Is it safe to replace PSU fan?

[Ben_107]

Hi,

I have an Acer SFF computer with a TFX PSU, which has a very noisy fan. I would like to attempt to replace the PSU fan. I have had the computer off for about two weeks now. My question is, would the capacitors be safely discharged after this period, in order for me to be able to safely open the PSU? Any other advice for safely working on a PSU?

Many thanks.

 

[ingtar33]

it can be done, but working on a PSU is NOT SAFE in any way whatsoever. The capacitors can store a lethal amount of electricity for years. I did it once myself, scared myself silly, but I know it's doable.

I suggest you simply buy a new one. Its not worth the risk.

 

[joex444]

I'll second that, it can be done but it isn't meant to be done by the end-user. The capacitors do store a lot of energy and can be lethal if you mess up.

If you've only had your PC off for 2 weeks, the capacitors are charged. You need to have it disconnected from the outlet, and even then I would try holding the power button to make the PSU give up the last of its charge trying to power things on.

Inside a PSU there are basically only two kinds of connections for the fan. One is where the fan is hard-wired into the PCB. The other is where it's a standard 3-pin fan. With the latter, the replacement is straight-forward. With the former, if you feel comfortable the correct way would be to desolder the fan connection, remove the connector from the new fan and solder it into the PCB. A more hackish way would be to cut the leads for both fans, join them with a proper splice, put caps on them, and then tape/zip tie the wires into place so they don't interfere.

 

[CelicaGT]

There are balance and bleeder resistors in place to drain the caps. Use a meter to determine when the array is safe.

 

[Ben_107]

Thanks to everyone, I really appreciate the replies. I think I will follow your advice and just replace the PSU. However, I am really struggling to find a TFX PSU that will fit the Acer case. I live in the UK, so any links to a replacement PSU at a reasonable price would be really appreciated.

Thanks again,

Ben

 

[thx1138v2]

I just cleaned the inside of mine two days ago. Most modern circuits have what are called "bleed resistors" to bleed off the charge after the power is removed. The last time I saw any dangerous capacitors was when I scrapped out some old analog radios and TVs. So the danger level would partly be determined by the quality of the PSU.

You have enough knowledge to ask so I'm guessing you know how to be careful, e.g. removing power cord, use gloves, and don't use any metal tools once you get it open, etc. It partly depends on how the cover comes off. The cover on my Antec PSU covered the top and bottom of the circuit board so both were exposed once the cover was removed. It would be necessary to expose the bottom to bleed the capacitors.

You can bleed them yourself if need be. Just use a heavy piece of insulated wire,14WAG or 12AWG, and touch the ends of the wire to the leads of the capacitor while holding it by the insulation. Or if you have a high resistance capacitor (10 megohm, 1 watt or better) you can use that to bleed them.

I didn't bother. I just used plastic tools and Q-Tips to do my cleaning and had no problems.

BTW, my fan had a plug-in connector but your fan's leads might be soldered to the circuit board. That will get into desoldering/soldering so if you're not handy with a soldering iron it might be better to just buy a new one if you can afford it.

 

[Ben_107]

Thanks for your reply. I'm afraid I don't have the confidence or the skill to discharge capacitors. However, if I follow your safety precautions, would I be ok just to open the PSU case and check to see if the fan did have a pin connection? If it was soldered to the board, I think that I would just buy a new PSU.

Thanks,
Ben

 

[toyftw]

it can be done, but working on a PSU is NOT SAFE in any way whatsoever. The capacitors can store a lethal amount of electricity for years. I did it once myself, scared myself silly, but I know it's doable.

I suggest you simply buy a new one. Its not worth the risk.

AGREED!

 

[Ben_107]

Thanks to everyone, I will definitely not attempt the repair myself!