E. Contactors
(1) Output Contactor, K2
The output contactor has contacts that can be visually inspected whenever the input power is re-
moved from the power supply. If the contacts are badly burned the contactor should be replaced
as soon as possible. Slightly pitted and burned contacts can be cleaned up with a commercial
contact cleaner and very fine grained emery cloth or equivalent. If application of 28 V DC to the
coil of the K2 contactor does not make the normally open contacts close completely or the nor-
mally open contacts open completely, the contactor should be replaced if the contact mechanism
can’t be mechanically adjusted for proper operation.
(2) Input Contactor, K1
If input power has been turned off at the source of power, the K1 input contactor contacts can be
visually inspected by removing the two screws holding the contact cover in place. If the contacts
are badly eroded, burned, or stuck, the replacement contacts and spring for each pole can be or-
dered with the number given in the applicable replacement parts list. If the contactor with DS1
light on has failed to pick up before the inspection, and no mechanical obstruction has been
found, the contactor should be replaced or repaired with the replacement coil and contacts speci-
fied in the parts list. Many customers prefer to replace the whole contactor, especially for the con-
dition showing bad coil and contacts. If DS1 light is good but does not glow and the F8 fuse
checks good, the problem is in the control transformer circuit.
F. Control Transformer
The control transformer is located on the rear of the lifting baffle. The F8 fuse
(.5A)
is normally
mounted on top of the control transformer. The voltage input connection on the control transformer
must also be changed whenever the input voltage changes.
Not changing the input connection when going from a lower to higher input voltage will result in a
burned out control transformer. The same result occurs if a larger than 1/2 ampere fuse is substituted
for F8, especially if the input contactor is faulty. The only sure way for checking the control trans-
former to verify what the input voltage and output voltages are. If there is no proper output with proper
input voltage, replace the control transformer.
4. Major Components Check and Repair
A. Main Power Transformer
No replacement parts are available for the main transformer. The replacment power transformer part
number for your specification number is given in the replacement parts list in Chapter 4. This part and
most of the major component parts can best be replaced at the factory or a factory authorized repair
facility. However, replacement can be done by the customer if he exercises care to reconnect every-
thing to the same points and in the same manner as the original part.
WARNING: HIGH VOLTAGE - ELECTRIC SHOCK CAN KILL! TURN THE
SOURCE OF INPUT POWER OFF WHEN CHECKING THESE CONNECTIONS.
BE CERTAIN CAPACITORS ARE DISCHARGED BEFORE TOUCHING THE
CIRCUITRY.
OM-2010
3-2 April 10/89 Revised
Page 4
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