Lowering the PSU noise

[jema]

Got a lovely 400W PSU (of unknown brand so it may not be so good after all, but hey atleast it says 400) with the distinctive trait that it is LOUD. The fan in the PSU does 3500RPM so my plan to lower the noise is to:
1- Exchange the fan for one with lower RPM and put another low RPM one in front blowing air into the PSU.
2- Put a dust cover on the air intake for the PSU that will lower the air flow and thus the noise.

Im not completely at ease with either solution, the first because it is really stupid to tinker with the PSU and nr2 because I might cook the PSU by lowering the airflow any fry the fan by making it work harder.

Prehaps a RPM controller would do the trick? Never tried one of those.

Yes I could buy a quiet PSU but I dont feel like it. Ideas suggestions and hints welcome.

 

[chopstxxx]

Changing the fans in your PSU shouldn't be a very big problem. Just make sure to discharge it and to don't touch any caps while you're changing the fans. As for the filter I doubt it will quiet the noise, it may even make it louder because as you said, the fan will have to work harder and the filter will also increase turbulence. Contolling the RPM's is a decent idea as well, Enermax makes a PSU with a manually adjustable fan in it. Hope this helps a little.

 

[jema]

Found an Enermax fan that looks good, UC-8FAB, think I'll give it a try.

How do I discharge the PSU? Just let it sitt unplugged for a day or something more complex?

 

[Pothead]

just don't touch the capicitors or we will be losing a member! The UC-8FAB seems to be fairly weak moving out very little air when I had it set at the slowest speed setting but the enermax adjustable PSUs use these fans. A lot of members replace the psu fan with a panaflo 1la.

 

[trikster2]

I did the PSU mod, swapping my loud PSU fan for a panaflo L1A but now regret it.

Say for example: My house burns down and it's trace to my hacked/now-non-UL listed PSU. Wonder if insurance will cover it?

 

[jema]

And how are they going to figure that out? If you do good work and nice soldering they shouldnt be able to tell.

Is there any good way of measuring the temp inside the PSU?

 

[jema]

*bump*

 

[MiloMinderbinder]

If there is any "flat" sheetmetal (such as a finger guard) near the blades of the fan, make sure that there is some clearance between the blades and the metal. The shear effect from a blade passing close to a stationary surface generates a lot of noise. Round finger guards are generally not a problem, unless they're very close to the blades.

Fans cause the power supply case to vibrate, which adds noise. Try mounting the fan with some rubber gasketing material between the fan body and the metal.

To discharge the power supply, just shutdown your PC normally. Then toggle the switch on the power supply itself from "1" to 0". Wait 30 seconds, then disconnect the AC power cord from the supply. All done - you can take the supply out and be perfectly safe.

Don't worry about burning down your house. You would have to short directly across the supply's internal AC connections (which are shrouded, btw) with something heavy, like a screwdriver. Then you'd have to put the supply cover back on, making sure that the screwdriver didn't shift position. Then you'd have to plug in the AC cord while ignoring the heat right next to your hand, the suddenly hot cable, and the lights dimming. Then you'd have to run outside to the fuse box and keep swapping in higher rated fuses or circuit breakers until you found one that wouldn't shut down the circuit. THEN you can get out the marshmallows.

Scotty

PS AFAIK, New York City is still the only municipality in the US that requires UL approval on electrical equipment sold. Approval carries no weight anywhere else in the country, and confers no benefits. Most retailers require UL approval before they'll sell something, but you won't get into trouble with your insurance company for using non-UL equipment (within reason).

 

[AT]

Originally posted by: MiloMinderbinder

To discharge the power supply, just shutdown your PC normally. Then toggle the switch on the power supply itself from "1" to 0". Wait 30 seconds, then disconnect the AC power cord from the supply. All done - you can take the supply out and be perfectly safe.

I have to wonder if this is true. I have always been led to believe that the capacitors in a computer power supply will remain charged for a few days unless discharged with special equipment. And there's a lot electricity in those capacitors.

 

[jema]

Thanks Milo.

The PSU fan is mounted right smack on the back plane of the PSU case (something that seems like "standard") so if I wanted to remove air cavity noise Id have to cut out some of the metal there and while I doesnt feel to good about that one could however open it up a little, hm... Well thank you all people I now have some ideas to work with.

Still does anyone know how to measure the temp inside a PSU?

The capacitators aint that big, call again when you found a comp with the soda can sized ones in it
Honestly though (and all AFAIK) I think that there is some connection between voltage and remaining charge, a TV tube will hold its charge for some time but has close to 10 000V in it (and it HURTS if you put your fingers in the wrong place, belive me) while lower voltage components will loose their charge quite quick.

 

[Mday]

Originally posted by: trikster2
I did the PSU mod, swapping my loud PSU fan for a panaflo L1A but now regret it.

Say for example: My house burns down and it's trace to my hacked/now-non-UL listed PSU. Wonder if insurance will cover it?

if your house burns down, and it is tracked down to the PSU, they wont know that you modded it... the fan would be long melted etc...

 

[MercenaryForHire]

Originally posted by: AT
I have to wonder if this is true. I have always been led to believe that the capacitors in a computer power supply will remain charged for a few days unless discharged with special equipment. And there's a lot electricity in those capacitors.

Damn right they will ... same thing as monitors, they're nasty. Taking a 250W discharge up my left arm was not a pleasurable experience. Use chopsticks or something else nonconductive. Some recent PSs have simple plug-fans, 2 or 3-pin models that can be swapped out in a skipped heartbeat. If not, just be careful.

- M4H

 

[MiloMinderbinder]

The PC power supply consists of three basic circuits: primary side, secondary side, and standby. The primary side stores some charge at the rectified line voltage (~155V in the US), the secondary side stores charge at the rail voltages (+5, +12, etc), and the standby circuit stores charge at 5 Volts.

When you shutdown your operating system and the power supply shuts down, the modulator (which generates the secondary side voldages) turns off. This means that all of the rail voltages decay quickly to zero.

When you flip the switch on the back of the supply, you disconnect the supply from the AC mains entirely. This means that the primary side storage is no longer getting charged. The primary side storage supplies the standby circuit, and so the primary side storage bleeds off through that. It also has bleed resistors to drain off any residual charge.

Five seconds after flipping the switch, the only voltage in the system is what the motors in the drives are generating as back-EMF. Wait the 30 seconds for them to spin down and you've got a completely discharged supply.

Working on monitors is different. Monitors have a flyback transformer that stores charge in a tight magnetic field and there are often no bleed resistors on the load. Turn off a monitor and unplug the power cord, and you still have a stong field in the transformer. Put a conductor (like your arm) across either side of the flyback, the field collapses and you get a nice big zap. Flybacks are nothing to fool with - big ones can operate at thousands of volts.

Scotty