| demogorgon |
hello!
my rectifier board with 8 mur1520 diodes stopped working after i installed bypass diodes to take care of diode ringing.
I measure voltage into the board, but nothing out of it.
i put the caps in paralell with the diodes. they are 0.15uf 63V devices, polypropylen i think.
what have i don wrong? :cannotbe:
regards
marius |
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| peranders |
| .... the soldering, maybe. I suggest that you check the connections once more. Do you have any AC voltage into the rectifier? |
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| demogorgon |
i checked all the connections, they are all correct.
Yes, AC in to the rectifier, dead/nothing out. |
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| peranders |
| Have you checked the diodes with a DVM? Do have have any voltage across the diodes? How many volts across the AC inputs of the bridge? |
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| demogorgon |
DVM?
and volt across the diodes? well i would guess so, considering that they manage to create ground. so at least four of the eight..
17.8V ac across the inputt
thank's for helping!
marius |
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| peranders |
... you don't guess, you have to know. Just measure! If you don't have experienced any smokeand blown fuses I'll doubt that you have broken the diodes. You carefully and nice have soldered in caps in parallel of the diodes and now nothing is working. You can actually use DVM and the "diode test" and check the diodes. You should get 0.5-0.7 volt in forward direction and much higher in the reverse direction, not necessarilly 1.999 if the bridge is connected.
You should also check you wiring. |
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| digi01 |
| quote: | Originally posted by demogorgon
hello!
my rectifier board with 8 mur1520 diodes stopped working after i installed bypass diodes to take care of diode ringing. |
before you installed bypass caps,what about the rectifier runing? |
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| Nuuk |
| Would he need to connect a load to measure the bridge? |
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| Markje |
If you connect a load, it will finfluence your measurement. If you measure diodes, the best way is to desolder them, otherwise, you should measure what peranders is saying, .5 to .7 in one way and something else in the other way (depending on the diode you are measuring).
Greetz Mark |
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| peranders |
| You can do pretty good troubleshooting also when the diodes are connected. |
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| demogorgon |
| quote: | Originally posted by peranders
... you don't guess, you have to know. Just measure! If you don't have experienced any smokeand blown fuses I'll doubt that you have broken the diodes. You carefully and nice have soldered in caps in parallel of the diodes and now nothing is working. You can actually use DVM and the "diode test" and check the diodes. You should get 0.5-0.7 volt in forward direction and much higher in the reverse direction, not necessarilly 1.999 if the bridge is connected.
You should also check you wiring. |
I know there are voltage on the inputt of the diode bridge.
no fuses blown as of yet. i do however use 10amp auto fuses, like the ones you find in on your main household wiering. they are nice to use when you don really know what to exspect.
Well, as i said, the diodes filter out ground at the very least, otherwise i wouldn't have much of a refference point for measuring voltage. and i know it works because i tested one pin to ground and the other to one of the phases on teh main wiering, and it was 135V as it always have been.
The wiering is checked, prepped and a-ok.
| quote: | Originally posted by digi01
before you installed bypass caps,what about the rectifier runing? |
it worked like a charm. my GC had been playing music for two weeks straight.
thanks for all the help and input guys!
cheers
marius |
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| peranders |
Have you checked every diode with "diode test"?
Maybe you could take a photo? |
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| macboy |
| If you have no load and no filter caps connected to the rectifier, then the bypass caps will do just that... bypass the AC right across the diodes. If the caps are all the same in value, you have created a nice balanced 'wheatstone bridge' and you will measure 0 volts at the outputs. You need to load the output of the rectifiers so that current will flow through the diodes rather than just through the bypass caps! |
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| peranders |
| You may be right on target :idea: I never thought that demogorgon had a completely unconnected bridge. |
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| demogorgon |
| quote: | Originally posted by macboy
If you have no load and no filter caps connected to the rectifier, then the bypass caps will do just that... bypass the AC right across the diodes. If the caps are all the same in value, you have created a nice balanced 'wheatstone bridge' and you will measure 0 volts at the outputs. You need to load the output of the rectifiers so that current will flow through the diodes rather than just through the bypass caps! |
You are totally right.
how humiliating..:sorry:
thanks for helpng me out here anyways.
cheers
marius |
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| peranders |
1 Have I measured on a design without the power switch on?
2 Have I measured with broken oscilloscope probes?
Right answer:
1 :nod:
2 :nod: |
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| Nuuk |
| I'll come clean too! I only suggested that because I measured a bridge that I built without it being connected to anything and also got a reading of 0 volts! :cannotbe: |
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| demogorgon |
Hehe, we all do mistakes every once in a while i guess, but then, i had no idea that i would get this effect of bypassing. now at least i know better, and so this will not be reppeated.
regards
marius |
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| peranders |
| It's wonderful to see the light :idea: and laugh to ones mistakes. :cannotbe: :nod: |
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| Markje |
Whoops. Never thought of that. Dumbdumbdumd.
Greetz Mark |
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