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On IBC877/78 relays, set the relay on the
the contacts are just open.
close as possible to 2.0 aolps. Then movethetilne dial to the No. 10 position and check
the current required to just move the disk away fran the stop arm.
be within the limits 1.88 to 2.12
that movement is not over one-half inch, measured along the periphery of the disk.
This is calied a ccmpensation check.
limits,
the following steps should be taken:
caapensation at No. 10 time dial is within limits.
Recheck compensation after the resistor adjustment.
the resistor.
DIRECTIONAL UNIT .
Bearings
The lower jewel bearing should be screwed all the way in until its head engages the
end of the threaded core support.
To check the clearance between the iron core and the inside of the rotor cup, press
down on the contact arm near the shaft, thus depressing the spring-mounted jewel until
the cup strikes the iron.
Cup and Stator
Should it be necessary to remove the cup-type rotor fron the directional unit, the
following procedure should be followed:
All leads to the unit should first be disconnected and tagged for identification in
reconnecting.
The unit can then be removed from the cradle with its mounting plate
still attached.
The upper of the three flat-head screws holding the unit to the plate should now be
On some models, it may be necessary to remove a resistor or capacitor to
removed.
expose this screw. The four corner screws clamping the unit together, should next be
removed, and the entire top structure lifted off.
assembly and exposes the stator assembly, which should be protected to keep it from
dust and metallic particles until the unit is reassembled.
To remove the shaft and rotor frcm the contact head assembly, the spring clip at the
top of the shaft must be pulled out and the clutch adjusting screw taken out of the side
of the molded contact arm.
rotor must be handled very carefully while it is out of the unit.
Contact Adjustments
To make contact adjustments, refer to Fig. 20 for identification of low gradient
l
contact parts and proceed as follows:
*Indicates Revision
Adjust pickup within the limits 1.96 to 2.84
If the disk moves at the lower limit, check
If the current falls outside the1.88 to 2.12 amp
The upper bearing should be adjusted to allow about
The shaft should move about l/16 inch.
The shaft and cup can now be pulled out of themolding. The
21
amp tap with the time dial set so that
This current should
reset the control spring until
Then restore pickup by adjusting
This gives access to the cup
but as
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