Curtis PMC 1209B/1221B/1221C/1231C Manual
26
MAINTENANCE & ADJUSTMENT
2. If adjustment is required, loosen the screw holding the lever on the pot
shaft. Use a screwdriver to rotate the pot shaft slightly with respect to
the lever. Recheck the point at which the resistance starts to increase
and continue making adjustments until the increase starts at 3 mm
(1/8") [at 1.5 mm (1/16") for potboxes without the microswitch].
When adjustment is correct, tighten the screw holding the lever on the
pot shaft, then recheck to see that this action did not disturb the
adjustment. Make sure that the lever is still seated down on the pot shaft
below the slight bevel on the end of the shaft.
3. Check the resistance with the lever pushed all the way to the other stop.
It should be between 4500 and 5500 ohms. If it is outside this range,
the potbox is faulty and should be replaced.
4. For potboxes equipped with a microswitch, check for correct switch
operation. Use an ohmmeter, or simply listen for the slight click the
switch makes. It should operate when the lever is 1.5 mm (1/16") from
the return stop. If it does not, adjust by loosening the two screws
holding the slotted microswitch mounting plate to the stop spacers and
moving the plate. Recheck the switch operating point after tightening
the screws.
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