| Electronics > Projects, Designs, and Technical Stuff |
| I have a short ( i think) and don't know where to start |
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| Hextejas:
Progress ! The V-, left and right show -13V ! Hmmm, can I check the MUR860 while still in the circuit ? I checked the resistance of a new one before soldering and it showed a resistance of 0. The leg with the new diodes and that yields -13v, the 4 diodes all read 0 resistance. The other leg, all the diodes show some resistance. I think that I will replace all 4 of them. |
| sokoloff:
Your circuit has two logical "halves". (If you wanted to, you would) Connect the 9VAC wall wart across either U1 and U2 or U3 and U4. However, given that you have a DC bench power supply with current limiting, just use that to find the short. It's not quite as useful for troubleshooting the bridge rectifier, but your problem is not in the AC rectification part of the circuit. (I asked if you had a wall wart because I bet many more people can put their hands on that than on a bench power supply. You have the bench supply. That's way more effective in short-finding.) |
| Hextejas:
I think its fixed. I hooked up the full mains voltage and no smoke or fire. Success as the output voltages read correctly. Sheesh, what a hassle but finally solved and thanks to all the excellent help here. Thank you again. I hope that all my projects will go smoother. :popcorn: |
| sokoloff:
What did the problem end up being? :-// |
| nick_d:
To check the diodes use the diode setting on the meter. Ohms is meaningless for diodes, since current increases super-linearly with voltage, not linearly. The diode setting puts a specified current through the diode and tells you the voltage. In forward orientation it should show about 0.6V, larger for beefy power diodes (up to about 1V) or LEDs (up to about 3V). In reverse orientation it should show infinite. You should be able to do this test with them soldered into the board and no supply or load connected. If result is correct then it is a pretty good indication of diode health (though not absolutely definitive). Likely your previous issue was with damaged but not visually obviously damaged diodes. cheers, Nick |
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