Lincoln Electric IDEALARC DC-1000 Service Manual page 74

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FIGURE F.17 – SILICON CONTROLLED RECTIFIER (SCR) TEST SETUP
5. To test SCRs, construct the circuit outlined in
Figure F.17. Use one 6V lantern battery.
Resistor values are in ohms ±10%. The volt-
meter scale should be low, approximately 0-5 or
0-10 volts.
BATTERY TEST
Check the battery by shorting leads (A) and (C)
and then close switch SW1. Replace battery if volt-
age is less than 4.5 volts.
A. Connect SCR into the test circuit as shown (A)
lead to anode (C) lead to cathode and (G) lead
to the gate.
B. Close switch SW1 (switch SW2 should open),
voltmeter should read zero. If the voltmeter
reads higher than zero the SCR is shorted.
NOTE: Do not disassemble the heat sinks.
TROUBLESHOOTING AND REPAIR
ACTIVE SCR TEST (continued)
IDEALARC
6. With switch SW1 closed, close switch SW2 for
two seconds and release. The voltmeter should
read 3 to 6 volts before and after switch SW2 is
released. If the voltmeter does not read, or
reads only while SW2 is depressed, the SCR or
battery is defective (repeat Battery Test
Procedure).
7. Open switch SW1, disconnect the gate lead (G)
and reverse the (A) and (C) leads on the SCR.
Close switch SW2. The voltmeter should read
zero. If the voltage is higher than zero, the SCR
is shorted.
8. Replace any SCR assembly that does not pass
test in Step 4.
® DC-1000
F-40