[iyonix-support] Re: Some Guidance Required Please
- From: Steve Fryatt <lists@xxxxxxxxxxxxxxxxxx>
- To: iyonix-support@xxxxxxxxxxxxx
- Date: Sat, 30 Apr 2011 12:21:27 +0100
On 30 Apr, Julie wrote in message
<51cbf543f2julie@xxxxxxxxxxxxxxxxxxxxxxx>:
> On 30 Apr, John Ballance <jwb@xxxxxxxxxx> wrote:
>
> > Seriously though, the interrelationship of all the different supply
> > voltages within the iyo, derived from this 5v supply, was always a
> > juggling act. Additionally most of the power supplies we were able to
> > source at the time were reluctant to provide a stable output voltage at
> > the relatively small load (for the time) that our friend consumed.
>
> > I forget what proportion of supply variants we had to reject as
> > unpredictable in the development phases of the iyo.
What worries me is that when my original PSU failed, I found that this
Iyonix was unstable on a new PSU that -- as far as I could tell -- was
operating within the ATX spec when fitted in the machine (and I've got a
fair idea of how to check that, as explained below). This means that it
doesn't seem to be possible to just go and buy a new PSU, safe in the
knowledge that it will work.
Are there any figures available for the actual load and regulation
requirements of the Iyonix motherboard? I'm guessing that regulation must
be "to ATX spec" as that's what the mobo is supposed to be? If we knew what
loads it places on the various rails, then identifying replacement PSUs
might be a bit less trial-and-error.
> My professional curiosity now being thoroughly aroused, I shall have to
> get hold of the technical references for the Iyo and have a look!
What you need is a copy of the Power Supply part of the ATX Specification:
http://www.formfactors.org/developer/specs/ATX12V_PSDG_2_2_public_br2.pdf
If you read that document, you'll understand why I keep pointing out that
the "5.06V test" is (as John reiterates above) at best a *guide* for the
*specific* *model* of PSU originally supplied with the Iyonix. Fully
checking that the outputs of an ATX PSU meet spec by hand can take several
days, and even on automated kit able to take several measurements a second
it takes several hours and produces vast amounts of data to sanity check. Of
course there are shortcuts which will be used for post-production testing,
but you need to know about the detailed performance of the specific model of
PSU that you're looking at to be able to use them.
You also need the correct kit, and it's not the kind of thing that even most
engineers would have lying around at home. You're looking for fast edges
and narrow spikes on the output voltages, meaning that a high bandwidth,
correctly calibrated 'scope and probes is essential. A DVM isn't going to
be any use.
> Things are obviously a lot more complicated these days.
They have been for a long time: I was helping to design ATX PSUs to an
earlier revision of the above spec in the late '90s, and AFAIK the
requirements weren't cutting-edge even then.
--
Steve Fryatt - Leeds, England
http://www.stevefryatt.org.uk/
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