Connect the marked terminal as positive, first to the collector and measure the resistance. Then take it to the transmitter. In both cases, the counter must deviate (indicate open circuit for a PNP transistor). Subsequently, the negative or common counter must be connected to the collector and the positive counter at the transmitter.
Transistor test: Remove the transistor from the circuit for accurate test results.
Step 1: (based on the emitter)
Connect the positive conductor from the multimeter to the BASE (B) of the transistor. Connect the negative cable to the EMITTER (E) of the transistor. For a good NPN transistor, the meter should display a voltage drop between 0.45 V and 0.9 V. If you are testing a PNP transistor, you should see “OL” (Over Limit).
Step 2: (Collector base)
Keep the affective cable on BASE (B) and place the negative cable on the COLLECTOR (C).
For a good NPN transistor, the meter should display a voltage drop between 0.45 V and 0.9 V. If you are testing a PNP transistor, you should see “OL” (Over Limit).
Step 3: (Base Transmitter)
Connect the positive cable from the multimeter to the transistor ether (E). Connect the negative cable to the transistor BASE (B) connector.
For a good NPN transistor, you should see “OL” (Over Limit). If you test the PNP transistor, the meter should exhibit a voltage drop of 0.45 V to 0.9 V.
Step 4: (Basic Collector)
Attach the positive cable from the multimeter to the transducer COLOR (C). Connect the negative cable to the transistor BASE (B) connector.
For a good NPN transistor, you should see “OL” (Over Limit). If you test the PNP transistor, the meter should exhibit a voltage drop of 0.45 V to 0.9 V.
Step 5: (Collector for emitter)
Connect the meter cable to the COLLECTOR (C) and the negative counter leads to the transmitter (E). – A good NPN or PNP transistor will read the “OL” / upper limit of the instrument. Change the conductors (positive to the transmitter and negative to the collector) – Again, a good NPN or PNP transistor should read “OL”.
If your bipolar transistor measures against these steps, consider it negative.
You can also use the voltage drop to determine which emitter drives a non-marking transistor because the base-emitter junction generally has a slightly lower voltage drop than the base collector junction.
Note: this test only checks if the transistor is short-circuited or open, does not guarantee that the transistor operates in the projected parameters. It should only be used to help you decide whether you need to replace or switch to the next component. This test only works on bipolar transistors: you must use a different method to test the FETs.
