4. Parts Replacement
A. Minor electrical components
(1) Lamps and fuses are mortality type items which require simple periodic replacement.
(2) Switches, meters, contactors and fan motor in the power supply fall into the category of parts
which can be expected to fail at infrequent, irregular intervals. Instructions for repair and replace-
ment of these parts are obvious. Be certain the input power is turned off. Obtain the replacement
part specified in the parts list. Replace the part by substituting the new part for the old taking care
not to mix up the leads. See Sections 2 and 3.
(3) The user-supplied disconnecting means must be of proper capacity for the rated input voltage.
See the rating for your input as listed for your use in 1-2, Figure 1, recommended wire size table.
Be certain your specification number is designed for your input voltage. No visible inspection is
possible, except for the marked rating if the input power source is off. The use of the wrong input
voltage could be the cause for equipment damage.
B. Major Electrical Components
(1) Major electrical components such as the power transformer, filter choke, and SCR devices on
the SCR heat sink assembly should be replaced or repaired at an overhaul type facility.
(2) The firing circuit board can be easily replaced as a “plug-in” assembly. Minor calibration adjust-
ment may be required for optimum performance. It is recommended, however, that this adjust-
ment be made only by factory authorized personnel.
(3) The flyback rectifier diode located on the main SCR heat sink assembly rarely fails from nor-
mal use. If replacement is ever required, be sure to connect the replacement exactly as the origi-
nal after torque wrench tightening the nut to the stud at 4.2 to 5.2 foot pounds
(5.70 to 7.05
newton meters).
(4) SCR device replacement requires extreme care, special tools, and the exact replacement part
and technique for optimum performance. The replacement of the SCR should be done at the fac-
tory or an authorized repair facility. A replacement SCR bridge subassembly can be obtained
from the factory which would allow the customer to install so long as he was certain to exactly re-
place all leads and components in the same position with the same hardware. This task would
still require considerable care and time.
OM-2010
3-1 April 10/89 Revised
Page 2
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