Re: siren when PC power is on

On 7 June 2016 at 20:09, Aleksandar Kuktin <[email protected]> wrote:

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> >On Tue, 7 Jun 2016 19:36:43 +0100
> >Ken Moffat <[email protected]> wrote:
> >
> > On 7 June 2016 at 18:18, Aleksandar Kuktin <[email protected]> wrote:
>
> > I'm not familiar with the sound a dead psu makes.  I had one a few
> > years ago, all I remember is the burnt smell. The sound is
> > high-pitched, probably in the high hundreds of Hz, or maybe 1 KHz.
> > But before I sent this reply I googled for the sound of a dead PSU -
> > one forum post where a new PSU solved the problem does seem to match
> > what I'm hearing.
>
> I would have been "happier" with, say, 50 kHz because switching power
> supplies (the kind that gets put into PSUs) usually operate internally
> at about that frequency.
>

I don't think I would hear even 15 KHz.
[...]

>
> >> I'm not clear about the actual symptoms you are having. I'll post my
> >> understanding, you correct my mistakes.
>
> > For the test machine: as soon as I turn the switch on the PSU to 'on'
> > the sound starts. If I then press the power switch on the case the
> > motherboard and CPU fans both start, but I seem to not have any video
> > output (that might be luser error - the KVM switch is dieing, only one
> > position works reliably, maybe I misconnected after failing to boot
> > the test machine to try to do a clean shutdown andlater swapping it
> > back).
>
> Does it beep? A properly operating motherboard will beep twice. In this
> case, the most important beep is the first one. That's the motherboard
> firmware saying "I'm alive". Fans are simple devices and will operate
> even if the PSU outputs "wrong electricity", say a train of 100Hz
> pulses instead of a steady voltage.
>
> No beep. But I don't think it has any speaker connected.


> > [snip]
> >
> > Getting space to open them is a pain, but yes I have other machines
> > (using one of them at the moment).
>
> You'll probably need to open the machines.
>
> The traditional way of doing this is to have a known good computer and
> then swap in parts from a broken computer, waiting to see when it will
> fail. In theory, I'd first concentrate on the disks and make sure they
> are alive. If the disks failed (got fried), then you will at least
> discover that early. But in practice, it's probably good enough to
> replace the PSU with a known good one and see if the machine boots.
> Make sure the KVM magic is working well. :) If it does not boot, I'd do
> the whole transplant-bit-by-bit ritual. Beware hasty conclusions.
>
>
Yes, I've done this in the past. That test machine is the one I would
have used to test a new or doubtful disk (light case, easy to access in
its current location) - using one of the others will take a bit of time.


> > The server would have been running and I won't be surprised by a
> > failed PSU. But the test machine was using minimal power (nominally
> > powered off, probably 5 Watts maximum) and it is perhaps a year old,
> > maybe two, but unlikey to be more than that.
>
> Hmm.. bizarre. Yet, everything is possible. Note that the fact the PSU
> was switched off may not be of any significance. There's no way to know
> without knowing more about its internals.
>

Thanks.  I'll see about looking at the SSD from the test machine, then
probably get a PSU or two. For the moment I'm not touching the server,
I seem to have developed an ability to break things recently.

ĸen

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