Troubleshooting & repair, Static scr/diode rectifier bridge test (continued) – Lincoln Electric IDEALARC R3R-500 User Manual
Page 61
TROUBLESHOOTING & REPAIR
F-27
F-27
IDEALARC R3R
STATIC SCR/DIODE RECTIFIER BRIDGE TEST (continued)
7. Remove the red insulating paint from the
heat sink test points. See Figure F.15.
NOTE: Do not disassemble the heat sink.
8. Measure the resistance from the anode to
the cathode of SCR 1 using an analog
volt/ohmmeter (multimeter) set at R x 1000
scale. See Figure F.15.
a.
Reverse the meter leads and measure
the resistance from the cathode to the
anode of SCR 1. See Figure F.15.
b.
If a low resistance is measured in
either meter polarity, SCR1 is faulty.
Replace SCR 1.
9. Test the resistance of SCR 2 and SCR 3
using the same procedure described in
Step 8.
10. Measure the resistance of diode D1 from
anode (+probe) to cathode (-probe) using
an analog ohmmeter set at R x 1000 scale.
The resistance should be low. See Figure
F.15.
a.
Reverse the meter leads and measure
the resistance from cathode (+probe)
to anode (-probe) of diode D1. The
resistance should be high. See Figure
F.15.
b.
If a low resistance is measured in both
meter polarities, diode D1 is shorted.
Replace diode D1.
c.
If a high resistance is measured in both
meter polarities, diode D1 is open.
Replace diode D1.
11. Test diodes D2, D3 and D4 for proper oper-
ation using the same procedure described
in Step 10.
12. Reconnect all leads and molex plugs.
Resolder lead #204 at resistor R3.
13. If this test did not identify the problem or to
further test the SCRs, go to the Active
SCR Test.
FIGURE F.15 – HEAT SINK AND SCR TEST POINTS
REMOVE
INSULATING
PAINT
CATHODE
ANODE