How much should I reduce the fan speed for my psu?

[saitrix]

Hi,

For my htpc I run laptop components with an amd 4350, I estimate the pc uses no more than 150w under load, probably less. The case I bought for it came with a 400w(!) sff psu. So I am not pushing the psu at all. Annoyingly that psu is also the loudest thing, so I opened it up. I found it had an 80mm fan, it didn't have a speed rating but it does say it draws 0.2a if that helps. I was thinking about running it at either 5v or 7v by swapping the wires that power it. Does this sound sensible? The psu intakes air from outside too so should have good intake temps.

[Ksanderash]

Go on! ) Air blow from the outside should be slightly warm, then it's OK. Make sure the fan starts firmly on low voltage. If it doesn't -- you take risk )

But I think it's better to buy a 120mm fan equipped PSU.

[quest_for_silence]

I was thinking about running it at either 5v or 7v by swapping the wires that power it. Does this sound sensible? The psu intakes air from outside too so should have good intake temps.

Afaik, without knowing how much you will reduce its nominal rpm, it's not easy to foretell: I can tell you that with similar loads, a 80mm fan running constantly around 700rpm should suffice.

But is it a 2 or 3 pin fan? If it's a 3 pin one, maybe you could drive the wires outside up to a motherboard fan header.

[saitrix]

Well I have done the mod to 7v and it is perfectly fine. Unfortunately it still isn't as quiet as I'd like, and the fan only has 2 wires so no rpm monitoring. Think I may swap the fan for an aftermarket 80mm fan and like you say, run it ~700rpm.

Ksanderash, Unfortunately a 120mm itself is wider than the case it is in!