Often, when a transistor fails, the entire device, of which it is included, becomes inoperative. To determine if the device has deteriorated, it must be checked. This will require simple equipment that is available to almost every home craftsman.
Necessary
- - soldering iron, neutral flux and solder;
- - tester or multimeter;
- - transistor tester.
Instructions
Step 1
De-energize the device containing the transistor. Solder it, remembering the pinout. Often, it is indicated directly on the board which electrode of the device is connected to where. If these data are not available, find them in a reference book or on the Internet.
Step 2
The simplest way to test a transistor is to connect it to a special connector on a multimeter. It indicates to which sockets to connect which electrodes of the device, depending on its structure. The limit switch in this case must be in the position marked as "hFe". If the indicator shows the current transfer coefficient close to the nominal for this type of transistor, it means that it is working properly.
Step 3
A more complex check is performed with a tester or multimeter in ohmmeter mode. For a device with an n-p-n structure, both junctions (collector and emitter) must open with a positive voltage at the base, and for a p-n-p structure transistor, with a negative one. In reverse polarity, the transitions should close. For a digital multimeter in ohmmeter mode, the minus is usually on the black probe, for a pointer tester, vice versa. Be sure to find out in the instructions from the measuring device the short-circuit current in ohmmeter mode. It should not exceed the maximum allowable for the transitions of the transistor.
Step 4
Connect the collector of the n-p-n transistor to the positive of the power supply with a voltage of 3 - 4 volts through the circuit of the 1 kilo-ohm resistor and the LED (anode to positive). Connect the emitter directly to the minus of the same source. The LED should be off. Now connect the plus of the power supply through another 1K ohm resistor to the base of the transistor. The LED should light up. If you are testing a p-n-p transistor, reverse the polarity of the power supply and the LED.
Step 5
High voltage transistors can work fine when tested with low voltage, but break through in operation. Such a device will have to be changed in any case.
Step 6
If you need to check transistors often, assemble a special tester for this, for example, according to the following scheme:
Step 7
Based on the test results, decide whether to replace the transistor or install it back into the circuit.
