments Al Board
Position
all
loose
wires
so
that
they
will
not
NOTE
come
in
contact
with
conductive
elements.
This
procedure
is
applicable
only
when
T101
-
Check
to
see
that
the
red
wire
to
pin
7
of
each
3
or
associated
components
have
been
power
switch
board
(A7),
inductor
L901
and
changed.
the
primary
of
the
output
transformer
(T1)
is
a. For
phase
A,
connect
capacitance
decade
box
in
disconnected.
parallel
with
T101
terminals
1
and
2.
a.
Test
Equipment
Setup.
(1)
Monitor
T101
terminal
1
and
U105
pin
5
(at
(1) Connect
decade
resistance
box
(set
at
820
R106)
with
dual
trace
oscilloscope.
ohms)
in
place
of
R442
cm
A4
board.
(2)
Adjust
decade
box
capacitance
until
the
(2)
Connect
oscilloscope
or
dc
voltmeter
be-
square
wave
at
U105
is
in
phase
with
sine
wave
at
tween
terminals
1
(+5v)
and
2
(GND)
of
A1
board.
T101
(±
4.0°
maximum
deviation).
(3)
Connect
oscilloscope
or
dc
voltmeter
be-
(3)
Select
capacitors
C110
and
C113
to
equal
the
tween
terminals
9
(
2.
5
v
reference)
and
2
(GND)
of
A1
value
indicated
by
the
decade
box.
board.
b. For
phase
B
select
C111
and
C114
as
in
A
phase
(4)
Connect
dc
power
source
to
input
connector
above,
using
test
points
applicable
to
phase
B.
For
J1.
phase
C,
select
C112
and
C115
as
in
A
phase
above
b.
Power
Tests.
using
test
points
applicable
to
phase
C.
(1) W h i l e
monitoring
dc
input
current,
slowly
3-13. A2 Board Test
increase
input
voltage
to
+
5
v.
If
input
current
does
not
exceed
1
amp,
continue
increasing
input
voltage
For
A
phase
data
output,
monitor
board
terminals
15
and
17
with
dual
trace
oscilloscope
for
groups
of
to
+
8
while
observing
+
5
monitor.
The
+
5
V
V
V
15,
a
+
5
level
with
4
negative-going
pulses
at
a
regulator
circuit
on
the
A4
board
should
be
5
v
±
.5.
V
V
400-Hz
group
repetition
rate.
The
signal
at
terminal
If
output
is
incorrect,
repair
same
before
proceeding.
15
should
occur
180°
out
of
phase
with
that
at
See
3-7,
sequence
1.
terminal
17.
If
signals
are
not
present,
repair
before
(2)
Monitor
2
.5
v
reference
voltage
at
terminal
9
proceeding.
See
sequence
8.
of
A1
board
for
2.5
v
±
0.25.
If
output
is
incorrect,
repair
before
proceeding.
See
sequence
2.
3-14. A3 Board Test
(3)
If
5
and
2
.5
v
regulators
appear
to
function
For
C
phase
data
output,
monitor
terminals
13
and
6
properly,
increase
input
voltage
to
28
vdc.
If
input
as
in
A
phase
3-13).
For
B
phase
data
ouput,
current
exceeds
2
amperes,
locate
and
repair
fault.
See
3-7,
sequence
3.
3-15
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