| Electronics > Beginners |
| Controversy on Transistor Testing: Can't be both! |
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| Benta:
--- Quote from: billbyrd1945 on November 26, 2018, 02:32:54 pm ---I had looked at every 13005 datasheet I could find, but didn't understand the circuitry. So I resorted to YouTube. Here's an image of the circuitry on one datasheet. I've added red to what I suspect you're saying explains why E will flow to C, but not vice-versa. --- End quote --- Whoever made that schematic must have been on prohibited substances. The (MJE)13005 is a completely normal high voltage NPN transistor (400 V). The 13005D is the same, with the addition of a diode from emitter to collector. This is often seen in switching transistors. Ignore the derogatory comments, this is the "Beginners" section. |
| billbyrd1945:
Thank you for your kindness sir. |
| nsrmagazin:
If you are working on circuits without knowing the basics you risk hurting yourself. The very least you can burn your circuit. Its better to start with the principles that you don't know, instead of just getting a ready answer. EDIT: and I did not say you are stupid! What I meant is you should start with the beginning! |
| billbyrd1945:
Finally found two things that I could actually measure, an opamp and what I think is a transformer. I replaced the opamp and all the caps. I have 110vac going to the transformer and about 1 volt coming out. Out of circuit, the primary and secondary (if that's what they are) test open. The number on the transformer is UM-007/UF 16-45 and seems to exist no where except on my boards. So I don't have any way of knowing what to order. The boards ultimately produce 12vdc. But I don't know if that means the transformer in question should be replaced with 110vac/12vdc or something else. Any help with be appreciated. |
| rhb:
The forward voltage drop across the base emitter junction is higher than the drop across the base-collector junction. With older meters you can use the resistance range. The lower resistance is the base collector junction because it has larger area. Newer meters you'll need to use the diode test function to get enough voltage to get the junction to conduct. If it's not just a transistor I can't say what to expect.The BSIDE ESR02 Pro is $20, has a nice case and seems to do a good job. But I used the method in the first paragraph for 40 years. I learned it from a semiconductor physicist who was teaching an intro electronics class in the building next to where I was looking at rocks through a microscope all day. I didn't take the course, I just went to the lectures for a break. In the 40 ears since, I have encountered two people who knew how to do this. Everyone knows how to find the base, but knowing how to identify the collector and emitter is is uncommon in my experience. I find that sad as it is so simple and logical. |
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