Taking apart a power supply

entropy

I thought this would be common... but a few searches yielded no decent results.

Anyway. How easy and/or stupid is this? I seem to recall rumblings in various posts about how dangerous it is (and I don't doubt it). Is there any way to totally discharge the PSU? My thought would be, power down, wait a few minutes. Flip the switch to off, hit the power button (it always goes for a second or so). Unplug it, switch to on, power button, off, power button. Sounds excessive, but hell, I don't want to be zapped by who-knows-how-many watts are stored in that thing.

With any luck I won't have to cut wires. Unless the fans are hardwired in, in which case I'll be snipping a bit. It's just the thought of prodding around in there that spooks me. I want to replace the fans with some Vantec Stealth ones that were recently mentioned (very quiet, and move decent enough air). The current ones are noisy and don't do crap (hardly any movement, hot PSU case). If these fans are hardwired, is it possible that they're thermally controlled? It's an Ultra 500w from before Ultra was good at anything. It's stable enough, but it wasn't "known."

So yeah - recap, since I sort of rambled on there.

• How dangerous is it to futz around inside a power supply?
• How do I force most of the power out of it beforehand?
• Is it possible that these fans are specially designed for this power supply, and any others would overload it or something?

Thanks once again

profdlp

entropy wrote:

...

• How dangerous is it to futz around inside a power supply?

Electricity is always to be respected. If you are careful not to just grab things willy-nilly, are focused enough to not get distracted and brush up against something you shouldn't, and discharge the capacitors beforehand you should be alright. Wearing some rubber gloves is not a bad idea, either. The kind they sell at the grocery store so you don't get "dishpan hands" ought to do it.

• How do I force most of the power out of it beforehand?

I bend a 6" piece of heavy gauge insulated solid copper wire (not stranded) into a U shape, strip about 3/4" of the insulation off each end, then hold it in the middle with a pair of linesman's pliers with an insulated grip. Then use that to short each leg of every capacitor to ground. I use a spare power cord with the hot and neutral prongs busted off, plugging one end into the power supply and the other end into the wall, giving me a solid ground at the casing of the PSU.

• Is it possible that these fans are specially designed for this power supply, and any others would overload it or something?

Extremely unlikely, unless you've got some exotic PSU. The old fan will almost certainly be hardwired into the unit. Just have your soldering iron handy and don't forget to slide a sturdy barrel insulator over each wire before you hook them together. I don't like to use crimp on connectors by themselves, much less electrical tape. It gets warm in there and you don't want the works coming apart, shorting everything out, and maybe taking your whole rig with it.

muddocktor

I do it all the time and if you are reasonably careful, it's no problem. Prof listed quite a few things to do but I have seen some psu's that have a fan connector on the circuit board, but they aren't a normal 3 pin mobo connector and are usually a smaller type that is just 2 wire. Most are directly soldered to the board though. On the one's that are soldered, I just cut the leads high enough up to give me good working room. I solder the wire leads together and use heat shrink tubing to cover the soldered connection when I change out a fan in a psu for insulating the soldered joint. Another trick to help psu ventilation out is if the fan hole on the back uses a stamped hole in the psu case for finger guard protection is to cut it out with a dremel and use a wire fan guard, which gives much less resistance to airflow.

entropy

Thanks for all the tips, guys! Prof, that looks to be about the safest way to go about this, great ideas. The only problem is, I don't have all those tools at the ready, and I could get/make them, but for how often I plan on doing this, it doesn't seem worth it. However. Out of curiosity today, I took it apart. Just popped off the top, not totally disassembled it. Few things I noticed. Holy frick that's a LOT of dust. I blew it all out (compressed air) to begin with, then looked around. Some good and some bad.

1) One fan, the rear one, is very easy to get to, which is good. Also, it happens to be that that's the one that connects via pins to the board in the PSU. Definite plus.

2) The front fan, however, is near impossible to get to. I'd have to unmount that board, then shuffle stuff, THEN unscrew it. Not fun. But maybe necessary. And then cut and mend the wires to the new fan, as that one is hardwired.

Really cool thing: the fans are quieter. I think that back one, the one with the pin, is thermally monitored, and the dust made the PSU hotter, so made the fan spin faster to compensate. And the PSU is only putting out barely-warm air, as opposed to very-warm.