I have a 250w Fortron PSU (passive PFC, thermistor controled fan, can't remember the exact model but it's similar to this one), and two problems :

- There is a big coil inside the PSU that buzzes and vibrates. I soft-mounted it using rubber pieces and earplugs, and the vibrations don't transmit to the case anymore, but I can still hear the buzz through the acoustic foam.

- The coil began to whine yesterday's night.

Of course i've been searching for a solution through the forum, as I know coil whine and coil buzzing have both been discussed very often here, but I still have a few questions :

1°) I can't find that "special lacquer", that's designed for coils. Is there something else I could use to prevent the coil from whining and that I could find easily ? Nail polish ? Glue ?

2°) Would lacquer/varnish/whatever also prevent it from buzzing/vibrating ? And if not, what could ?

3°) I have a non-PFC PSU at home, and it doesn't have a coil, or at least, not such a big one. Could it be that this coil is related to PFC ? I'm just wondering.

Thanks !

Well I read you could try wooden toothpicks between the windings - didn't work for me. Also I tried an epoxy glue 'coat' - also didn't work for me.
I would stake a large sum of money it is a choke for the PFC circuit.
- My FSP 300-60BT has one of these (bolted and now grommeted to the lid of the psu case) - I never could silence it so retired the psu to one of my noisier systems.
- A Jou Jye psu I got had active PFC: instead of the large choke it had a daughter card with several components including a coil on a donut ferite core that buzzed. This is the one I tried to sort (without success) with toothpicks & epoxy. Fortunately the psu blew up and I threw it away.
- A Mercury (aka Deer) passive PFC I have also has the large choke mounted on the psu lid as per my FSP. I have also failed to silence this one.
- My current psu is a Powerup (aka Deer) with no PFC, and is silent.

In my experience PFC costs money as well as noise - I hope I have to eat my words at some stage in the future but (on the noise front) I am disillusioned with PFC! But hey, hopefully someone else here can enlighten us how to silence these damn things

What kind of noise do PFC ???

On the other hand, it looks like the commonality among your PSUs is either lower quality brands or passive PFC, not just PFC. I have rarely experienced any buzz/whine problem with APFC units from Seasonic, and none so far with the Nexus, SilenX, or Fortron 400w APFC units. The Zalman 300W APFC sample is another story, it's a whiner, but this is already documented -- by jinu117(?), I believe -- as a flaw Zalman has owned up to.

- well certainly downright cheap

Previous to my FSP I doubt any of my psu's had any PFC: the only one that was quiet was a brilliant Seventeam 235W that is still running for a relative. I do hope it is just coincidental/personal to me: I remember (over 18 months ago) planning & researching for weeks with PFC as a number 1 'must have', and eventually finding my FSP for quite a premium ££. It really is a Jekyll & Hyde PC - built like a tank, reliable as the best, and performs like all the reviews say it should. But the noise has been a battle I lost: started with fans, put a Papst on grommets, still had noise, eventually ran it open 1 day without a fan and discovered what electronic noise was! It may well be a close cousin of the Zalman 300W?

And for me the perfect irony is that the absolute cheapest psu I have ever bought is electronically silent.

But OK, I hope I am the exception and one day will buy another 'quality' psu. Already I dread the process: what shop can you go into and ask to see the design inside the psu, and to listen to at "1am suburbia" levels of background noise! I guess thats what SPCR reviews are for

Also I am 'contrary' about the current trend for 350/400/450/500W psus - I only need 100-200W and want to be on the high end of the psu's AC/DC conversion efficiency curve, not in the pits! The fanless FSP 200-5P01 is tantalising - the bad news is that it has missed its Q1 launch by a long way And the longer my current Deer runs stable & quiet the more contrary I will be! (Then again, 1 small fire will have me back on the straight and narrow!!)

Ok, thanks. Looks like there isn't much I can do.

I couldn't put up with the noise, so I put my 120mm fortron (PF) back in, and it's much better. With the cpu ducted and the thermistor a few millimeters away from the heatsink, it doesn't speed up too much. And at least it doesn't whine !

Another PSU-related question now, is it possible to trick the thermistor in the 120mm fortron into thinking the temperature is lower ? Assuming the fan controler is linear, but there is a minimum voltage that is fed to the fan when the temperature is below a certain value, then just tricking the thermistor into thinking that the temperature is 5°c or 10°c lower would turn the controler into some kind of "two stages" device : the fan would only speed up under high loads, and would stay slow in normal use.

Would soldering a resistor inline with the thermistor do that ?