Flowserve Logix 3400MD User Instructions page 41

automatically moves the position feedback assembly to its limit in the
unlikely event of failure of any component in the linkage.
Stem Position Sensor Replacement
To replace the stem position sensor, refer to Figure 16, 19 and 22 and
proceed as outlined below. The following tools are required:
• Phillips screwdriver
0 WARNING: Observe precautions for handling electrostatically
sensitive devices.
1. Make sure the valve is bypassed or in a safe condition.
2. Disconnect the power and air supply to the unit.
3. Remove the main cover.
4. Remove the plastic board cover by removing the three retaining
screws (see Figure 16).
5. Disconnect the position sensor wires from the main PCB assembly.
6. Remove the two rotary position sensor-retaining screws and lift the
sensor out of the housing.
7. Turn the new position sensor shaft until the dot on the side of the
shaft is aligned with the wires on the side of the position sensor
(Figure 19).
8. Insert the position sensor into the shaft with the wires pointing
toward the main PCB assembly. Turn the position sensor clockwise
until bolting slots align with the housing screw holes and the wires
on the sensor protrude over the main PCB assembly.
NOTE: Do not mix the position sensor with those from older Logix
positioners. Older models contain sensors with different ranges that
will not work in the Logix 3400MD model. The wires on the Logix
3400MD position sensor are red, white and black.
9. Carefully center the position sensor on the shaft bore, insert and
tighten the screws. Do not overtighten.
10. Route the wires along the side of the position sensor and reconnect
to the main PCB assembly.
11. Install the plastic board cover. Insert the three retaining screws
through the plastic cover into the threaded boss and tighten evenly,
using a Phillips screwdriver. Do not overtighten (see Figure 16).
12. Reinstall all covers.
13. Reconnect power and air supply to the positioner and perform a
stroke calibration.
Logix 3400MD Digital Positioner FCD LGENIM3404-00 – 9/09
8.7 Main PCB Assembly
The main printed circuit board (PCB) assembly contains the circuit
boards and processors that perform control functions of the positioner.
The main PCB is to be replaced as a unit. None of the components on
the main PCB are serviceable. It consists of a controller board and a
Fieldbus communication board.
Replacing Main PCB Assembly
To replace the main PCB assembly, refer to Figure 12 and 16 and
proceed as outlined below. The following tools are required:
• Phillips screwdriver
0 WARNING: Observe precautions for handling electrostatically
sensitive devices.
1. Make sure the valve is bypassed or in a safe condition.
2. Disconnect the power and air supply to the unit.
3. Remove the main cover.
4. Remove the plastic board cover by removing the three retaining
screws (see Figure 16).
5. Remove the retaining screw from the main PCB assembly.
6. Remove the five wire connections from the main PCB assembly and
lift the main PCB out of the housing (see Figure 16).
7. Reinstall the five wire connections (see Figure 12) on the new main
PCB.
8. Install the new main PCB into the housing. Insert the retaining
screw through the board into the threaded boss and tighten, using
a Phillips screwdriver. Do not over tighten.
9. Install the plastic board cover. Insert the three retaining screws
through the plastic cover into the threaded boss and tighten evenly,
using a Phillips screwdriver. Do not overtighten (see Figure 16).
10. Reinstall all covers.
11. Reconnect power and air supply to the positioner and reconfigure
the positioner being sure to perform a stroke calibration.
8.8 Pressure Sensor Board
On advanced model Logix 3400MD positioners, a pressure sensor
board is installed in the positioner. The pressure sensor board contains
two pressure sensors that measure the pressure on output ports 1
and 2. The main PCB electronics automatically senses the presence of
the pressure sensor board. If present, the actuator pressure sensors
are used in the positioner control algorithm to enhance valve stability.
For optimal performance, the actuator pressure sensors need to be
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