How do I test a transistor?
Hook the positive lead from the multimeter to the to the BASE (B) of the transistor. Hook the negative meter lead to the EMITTER (E) of the transistor. For an good NPN transistor, the meter should show a voltage drop between 0.45V and 0.9V. If you are testing PNP transistor, you should see “OL” (Over Limit).
How do you test a SMD transistor in a circuit?
Connect the base terminal of the transistor to the terminal marked positive (usually coloured red) on the multimeter. Connect the terminal marked negative or common (usually coloured black) to the collector and measure the resistance. It should read open circuit (there should be a deflection for a PNP transistor).
How can you tell if a transistor is bad?
A bad transistor can sometimes be detected by its partly burned or distorted appearance, but more often there is no visible indication. One approach to troubleshooting is to substitute a known good component, but that is a costly way to go.
How do you know if a transistor is defective?
Connect the positive probe of the DMM to the base or the “P” or the base of the above figure for the NPN type. Connect the negative probe to the “N” or the emitter. A good transistor will read a voltage around 0.7V. A bad transistor will read otherwise.
How do you tell if a transistor is shorted?
If the resistance is low in both directions, the transistor is shorted. Also, you can measure from the base to the collector in the same way. If the resistance is low in both directions, the transistor is shorted. Normally the base to emitter resistance will be high in one direction, low in the reverse direction.
How do I know if my varistor is bad?
Touch one meter probe to the free varistor lead and the other probe to the connected lead. Read the resistance on the meter. If it reads nearly infinite resistance, the varistor is still good. If it reads very low resistance, the varistor is blown.