Sergio T.P. wrote:
> Hi all.
>
> I've bought a new 400 W power suply. It was supposed to be a silence power
> suply. In fact, it is less noisy than my old one,

actually that is to be expected. Higher wattage is supposed to be less
noisy. The logic is that it can produce up to 400w because it is more
efficient in that it producese less heat, so has less heat to remove.
(so the fans needn't spin as fast).

Maybe if the 400w PSU was also operating at 400w then it could be as
loud as a 300w (operating at 300w). But I guess typically the 400w PSU
won't be using all 400w. Especially not in a computer that ran with a
300w.
If you require 300w , then I guess whether you put a 300w or a 500w or
a 700w PSU in there, you'll get 300w. 400w is better though, less
strain on the PSU in intensive times.

> but when I turn on the
> compueter it makes a lot of noise... It's not a regular noise, like the
> noise of a fan. It's some kind of tickling sound... In 3 / 4 minutes it goes
> lower untill it gets the normal level of noise of the power supply.
> Sometimes the noise disappears when I lift a bit the case and let it down
> again, or if I shake a bit the case...
> Extrange thing is that I had exactly the same problem with my OLD power
> supply... (high sound when switching on).
>
> It that normal?? perhaps it sounds untill it warm up or something??
>

you have to narrow this down. It's important that you sort of found a
trigger. THe defeault position causes the noise. But lifting the case a
bit stops the noise.

try taking the power supply out of the case. If it makes a noise then,
it's easy to narrow down. If it doesn't make a noise, great. Put it
in the case, turn it on, see if there is a noise. If so, take it out,
or move it somehow, put it in a bit differently.

A friend had a similar problem, I think with the power supply. We
found that putting some tissue paper between the power supply and the
case stopped the noise. Maybe it secured it better and stopped the
vibrations.

Lifting the case is causing some other changes that are stopping the
noise. So you have to experiment with moving things, holding things,
not holding things, squeezing things. Move PSU from a position where
there is noise(screwed in case as it is currently), to a position where
there is no noise, finding the dfiferent ways. Move from a position of
no noise(e.g. psu out of case), gradually trying to secure the psu,
until yju suddenly find noise, then you've foudn a trigger. Hold it in
place with your hand in te air. Then against the case. Then with tissue
paper between it and the case, with screws in securing the PSU.

It's possible that there's something knocking the fan inside the PSU.
You could open the PSU and move any cable away from the fan. It could
be nothing to do with the PSU, it could be that a cable is wacking a
case fan.
Regarding opening the PSU
2 issues to take into account so as not to hurt yourself
* It must be unplugged. Then you won't get electricuted seriously. So
that big fear can blow away.

* That risk above was the big risk. The only risk now is not too bad.
It's the charge in the big capacitors, and you touching a big
capacitor. They , according to googling, will hurt your finger if you
touch them and give you a shock, but probably not much more. You might
want to wait for them to discharge. A day maybe to be safe, i'm not an
electrician. But if you just open it to check a cable - the fan cable
presumably, then you wouldn't be touching them. I think they're covered
by a metal thing anyway like a homeless shelter for capacitors.

And if you're really worried, use your right hand. so electricity
travels down your right side, missing your heart which is on the left
side.