Potential Trouble
Servovalve does not follow input command
signal. (Actuator or components are
stationary or creeping slowly).
High threshold. (Jerky, possible oscillatory
or “hunting” motion in closed loop system).
Poor response. (Servovalve output lags
electrical command signal).
High Null Bias, (High input current
required to maintain hydraulic cylinder or
motor stationary).
Probable Cause
1. Plugged filter element.
1. Plugged filter element.
1. Partially plugged filter element.
1. Incorrect null adjustment.
2. Partially plugged filter element.
Remedy
1. Replace filter element.
1. Replace filter element.
1. Replace filter element.
Check for dirty hydraulic fluid in system.
1. Readjust null.
2. Replace filter element and check for
dirty hydraulic fluid in system.
8. TROUBLESHOOTING CHART
The following troubleshooting chart lists potential troubles encountered, probable causes and remedies.
Table 1. Replacement Parts
Part Description
Qty.
Part Number
G761/761 Series Filter Replacement Kit 1
B52555RK201K001
O-Ring (1)
2
-42082-003
O-Ring (1)
2
G2141-013-015
Filter Disc (1)
1
A67999-065
Base O-Rings
4
-42082-022
1
-42082-013
(1) Included in Filter Replacement Kit
9. FILTER ASSEMBLY REPLACEMENT
Tools and Equipment
a. 3mm
Allen wrench
b. Torque wrench
a.
Remove the four socket head cap screws with 3mm Allen wrench.
b.
Remove the filter retainer.
c.
Remove and discard the filter disc.
d.
Remove and replace the o-ring on the filter retainer and the o-ring in
the filter bore.
e.
Reinstall in reverse order, torque screws to 35-40 in-lbs.
10. FUNCTIONAL CHECKOUT AND CENTERING
a. Install servovalve on hydraulic system or test fixture, but do not connect
electrical lead.
b. Apply required system pressure to servovalve and visually examine for evi-
dence of external leakage. If leakage is present and cannot be rectified by
replacing o-rings, remove the discrepant component and return for
repair or replacement.
Note: If the system components are drifting or hardover, adjust
the mechanical null of the servovalve.
c. Connect electrical lead to servovalve and check phasing in accordance
with system requirements.
11. AUTHORIZED REPAIR FACILITIES
Moog does not authorize any facilities other than Moog or Moog
subsidiaries to repair its servovalves. It is recommended you contact Moog
at (716) 652-2000 to locate your nearest Moog repair facility. Repair by an
independent (unauthorized) repair house will result in voiding the Moog
warranty and could lead to performance degradation or safety problems.
Figure 5
Socket Head
Cap Screw
2X O-Ring
P/N -42082-003
Filter Retainer
Filter
P/N A67999-065
2X O-Ring P/N G2141-013-015
