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Old 01-15-07, 09:22 AM   #1
phantomcow2
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What will happen if I let this bridge rectifier keep smoking?

So I just put 39vAC into an old bridge rectifier. I connect bridge rectifier to three 10,000uF capacitors in parallel. As soon as I supply power, I see smoke. I disconnect capacitors, capacitors appear to be fine. But rectifier is spewing out smoke, not sure why. It is rated for 400v and 25amps. It is probably 18 years old though. The transfer was making odd sounds while the rectifier was smoking; almost like a stalling motor. THis is what made me unplug the power. So, what will happen if I leave it plugged in?
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Old 01-15-07, 09:25 AM   #2
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It might get lung cancer.


...........or YOU might.......
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Please dont outsmart the censor. That is a very expensive censor and every time one of you guys outsmart it it makes someone at the home office feel bad. We dont wanna do that. So dont cleverly disguise bad words.
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Old 01-15-07, 09:28 AM   #3
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I have an acrylic enclosure for a lathe, perhaps I should place the rectifier inside and find out?
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Old 01-15-07, 09:30 AM   #4
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Originally Posted by Siu Blue Wind
It might get lung cancer.


...........or YOU might.......
My thoughts exactly!
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Old 01-15-07, 09:33 AM   #5
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Quote:
Originally Posted by phantomcow2
So I just put 39vAC into an old bridge rectifier. I connect bridge rectifier to three 10,000uF capacitors in parallel. As soon as I supply power, I see smoke. I disconnect capacitors, capacitors appear to be fine. But rectifier is spewing out smoke, not sure why. It is rated for 400v and 25amps. It is probably 18 years old though. The transfer was making odd sounds while the rectifier was smoking; almost like a stalling motor. THis is what made me unplug the power. So, what will happen if I leave it plugged in?
The rectifier is probably fried
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Old 01-15-07, 09:34 AM   #6
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You know, I never understand Phantom's threads but I still keep clicking on them.
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Please dont outsmart the censor. That is a very expensive censor and every time one of you guys outsmart it it makes someone at the home office feel bad. We dont wanna do that. So dont cleverly disguise bad words.
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Old 01-15-07, 09:42 AM   #7
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Kinda like...



Because you like pancakes.
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Old 01-15-07, 09:54 AM   #8
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it will let all the smoke out and quit working
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Old 01-15-07, 09:56 AM   #9
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Yeah once you let the magic smoke out, things quit working.

And sometimes those big guys with the big noisy trucks come and visit.
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Old 01-15-07, 11:44 PM   #10
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I love the smell of PCBs in the morning................
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Old 01-16-07, 12:13 AM   #11
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Give it the patch
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Old 01-16-07, 12:15 AM   #12
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Quote:
Originally Posted by phantomcow2
So I just put 39vAC into an old bridge rectifier. I connect bridge rectifier to three 10,000uF capacitors in parallel. As soon as I supply power, I see smoke. I disconnect capacitors, capacitors appear to be fine. But rectifier is spewing out smoke, not sure why. It is rated for 400v and 25amps. It is probably 18 years old though. The transfer was making odd sounds while the rectifier was smoking; almost like a stalling motor. THis is what made me unplug the power. So, what will happen if I leave it plugged in?
Hmmm, assuming all the diodes in the bridge are OK, the caps should have charged up to the peak value of the AC signal since you have no DC load to discharge them. Maybe one of the caps is bad ( internal short ), or maybe one of the rectifier diodes is shorted. Anyway, the fire is due to something drawing excess current, so it will continue to burn until whatever component is drawing excess current burns up and becomes an open circuit. And along the way, it will stink real bad.
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Old 01-16-07, 12:24 AM   #13
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Is it a plasticy smell, or ozone? I'm wondering myself if its a cap's dielectric that is burning (and that stuff is bad to inhale.)

Nothing lasts forever; I'd consider replacing the FWBR and/or looking at the step-down transformer.
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Old 01-16-07, 12:38 AM   #14
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Was there a load on the circuit? Are you sure you weren't overamping it?
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Old 01-16-07, 01:14 AM   #15
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I betcha the caps are on backwards.... give us a schematic of your circuit, eh?

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Old 01-16-07, 04:58 AM   #16
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Quote:
Originally Posted by icithecat
I love the smell of PCBs in the morning................
+1. We removed some PCB filled 12kV capacitors a few years ago after one ruptured in a substation. I think it was the combination of the PCB's and the burning oil. We all should get to experience said stench.
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Old 01-16-07, 05:52 AM   #17
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Basically, here is how it all went:

Have one transformer, with a 39vAC output. 116 input. -39volt output goes to the bridge rectifier, approx 36 volt output from the rectifier. The negative and positive will be connected appropriately to three 10,000uF capacitors in parallel. Then, there will be a 2kohm 1W bleed resistor connecting - and + at the end. I will probably stick a few fuses in there too.
I am not too disappointed though. THese rectifiers are close to 20 years old, they have lived a prosperous life. Radioshack sells one that is 400v @ 6A. My load is not even 2A. The capacitors and transformer are professionally mounted on an original case, I know they are okay.
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Old 01-16-07, 05:54 AM   #18
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Also,
I saw the images my friend got when he tested the output of his identical rectifier with is 'scope. The best way I would describe it, is 15/16 wave rectification.
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Old 01-16-07, 07:43 AM   #19
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I think you need tosubmerge the apparatus in water to cool it down.
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Old 01-16-07, 09:22 AM   #20
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I think you need tosubmerge the apparatus in water to cool it down.
+1 Bath water is good for this. You will have more control of the process if you are in the tub with the electronics. The other nice thing about the water bath cooling method is watching the smoke filled bubbles pop as they rise to the surface. Have Fun!
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Old 01-16-07, 09:27 AM   #21
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Quote:
Originally Posted by phantomcow2
15/16 wave rectification.


That might be useful in some VERY niche projects...
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Old 01-16-07, 10:43 AM   #22
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If the recitfier has diodes in it...I bet that you popped one or two of them. Leaving it connected might frey the rest of them. A schematic of your setup and the rectifier would be more insightful.
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Old 01-16-07, 12:15 PM   #23
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Basically this:

The Seven Plagues
1. Ugly and painful sores will break out on the people who have the mark of the beast and worship his image.
2. The sea will turn into blood like that of a dead man, and every living thing in the sea will die.
3. Rivers & springs will become blood.
4. The sun will scorch people with fire.
5. The kingdom of the beast will plunge into darkness. Men will gnaw their tongues in agony and curse the God of heaven because of their pains and their sores, but they will refuse to repent of what they have done.
6. The great river Euphrates will dry up to prepare the way for the kings from the East.
7. Cities and countries will collapse and huge hailstones of about a hundred pounds each will fall from the sky upon men, and they will curse God on account of the plague of hail, because the plague will be so terrible.

OR

It will just break and be rendered useless.
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