The triode can be judged good or bad in the following way:
1. Base and tube type discrimination method:
Measured germanium tube with R × 100 file, silicon tube with R × 1K file, first fixed red pen and any one foot contact, black pen were measured on the remaining two feet. See if you can measure to two smaller resistance value, if not then move the red pen to the other foot to continue to measure the two small resistors, if the fixed red pen can not find two small resistors, you can fix the black pen to continue to find. When you find two small resistors, a fixed pen used for the base of the foot.
If the fixed pen for the black pen, the transistor for the NPN type, if the fixed for the red pen, the tube is PNP.
2. Identify the collector:
Because the transistor emitter and collector correctly connected β is large (the needle swing is large), reverse connection β is much smaller. Therefore, the first assumption of a collector, with ohm gear connection, (for PNP-type tube, the emitter connected to the black pen, collector connected to the red pen). Measurement, hand pinch (or connect with a 100KΩ resistor) the base and the assumed collector, the two poles can not be contacted, if the pointer swing is large, while the two poles are adjusted to the pointer after the pointer swing is small, it means that the assumption is the correct collector, so as to determine the collector and the emitter.
According to the resistance value of the triode you described above is either the multimeter is faulty, or the triode is bad. Or first find a good triode according to the above method of measurement and then compare, you can determine the good and bad as well as lessons learned.
Triode pin must be correctly identified, otherwise, access to the circuit not only can not work properly, but also may burn the transistor. If you know the type of transistor and its electrode, you can judge the good and bad transistors by the pointer multimeter as follows.
① Measure NPN transistor: set the ohmmeter at R × 100 or R × lk, connect the black pen to the base, connect the red pen to the remaining two poles successively, if the two measured resistance values are small, and then connect the red pen to the base, connect the black pen to the remaining two poles successively, if the two measured resistance values are very large, then it means that the transistor is good.
② Measure PNP transistor: the multimeter ohmmeter set R × 100 or R × lk at the red pen connected to the base, the black pen has been connected to the remaining two poles, if the two measured resistance values are small, and then connect the black pen to the base, the red pen has been connected to the remaining two poles, if the two measured resistance values are very large, then the transistor is good.
When the marking on the transistor is not clear, you can use a multimeter to determine the initial good or bad transistor and type (NPN type or PNP type), and identify the e, b, c three electrodes. Test methods are as follows
① Pointer multimeter to determine the base b and the type of transistor: the multimeter ohm block set R × 100 or R × lk at the first assumption of a transistor pole base, and the black pen connected to the assumption of the base, the red pen has been connected to the remaining two poles, if the two measured resistance values are very small (or about a few hundred ohms to a few thousand ohms), the assumption of the base is correct, and the measured transistor NPN type tube; the same, the same, the measured transistor NPN type tube. If the resistance values are very large (about several thousand ohms to several thousand ohms), then the assumed base is correct and the triode under test is a PNP-type tube. If the two measured resistance value is a large and small, then the original assumption of the base is wrong, then you must re-assume that the other electrode for the base, and then repeat the above test.
② judge the collector c and emitter e: still pointer multimeter ohm block set R × 100 or R × 1k at the NPN tube, for example, the black pen connected to the assumption of the collector c, the red pen connected to the assumption of the emitter e, and hand pinch the b and c poles ( can not make direct contact with the b, c ), through the human body, quite b, C, between the access to the bias resistor, read out the head of the resistance, and then two pens reversed and retested. Then reverse the two pens and retest. If the first measured resistance is smaller than the second, that the original hypothesis is valid, because c, e asked the resistance value is small that the current through the multimeter is large, the bias is normal. Now the pointer multimeter have to measure the triode amplification (Hfe) interface. You can estimate the amplification of the triode.
