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TROUBLESHOOTING GUIDE
Trouble
Cause
What To Do
Input contactor (CR1 chatters).
Machine input contactor does not
operate.
Machine input contactor operates,
but no output when trying to weld.
Machine has minimum output and
no control.
Machine has high output and no
control.
1. Faulty input contactor (CR1).
2. Low line voltage.
1. Supply line fuse blown.
2. Contactor power circuit dead.
3. Broken power lead.
4. Wrong input voltage.
5. Open input contactor coil.
6. POWER “
I/O
” switch (S1) not
closing.
1. Circuit between #2 (C ) and #4
(D) is not being closed.
2. Electrode or work lead loose or
broken.
3. Open main transformer (T1) pri-
mary or secondary circuit.
4. Defective Control PC Board.
5. Primary or secondary ther-
mostats open.
1. Terminals 75, 76, or 77 grounded
to positive output.
1. Terminals 75, 76, or 77 grounded
to negative output.
1. Repair or replace.
2. Check input power.
1. Replace if blown - look for reason
first.
2. Check control transformer T2
and associated leads.
3. Check input voltage at contactor.
4. Check voltage against instruc-
tions.
5. Replace coil.
6. Replace switch.
1. Make sure trigger circuit is being
closed.
2. Repair connection.
3. Repair
4. Replace. See Procedure for
Replacing PC Boards.
5. Amber thermal protection light is
on: Check for overheating; make
sure fan is operating and there is
no obstruction to free air flow.
1. Check 75, 76, or 77 for ground to
positive output circuit. Nearly
zero ohms to ground indicates a
grounded circuit. A value greater
than a few thousand ohms is nor-
mal. Self-restoring fuses on PC
Board automatically reset within
a few seconds after ground is
cleared.
1. Check 75, 76, or 77 for ground to
negative output circuit. Nearly
zero ohms to ground indicates a
grounded circuit. A value greater
than a few thousand ohms is nor-
mal. Self-restoring fuses on PC
Board automatically reset within
a few seconds after ground is
cleared.
Summary of Contents for CV 500-I
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