Lincoln Electric IDEALARC SP-255 Service Manual page 74

F-21
ACTIVE SCR RECTIFIER ASSEMBLY TEST
TEST PROCEDURE
1. Disconnect main AC input power to
the machine.
2. Disconnect Molex Plugs J3 and J6
from the G2801 Control Board.
See Figure F.5.
J2
J7
J4
J5
J6
FIGURE F.5 - Control Board Molex
Plug Locations for G2801 PC Control
Board.
3. Test with an Analog Volt-Ohm meter
that capacitors have completely dis-
charged.
4. Disconnect leads X2 and X3 from the
negative capacitor bank using a 1/2"
open end wrench.
See Figure F. 6.
TROUBLESHOOTING & REPAIR
SP-255 CONTROL
G2801
J8
FIGURE F.6 - Location of Leads X2
and X3.
5. Separate leads X2 and X3 from the
J3
J9
NOTE: DO NOT DISASSEMBLE THE
SCR RECTIFIER HEAT SINK ASSEM-
BLY.
6. Construct the circuit shown in Figure
IDEALARC
LEADS
X2 AND X3
NEGATIVE
CAPACITOR
BANK
BUSS BAR
negative capacitor bank buss bar.
Be sure there is no electrical contact.
See Figure F6.
F.8. 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. Battery volt-
age should be 4.5 volts or
higher. If lower, replace the bat-
tery.
® SP-255
F-21