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D-4
TROUBLESHOOTING
D-4
Observe all Safety Guidelines detailed througout this manual
If for any reason you do not understand the test procedures or are unable to perform the tests/repairs safely, contact your Local
Authorized Field Service Facility for technical troubleshooting assistance before you proceed.
CAUTION
FUNCTION PROBLEMS
PROBLEMS
(SYMPTOMS)
POSSIBLE CAUSE
RECOMMENDED
COURSE OF ACTION
E. Machine does not have
maximum output (67 to 71 volts).
F. Machine comes on but soon trips
off while under load and High
Temperature Warning Light
glows. (Choke or Secondary
thermostat tripped)
G.Machine comes on but reduces
to low output under load and
remains there until the load is
broken and arc re-started. See
Fault Protection Operation
Section.
1. Input fuse blown. Machine is
single phased.
2. One phase of main transformer
windings open.
3. Defective power bridge.
1. Improper ventilation.
2. Loaded beyond rating.
3. Fan inoperative.
4. Shorted diode or SCR in power
rectifier bridge.
5. Defective thermal fan thermostat
1. Excessive load causing the over-
load protection on control board
to operate.
2. Machine output shorted causing
overload protection on control
board to operate.
3. Control circuit defective.
1. Replace fuse or repair input line.
Check reason for fault.
2. Repair.
3. Check bridge. See
Troubleshooting Procedures –
Checking Snubber Circuit and
Power Rectifier Bridge Assembly.
1. Make sure all case openings are
free for proper circulation of air.
2. Operate at rated current and
duty cycle.
3. Check leads, choke and sec-
ondary thermostat and motor
bearings. Fan can be tested on
115 volt line. Check thermal fan
thermostat.
4. Refer to Power Hybrid Bridge
Checking Procedure. See
Troubleshooting Procedures –
Checking Snubber Circuit and
Power Rectifier Bridge Assembly.
5. Replace
1. Reduce load.
2. Turn machine off and remove
short.
3. Replace per PC board replace-
ment. See Troubleshooting
Procedures – Replacing PC
Boards.
E500