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TROUBLESHOOTING & REPAIR | ||
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ACTIVE SCR TEST
FIGURE F.17- Silicon Controlled Rectifier (SCR) Test Setup
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5.To test SCRs, construct the circuit outlined in Figure F.17. Use one 6V lantern battery. Resistor values are in ohms ±10%. The voltmeter scale should be low, approximately
BATTERY TEST
Check the battery by shorting leads (A) and (C) and then close switch SW1. Replace battery if voltage 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.
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 bat- tery 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.