Three methods to determine the three pins of a triode
The first method: For a pointer meter with a jack for measuring the hFE of a triode, first measure the b pole, then insert the triode into the jack at will (of course the b pole can be inserted accurately), measure the hFE value, and then Turn the tube upside down and measure it again. If the hFE value is larger, the insertion position of each pin is correct.
The second method: For meters without hFE measurement jacks, or if the tube is too large to be inserted into the jack, you can use this method: For NPN tubes, first measure the b pole (whether the tube is NPN or PNP and its b pin) It’s easy to measure, right?), put the meter in the R C terminal, use your fingers to pinch the tip of the test lead and the pin at the same time, pick up the tube, lick the B terminal with the tip of your tongue, and see that the pointer on the meter head should deflect to a certain extent. If you connect the test leads correctly, the pointer deflection will be If it is larger, if it is not connected correctly, the pointer will deflect smaller, and the difference is obvious. From this, the c and e poles of the tube can be determined. For PNP tubes, connect the black test lead to the assumed e pole (do not touch the pen tip or pin with your hand), and connect the red test lead to the assumed c pole. At the same time, pinch the tip of the test lead and the pin with your fingers, and then lick b with the tip of your tongue. Extremely, if the test leads are connected correctly, the pointer on the meter head will deflect relatively large. Of course, the test leads need to be exchanged and measured twice during measurement, and the final judgment can be made only after comparing the readings. This method is suitable for triodes of all shapes and is convenient and practical. According to the deflection amplitude of the watch hand, 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 tube and its b pole, then put the meter in the R×10kΩ range. For NPN tubes, when the black test lead is connected to the e pole and the red test lead is connected to the c pole, the meter needle may have a certain Deflection, for PNP tubes, when the black test lead is connected to the c pole and the red test lead is connected to the e pole, the meter needle may deflect to a certain extent, but there will be no deflection in reverse. From this, the c and e poles of the triode can also be determined. However, for high pressure pipes, this method is not applicable.
For common imported models of high-power plastic-sealed tubes, the C pole is basically in the middle. Some b's of medium and small power tubes are most likely to be in the middle. For example, the b pole of the commonly used 9014 triode and its other series of triodes, 2SC1815, 2N5401, 2N5551 and other triodes are in the middle. Of course, they also have the c-pole in the middle. Therefore, when repairing and replacing transistors, especially these low-power transistors, do not just install them as they are, you must test them first.
