How to use a multimeter to determine the good and bad transistor
Using the one-way conductivity of the PN junction within the transistor, check the positive and negative resistance of the PN junction between the poles, if the difference is large that the tube is good, if the positive and negative resistance are large, indicating that there is a break in the internal tube or the PN junction performance is not good. If the positive and negative resistance are small, indicating that the tube is shorted between the poles or breakdown.
Using digital and pointer table to identify the NPN transistor good or bad
A digital multimeter placed in the pn junction block
Red pen to B, black pen to E, if the highest bit still shows 1, it means that the emission junction does not work, judge bad;
Red pen to B, black pen to C, if the highest bit still shows 1, then the collector junction does not work, judge bad.
Red pen to C, black pen to E, if the display becomes a limited number or even drip ringing, it shows that the C-E breakdown, judgement bad.
Second, the pointer multimeter placed in the X1k resistance block
Black pen to B, red pen to E, if the needle does not move, then the launch junction does not work, judge bad;
Black pen to B, red pen to C, if the needle does not move, then the collector junction does not work, judge bad.
Black pen to C, red pen to E, if the needle is swinging, then the C-E breakdown, judge bad.
Triode judgement of good and bad, can be carried out in accordance with the following methods:
1. The method of judging the base pole and tube type:
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 values, 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 sum up the experience.
