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E. Troubleshooting
TROUBLE
No load movement
Load movement in only one
y
direction
di
ti
Movement of load in both
directions, but maximum load
di
ti
b t
i
l
movement obtainable in only one
direction.
Erratic load movement
PROBABLE CAUSE
Insufficient control pressure or supply
pressure.
Improper or poor electrical connections.
Flow ports blocked.
Servo valve mounting bolts too tight.
Amplifier or signal source inoperative.
Torque motor inoperative.
Pilot spool not centered.
One torque motor coil inoperative.
Improper or poor electrical conditions.
Insufficient control pressure.
Flow ports blocked.
Pilot spool not centered.
d
Amplifier or signal source null shift.
Main sleeve too far out of adjustment.
Contamination.
REMEDY
Check the control pressure or supply
pressure – the gage installation should be
close to the servo valve.
With the amplifier or signal source turned
off, check continuity with an ohmmeter for
cold solder joints on the electrical
connectors, broken leads and for improper
pin wiring.
Check for proper manifolding (O-rings) and
for obstructions or improper piping of the
hydraulic lines.
Loosen the four servo valve mounting bolts
and adjust to the values specified in
Section VI – Overhaul.
Install milliammeters between the torque
motor and amplifier or signal source, one in
series with line "A" and the other in series
with line "D", and check for the proper dif-
ferential currents.
With the amplifier or signal source turned
off, check the torque motor coils for either
an open or shorted condition by placing an
ohmmeter across pins "A" and "B" of the
electrical connector for one coil and across
pins "C" and "D" for the other.
Recenter pilot spool. Refer to page 8.
With the amplifier or signal source turned
off, check the torque motor coils for either
an open or shorted condition by placing an
ohmmeter across pins "A" and "B" of the
electrical connector for one coil and across
pins "C" and "D" for the other.
Install milliammeters between the torque
motor and amplifier or signal source, one in
series with line "A" and the other in series
with line "D", and check for the proper dif-
ferential currents.
Check the control pressure – the gage
installation should be close to the servo
valve.
Check for proper manifolding (O-rings) and
for obstructions or improper piping of the
hydraulic lines.
Recenter pilot spool. Refer to page 8.
Install milliammeters between the torque
motor and amplifier or signal source, one in
series with line "A" and the other in series
with line "D", and check for the proper dif-
ferential currents. Refer to operating
characteristics.
Refer to spool centering adjustment page
8 then null adjustment page 7.
Install the proper filter required. Clean the
system components, and thoroughly flush
the system.
9
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