Some models of testers are equipped with built-in meters for the gain of low-power transistors. If you do not have such a device, then the health of the transistors can be checked with a conventional tester in ohmmeter mode, or using a digital tester in diode test mode.
Instructions
Step 1
To test bipolar transistors, connect one probe of the multimeter to the base of the transistor, bring the second probe alternately to the emitter and collector, then change the probes and repeat the same steps. Please note that inside the electrodes of many digital or powerful transistors there can be protective diodes between the collector and the emitter and built-in resistors between the base and the emitter or in the base circuit, if you do not know this, then by mistake you may consider this element as faulty.
Step 2
When checking field-effect transistors, keep in mind the fact that they come in a wide variety of types. For example, the check of transistors having a gate based on a pn-junction blocking layer is carried out as follows. Take a conventional dial-up ohmmeter or digital (the second is more convenient).
Step 3
Measure the resistance between drain and source, it should be small and approximately equal in both directions. Now measure the forward and reverse resistance of the junction, for this, connect the probes to the gate and drain (or source). If the transistor is good, the resistance will be different in both directions.
Step 4
When you check the resistance between the drain and the source, remove the charge from the gate, for this, close it with the source for a couple of seconds, if this is not done, you will get a non-repeating result. Most low power field effect transistors are extremely static sensitive. Therefore, before you take the transistor in your hands, make sure that there are no charges left on your body. To get rid of them, touch any grounded device with your hand (a heating battery will do). Powerful field-effect transistors are most often equipped with static protection, but even despite this, protection when working with them will also not damage.
