Lincoln Electric IM10111 IDEALARC R3R-500-I - Manual (Page 21)

E-9 TROUBLESHOOTING E-9
3. If the needle stays to the right, the capacitor is
shorted and the assembly is defective.
4. If the needle does not move, the capacitor is
open and the assembly is defective.
G.CHECKING CURRENT CONTROL
RHEOSTAT ON MACHINE
1. Turn machine off.
2. Remove the control panel screws and open the
front cover.
3. Turn the current control switch to remote.
4. Disconnect the harness plug from the control
board.
5. Put current range switch to B range.
6. With an ohmmeter on X1K, connect it to lead
210 and 211 on SW #2. Rotate the current con-
trol rheostat. The resistance reading should be
from around zero to 10K ohms. Check the resis-
tance reading between 75 in the Remote Control
Receptacle and 211 on SW #2. The reading
must be 10K ohms. No reading will indicate an
open rheostat and low reading will indicate a
shorted or partially shorted rheostat; in either
case, replace.
H. TOGGLE SWITCH CHECK
1. Turn off the machine power input. SW-1 has 110
volts across it when the input power is connect-
ed.
2. Isolate the switch to be tested by removing all
connecting leads.
3. Check to make sure the switch is making con-
nections with a VOM meter. The meter should
read zero resistance.
4. Put the ohmmeter on X1K scale and measure
the resistance between the terminal and the
case of the machine (touch a self-tapping
screw). Reading should be infinite.
5. If either step (3) or step (4) fails, replace the
switch.
I. REMOTE CONTROL CHECK
The Remote Control Receptacle pin assignments
are: pin C-75, pin B-76, and pin A-77. Disconnect
the remote field control and connect an ohmmeter
across 75 and 76 and rotate the rheostat in the
remote control. The resistance reading should go
from zero to 10K ohms. Repeat with triplet across
77 and 76 with same results. Connect ohmmeter
across 75 and 77. The reading should be 10K
ohms. A lower reading will indicate a shorted or par-
tially shorted rheostat. A very high reading will indi-
cate an open rheostat. In either of the last two
cases, replace rheostat. Check cable for any phys-
ical damage.
J. POWER RECTIFIER BRIDGE ASSEM-
BLY CHECKING PROCEDURE
The rectifier bridge tests outlined below will iden-
tify the most common effects found in power
diodes or power silicon controlled rectifiers. If a
bridge problem still exists after test, please call a
Lincoln Field Service Shop. Further evaluation of
diodes or silicon controlled rectifiers may require
laboratory equipment.
1. DEVICE ISOLATION (see the instruction manu-
al Parts List for the exact location)
Disconnect the following leads from the bridge,
shown in Diagram 1:
a. Wiring harness gate leads (G1, G2, G3) from
the gate lead terminals (1) on the Control PC
board.
b. AC leads X1, X2 and X3 from the anodes of
the SCRʼs and cathodes of the diodes.
c. The 220, 221 and 223 leads from the
Snubber PC board.
d. Lead 220 that connects to the latching resis-
tor (R3).
e. The cathode of each diode (4 total).
(1) Connector J4 on latest control board.
IDEALARC ® R3R-500-I
CAUTION