Is There Anything In Here That Can Kill Me??

[Adji]

Okay, this PC power supply broke a few days ago and has been replaced. I thought I may be able to use the box / some of the parts for something cool in the future. Just wondering if I take this apart is there anything in there that can hurt me? There are some pretty beasty looking Electro Caps in there.

Stuff like the big caps, IEC jack, power switch, fan, box etc all could come in cool for something?

[R.G.]

That *can* kill you? YES!!

That thing takes the EC power line and rectifies it to between 180 and 360Vdc, then stores it in some of those big caps. The charge is somewhat reduced when it's powered off, but it can hold charge for quite a while under  some circumstances.  If it's been plugged into the AC power line in less than a month or so, I would advise extreme caution. It's rare for this to be a problem, but some internal failures can make it hold a charge.

There are ways to make it safe as you go, but they all involve you working inside it to discharge the caps safely. There is some risk.

[Adji]

RG to the rescue again hehe.

Cheers mate. You recommend I leave it for a couple of months before opening it up? Or is there an idiot-proof way of discharging those caps? I head something involving a screwdriver or something once?

Actually, probably best to go ahead and leave it for a few months hah.

[petemoore]

  Actually you want to measure 0.0vdc across the cap, after having drained it.
  Time tends to drain or charge a capacitor sitting ''there'', static electricity doesn't have much amperage, but 20,000volts charge is pretty easy to get generated using houshold items such as carpet and another material, worth a study in itself to dislodge my rambling off topic.
  I use a fat [10watt or fatter] resistor with some 'smoke tape' [electrical tape] around it, 22k is what I choose, doesn't spark and drains the V down to 1/2 generally in a few seconds.
  IIUC, which is questionable since I chose not to play with these very much, opting for linear power supplies, there are a number of isolated HV sections to these supplies, making sure they are all discharged on a one-off basis [having to familiarize yourself with the topology etc., in an effort to hit each section] means handling the dern unit, ?use rubber gloves...they don't exactly have handles.
  It is possible to use WW's to get those voltages, regulators for ripple free
DC, probably no larger or weighty than the SMPS unit.

[R.G.]

  Actually you want to measure 0.0vdc across the cap, after having drained it.
  Time tends to drain or charge a capacitor sitting ''there'', static electricity doesn't have much amperage, but 20,000volts charge is pretty easy to get generated using houshold items such as carpet and another material, worth a study in itself to dislodge my rambling off topic.
  I use a fat [10watt or fatter] resistor with some 'smoke tape' [electrical tape] around it, 22k is what I choose, doesn't spark and drains the V down to 1/2 generally in a few seconds.
  IIUC, which is questionable since I chose not to play with these very much, opting for linear power supplies, there are a number of isolated HV sections to these supplies, making sure they are all discharged on a one-off basis [having to familiarize yourself with the topology etc., in an effort to hit each section] means handling the dern unit, ?use rubber gloves...they don't exactly have handles.

All good material. I'm being extra cautious in my advice: I want you not to get hurt under any circumstances.

There is generally at least one person who reads my advice like this and pops in with "Well, we used to do that all the time and twice on Sundays and we never got shocked." Which is probably true. But there are rare circumstances which would leave them hot. And "rare" is no comfort at all to your widow.

Pete is correct, you can discharge them with an insulated lead and a resistor. The problem is that you have to work with the insides of the power supply with screwdrivers and so on for a while to get at the leads, since they're almost universally only available on the bottom of the PCB. And you can work carefully, wear rubber gloves, stand on a rubber mat, use plastic handled tools, keep one hand in your pocket (to keep it from making a path for the current through your chest), all this and more. But still...

[Derringer]

FWIW, I'm a big fan of computer power-supply enclosures

no pics yet, but I've just about wrapped up a splitter-blend with an switchable LFO to wiggle the blend inside of a power supply box ... in true form to the splitter blend I suppose


Just keep your head about you when you're taking the thing apart. Of the two that I've gutted and used, I was able to get the insides out without having to come anywhere near touching something inside that was potentially harmful

[G. Hoffman]

If you know what the circuit needs to look like, you can usually find places to discharge from the top side of the board, but it can be pretty difficult sometimes - they are packed pretty dang tight! 

Honestly, most of the active electronic components are pretty hard to find a use for.  The switches and IEC are nice, though, and in the two I've opened up, I was able to salvage some killer heat sinks for TO-220 regulators.  I built a really nice ±15V cascading power supply - it turns out I don't actually need it for anything, but whatever - using one of the big heat sinks, and I've used the smaller ones on a variety of other power supplies.


Gabriel

[petemoore]

  Here's an idea, only an idea..
  Dip it in water for a while ?

[R.G.]

  Here's an idea, only an idea..
  Dip it in water for a while ?

You know, that would work.

Being dipped in water is not necessarily fatal to electronics; only the failure to get the water out afterwards and the ensuing corrosion is. In fact, some manufacturers did use modified dishwashers to clean circuit boards way back. They were careful to blow the water off with compressed air and dry them in a warm air bath to get the water out. Anything not promptly dried would corrode, but then if what you want is the box, connectors, etc., that's not a big problem.

This is almost a corollary to salvaging either the parts or the PCB. If you never need the PCB to work again, you're less worried about the water.

[Adji]

Well after reading all of this I think I better just leave it haha. I have never worked with anything above 9vDC and have no idea on draining the caps and stuff. I think I hsould probably just leave it to be honest?

[GibsonGM]

Good call if your instincts tell you to do that; that's what they're there for!

[MikeH]

  Here's an idea, only an idea..
  Dip it in water for a while ?

Yeah, if all you want is the enclosure, that would be a great way to go.  Probably shouldn't do it while you're taking a bath.

Really, the only thing that you need to worry about are the filter caps, or really any electrolytic that has a voltage rating on it over 25V or so (to be safe)  Find those caps and measure the DC on them with the HV setting on your DMM.  You will most likely find there is no charge.  I've used PC power supplies to salvage fans, AC plugs, heatsinks, sometimes the enclosures, and I've never found one with a charge in it.  Mostly I find them to be full of filth.  Like, just packed with dirt and dust.  Ugh.  More of a threat on your allergies than anything else.