Lincoln Electric WIRE-MATIC 255 SVM 119-A Service Manual page 68

F-17
ACTIVE SCR RECTIFIER ASSEMBLY TEST (CONTINUED)
TEST PROCEDURE
1. Disconnect main AC input power to
the machine.
2. Disconnect Molex Plugs J3 and J6
from the G2803 Control Board.
See Figure F.5.
J10
J1
J7
J2
FIGURE F.5 - Control Board Molex
Plug Locations for G2803 PC Control
Board.
3. Verify that the capacitors have com-
pletely discharged with an Analog
Volt-Ohm meter.
4. Disconnect leads X2 and X3 from
the negative capacitor bank using a
1/2" open end wrench.
See Figure F. 6.
TROUBLESHOOTING & REPAIR
J3
J9
J6
J4
FIGURE F.6 - Location of Leads X2
and X3.
J5
5. Separate leads X2 and X3 from the
NOTE: DO NOT DISASSEMBLE THE
SCR RECTIFIER HEAT SINK ASSEM-
BLY.
6. Construct the circuit shown in Figure
WIRE-MATIC 255
LEADS
X2 AND X3
NEGATIVE
CAPACITOR
BANK
BUSS BAR
negative capacitor bank buss bar.
Be sure there is no electrical con-
tact. See Figure F.6.
F.7. One 6-volt lantern battery can
be used. R1 and R2 resistor values
are ±10%. 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 (C).
Close switch SW-1.
voltage should be 4.5 volts or
higher. If lower, replace the bat-
tery.
F-17
Battery