How to Accurately Identify Three Pins of a Transistor with a Multimeter
The b-pole of a transistor is easy to measure, but how can we determine which one is c and which one is e? Here are three recommended methods: the first method: for a pointer meter with a tested transistor hFE socket, first measure the b-pole, then insert the transistor into the socket at will (of course, the b-pole can be inserted accurately), measure the hFE value, and then invert the transistor to measure again. The larger hFE value is measured once, and the correct position of each pin is inserted. The second method: For meters without hFE measuring sockets or for tubes that are too large to be inserted into sockets, this method can be used: for NPN tubes, first measure the b-pole (whether the tube is NPN or PNP and its b-pin are easy to measure, right? )Place the watch in the R × 1k Ω range, connect the red probe to the assumed e pole (be careful not to touch the tip or pin of the red probe with your hand), and connect the black probe to the assumed c pole. At the same time, pinch the tip and pin of the watch with your fingers, pick up the tube, and use your tongue to lick the b pole. Check that the pointer on the watch head should have a certain deviation. If you connect the probes correctly, the deviation of the pointer will be larger. If you connect them incorrectly, the deviation of the pointer will be smaller. The difference is very obvious. From this, the c and e values of the pipe can be determined
Extreme. For PNP tubes, connect the black probe to the assumed e pole (do not touch the pen tip or pin), and the red probe to the assumed c pole. At the same time, pinch the pen tip and pin with your fingers, and then lick the b pole with your tongue. If each probe is connected correctly, the pointer of the meter head will deflect significantly. Of course, when measuring, the probes need to be exchanged twice to compare the readings before making a final decision. This method is applicable to all shapes of transistors and is convenient and practical. Based on the deflection amplitude of the pointer, the amplification ability of the tube can also be estimated, of course, this is based on experience. The third method: First, determine the NPN or PNP type of the transistor and its b-pole, then place the meter in the R × 10k Ω range. For NPN transistors, when the black probe is connected to the e-pole and the red probe is connected to the c-pole, there may be a certain deviation in the needle. For PNP transistors, when the black probe is connected to the c-pole and the red probe is connected to the e-pole, there may be a certain deviation in the needle, and vice versa, there will be no deviation. This can also determine the c and e poles of the transistor. However, for high-pressure pipes, this method is not applicable.
For common imported high-power plastic sealed tubes, the C-pole is mostly in the middle (I haven't seen one with B in the middle yet). Some small and medium power transistors may have b in the middle. For example, the commonly used 9014 transistor and other models of transistors in the series, as well as 2SC1815, 2N5401, 2N5551 and other transistors, have their b-pole in the middle. Of course, they also have a C-pole in the middle. So when repairing or replacing transistors, especially these low-power transistors, they should not be installed directly as they are. They must be tested first.
