Lincoln Electric IDEALARC CV-300 Service Manual page 59

F-20
ACTIVE SCR RECTIFIER ASSEMBLY TEST (CONTINUED)
6. Disconnect the D4 diode pigtail from
the positive strap. See Figure F.14.
FIGURE F.14 - Procedure to discon-
nect the D4 diode pigtail from the
positive strap.
7. Remove the red insulating paint
from the heat sink test points. See
Figure F.15.
FIGURE F.15 - Heat sink test points.
TROUBLESHOOTING & REPAIR
IDEALARC CV-300
NOTE: DO NOT DISASSEMBLE THE
SCR RECTIFIER HEAT SINK ASSEM-
BLY.
8. Construct the circuit shown in Figure
F.16. One 6-volt lantern battery can
be used. R1 and R2 resistor values
are 010%. Set voltmeter scale low,
at approximately 0-5 volts or 5-10
volts.
a. Test the voltage level of the bat-
tery. Short leads (A) and (B).
Close switch SW-1.
voltage should be 4.5 volts or
higher. If lower, replace the bat-
tery.
9. Connect the Tester to the SCR 1 as
shown in Figure F.16.
a. Connect Tester lead (A) to the
anode.
b. Connect Tester lead (C) to the
cathode.
c. Connect Tester lead (G) to the
gate.
ANODE
CATHODE
FIGURE F.16 - SCR Tester Circuit and
SCR connections.
F-20
Battery