E-9
TROUBLESHOOTING
E-9
(high resistance value). This indicates that the
capacitor in the snubber circuit is taking a
charge.
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 on the terminal strip
(codes below 9500) or Amphenol (codes above
9500), 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
For codes above 9500, the remote control
Amphenol 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 resis-
tance 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 partially shorted rheostat. A
very high reading will indicate an open rheostat. In
either of the last two cases, replace rheostat. Check
cable for any physical 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 SCR’s 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 375-I, 500-I AND 600-I
CAUTION
