Spark Gap Adjustment; Testing And Replacing Bridge Assembly Components - ESAB Heliarc 252 Instruction Manual

SECTION 4
4.1.4

Spark Gap Adjustment

Generally, the high frequency output of the unit increases as the gap setting
is increased. Electronic instability in other equipment may occur if the gap
is opened more than the factory-set .030 inches (+/- 002-in.). However, if the
high frequency intensity is not sufficient for your application; open or close the
spark gaps until the desired high frequency intensity is obtained. Remember
that high frequency radiation increases as the gap increases, and this can
cause interference in other electronic equipment.
1. Loosen retaining screw "A" only enough to free electrode point "C" for
adjustment.
2. Place feeler gauge of proper thickness between gap "B".
3. Apply slight pressure against loosened electrode point "C" so the feeler
gauge is held firmly in the gap. Tighten retaining screw "A".
Figure 4-1. Spark Gap Adjustment
4.1.5 Testing and Replacing Bridge Assy. Components
SCRs are devices which allow current to flow in only one direction and block
current in the other direction. The SCRs used in this power source are de-
signed to provide long trouble-free operation; however, should a failure occur,
they may require replacement. The testing procedures to determine defective
components are as follows:
1. Silicon Controlled Rectifier - Modules.
Disconnect the SCR wiring to break continuity and provide an open
circuit across the component to be tested. Using an ohmmeter set to
the R x 1 scale, check the resistance across the SCR in both direc-
tions. A good SCR will read high in both directions. If the reading is
low or zero in either direction, the SCR is defective.
When replacing defective SCRs, make sure the mounting surfaces
are clean. Make certain the polarity on the replacement SCR is the
same as on the unit being replaced.
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MAINTENANCE