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Setting and Checking the Replacement Potentiometer
1. Rotate the bare potentiometer shaft to its maximum counterclockwise position . Slip the black knob onto the shaft .
Line up the pointer with the end of the sample frequency scale on the [+] side . Tighten the two set screws on the
knob .
2. Rotate the knob from minimum to maximum setting to make sure it moves smoothly .
On/Off Switch
If switch becomes undependable or fails completely, it must be replaced . Replacement switches, complete with all
necessary wire leads and terminals, are available from Sentry Equipment Corp .
1. Disconnect all power to the sampler controller . Remove the rubber seal hex nut from the toggle on the outside of
the controller . Release two set screws on the controller knob and remove the knob . Remove the rubber seal nut on
the potentiometer shaft .
2. Open the sampler controller . Remove the subplate holding switch, autofuse and potentiometer . Remove the hex
nut holding the switch to the subplate .
3. Disconnect the two switch leads from the spade terminals . Remove the switch .
4. Insert the replacement switch and reassemble in reverse order .
Pneumatic Components
Replace either the air pressure regulator or the solenoid air valve using the following steps:
1. Disconnect the air line tubing to the sampler . Disconnect the incoming compressed air supply line . Open the
sampler controller enclosure . Disconnect the wire leads between the cover and box . Completely remove the cover
to a safe, clean area .
2. Lift the clear plastic vent tube into the sampler controller box . Using a 1/2-inch open end wrench, unscrew the hex
nut at the top of the valve coil . (Note that the tubing will contact the back wall, but by folding it over, the nut can
be removed) . This will release the valve coil from the valve body .
3. Remove the large aluminum locking ring that holds the air regulator in place . Carefully loosen it with pliers . The
regulator and lower valve body can be removed from the bottom of the enclosure . Further disassembly now can
be done as required
4. Remove the DC solenoid coil by disconnecting the two spade terminal lead wires and pressing the coil up out of
the grommet . The coil may be tested with an ohmmeter . A good coil will have about 20 ohms resistance . A much
higher resistance indicates an open or burned-out coil, while a much lower resistance indicates a shorted coil .
5. Replace the malfunctioning component and reassemble in reverse order of above steps . Refer to the circuit
diagram for reconnection of solenoid lead wires . Refer to the air pressure regulator adjustment section of this
manual for adjustment of the air pressure regulator .
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Sentry Equipment Corp
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