Instruction Manual
D101728X012
3710 and 3720 Positioners
September 2017
42
5.
Before tightening the machine screws holding the spool valve, make sure the end of the summing beam does not
contact the spool.
Rather, the summing beam should contact the
spool head
. If necessary, adjust the position of
the spool valve on top of the action block, making sure the summing beam does not bind on the spool throughout
the full travel of the summing beam. Tighten the two machine screws.
6. Be sure the spool head and summing beam remain engaged, but do not bind up, over the entire operating range of
the input module.
Assembling the Feedback Shaft (CamShaft)
1. Inspect the feedback shaft (key 38). Be sure the shaft is free from any damage. Inspect the flanged bearings (key 17)
and spacer (key 69). Replace, if necessary.
2. Properly install the flanged bearings in the positioner base plate. Install the spacer on the feedback shaft. Insert the
shaft with spacer through the bearings and base plate. Make sure the feedback shaft rotates freely.
3. Install the washer (key 39) and retaining ring (e‐clip) (key 40) that hold the feedback shaft in place.
4. Attach the cam (key 36) and cam locknut (key 37).
5. Set the initial cam position following the procedures given in this manual, if necessary.
Replacing the Feedback Arm Assembly and Span Adjuster Assembly
Note
The zero adjustment locknut and zero adjustment knob are identical parts, key 35.
Note
To identify the span adjuster assembly for 0.4 to 2.0 bar (6 to 30 psig) input range, red color coding appears on the range spring.
1. Make sure the zero adjustment knob (key 35) is installed on the span adjustment shaft (threaded rod) before
installation into the zero adjustment pivot. Install the span adjustment assembly by sliding the threaded rod
through the zero adjustment pivot on the feedback arm. Install the zero adjuster locknut on the threaded rod.
2. Install the cam roller (key 23) and shoulder screw (key 24). Be sure the cam roller rotates freely.
3. Place the flanged bearing (key 22) and feedback arm assembly on the feedback pivot. Place the washer (key 26) on
the pivot and install the retaining ring (e‐clip) (key 27) to secure the feedback arm on the feedback pivot.
4. If necessary, attach the cam (key 36) and cam locknut (key 37) to the feedback shaft.
5. Perform the calibration procedures in this manual.
3722 Converter Maintenance
Replacing the Converter Primary O‐Ring and Filter
Key numbers used in this procedure are shown in figure 32.
1. Locate and remove the nozzle restriction adaptor assembly (key 75).
2. Inspect and replace, if necessary, the O‐rings (keys 76 and 77). Apply lubricant (key 82) to the O‐ring before
replacing.
3. Inspect and replace the filter cartridge (key 88).