Maintenance - ESAB Heliarc 250 Instruction Manual

SECTION 4

4.1 Maintenance

If this Equipment does not operate properly, stop work
immediately and investigate the cause of the malfunction.
Maintenance work must be performed by an experienced
person, and electrical work by a trained electrician. Do
not permit untrained persons to inspect, clean, or repair
this Equipment. Use only recommended replacement
parts.
Be sure that the wall disconnect switch or circuit
breaker is open before attempting any inspection or
work inside of the power source. Always wear safety
goggles with side shields when blowing out the unit
with low pressure air.
A. CLEANING
Since there are no moving parts (other than the fan) in the
power source, maintenance consists mainly of keeping
the interior of the cabinet clean. Periodically, remove the
cover from the cabinet and blow accumulated dust and
dirt from the air passages and the interior components,
using clean low pressure air. It is imperative that the air
passages, to the interior of the unit, be kept free of dirt
accumulation to ensure adequate circulation of cooling
air, especially over the rectifier bridge plates and PC
boards. The length of time between cleaning will depend
on the location of the unit and the amount of dust in the
atmosphere.
B. LUBRICATION
Fan motors with old tubes require lubrication after 1 year
of service. Motors without oil tubes are permanently
lubricated and do not require any attention.
C. SPARK GAP SERVICING
This component is part of the high frequency assembly.
It will probably be necessary to readjust these gaps after
extended operation, or if erratic high frequency operation
is noted. It is important that the gaps be adjusted with a
feeler gauge rather than by eye. Cleaning and dressing of
spark gap points is not recommended since the points are
tungsten and difficult to file. Points (P/N 673578) should
be replaced as a set.
14
D. 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 .025 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
E. TESTING AND REPLACING BRIDGE ASSY. COM-
PONENTS
SCRs and silicon diodes are devices which allow current
to flow in only one direction and block current in the other
direction. The SCRs and silicon diodes used in this power
source are designed to provide long trouble-free opera-
tion; however, should a failure occur, they may require
replacement. The testing procedures to determine defec-
tive components are as follows:
1. Silicon Diode Rectifier, D1-D2.
Disconnect the power lead to the diode in order to
provide an open-circuit across the component to be
tested. Using an ohmmeter set to the R x 1 scale,
check the resistance in the forward and reverse
direction. A good diode will read high in reverse
direction and low in the forward direction.
4-1
MAINTENANCE