There are two ways to judge whether a transistor is good or bad:
Transistor, whose full name is semiconductor triode, is also called bipolar transistor and transistor. It is a semiconductor device that controls current. Its function is to amplify weak signals into larger amplitude electrical signals. It is also used as a contactless switch. The transistor is one of the basic components of semiconductors. It has the function of current amplification and is the core component of electronic circuits. The transistor is made of two PN junctions that are very close to each other on a semiconductor substrate. The two PN junctions divide the entire semiconductor into three parts. The middle part is the base area, and the two sides are the emitter area and the collector area. The arrangement is PNP and NPN.
1. How to identify base and tube types:
Use R×100 gear for measuring germanium tubes and R×1K gear for silicon tubes. First, fix the red test lead in contact with any one of the legs, and measure the remaining two legs with the black test lead. See if you can measure the two smaller resistance values. If you can't move the red test lead to the other pins, continue to measure until two small resistances are reached. If you can't find two small resistors by fixing the red test lead, you can fix the black test lead and continue searching. . After finding two small resistors, the pin used by a fixed test lead is the base.
If the fixed test lead is a black test lead, the transistor is NPN type; if the fixed test lead is a red test lead, the transistor is PNP.
2. Distinguish collector:
Because the β is large when the emitter and collector of the transistor are correctly connected (the hands of the watch swing greatly), and the β is much smaller when the transistor emitter and collector are connected in reverse. Therefore, first assume that there is a collector connected with an ohmic gear (for a PNP tube, the emitter is connected to the black test lead and the collector is connected to the red test lead). When measuring, pinch the base and the assumed collector with your hands (or connect it with a 100KΩ resistor). The two poles should not be in contact. If the pointer swings greatly, but the pointer swings small after the two poles are reversed, it means that the assumed collector is correct. , thereby determining the collector and emitter.
If the transistor has the resistance value you mentioned above, either the multimeter is faulty or the transistor is bad. It is better to first find a good triode and measure it according to the above method and then compare it, so that you can judge whether it is good or bad and sum up experience.
