E-8
TROUBLESHOOTING
E-8
TROUBLESHOOTING
PROCEDURES
A. PROCEDURE FOR REPLACING PC
BOARDS
When a PC board is to be replaced, the following
procedure must be followed:
1. Visually inspect PC board in question. Are any of
the components damaged? Is a conductor on
the back side of the board damaged?
a. If there is no damage to the PC board, insert
a new one and see if this remedies the prob-
lem. If the problem is remedied replace the
old PC board and see if the problem still
exists with the old PC board.
1. If the problem does not exist with the old
board, check the PC board harness plug
and PC board plug for corrosion, contam-
ination, or oversize.
2. Check leads in the harness for loose con-
nections.
b. If there is damage to the PC board, refer to
the Troubleshooting Guide.
B. PROCEDURE FOR CHECKING DIODES
1. Isolate the diode
in
question.
(Electrically dis-
connect
from
other circuits.)
2. Use an ohmme-
ter X10 scale.
Connect
the
meter across the
diode and note
the
resistance
value. Reverse the ohm-meter leads and note
the resistance value.
Shorted diode – Low resistance readings in both
directions.
Open diode – High or infinite resistance in both
directions.
Good diode – One reading will be high or infinite
and the other reading will be low.
C. CONNECTING THE REMOTE CONTROL
TO THE MACHINE
Extreme caution must be observed when installing
or extending the wiring of a remote control.
Improper connection of this unit can Lead to failure
of the current control rheostat or the control circuit.
Only the green lead can and should be grounded to
the machine case. When extending the standard
remote control make sure the leads are the same
and the splice is waterproof. Be very careful not to
ground the cable when in use and do not let these
connections touch against the case.
D. OUTPUT VOLTAGE
The open circuit voltage of the machine should be
66 to 71 volts and should not vary when the rheo-
stat is varied unless the machine is welding. If any
other condition exists, refer to the Troubleshooting
Guide.
E. FAULT PROTECTION OPERATION
The overload protection circuit, in the control board,
will reduce the welding current (heat) to some safe
value if the machine is overloaded for 2 to 3 sec-
onds. The overload values are as appears in the fol-
lowing table.
F. CHECKING SNUBBER CIRCUIT
In case of an SCR malfunction or failure, the snub-
ber assembly should be checked. Turn the machine
off and disconnect one lead of the snubber assem-
bly. (Either 221, 222 or 223 depending on the SCR
in question. See wiring diagram.) The sides of the
machine have to be removed to do this. (See the
instruction manual parts list for the exact location.)
1. Visually inspect the snubber assembly for over-
heated components.
2. Using a VOM meter on the X10 scale, connect
the positive lead to the lead removed. Touch the
negative lead to the other lead still connected to
the SCR bridge. The indicating needle on the
meter will move quickly to the right (low resis-
tance value) and then slowly return to the left
IDEALARC® R3R 375-I, 500-I AND 600-I
Machine Name
f
Load Current ±5%
R3R 375-I
R3R 500-I
50 Hz
100 A
R3R 600-I
