[iyonix-support] Re: PSU
- From: Steve Fryatt <lists@xxxxxxxxxxxxxxxxxx>
- To: iyonix-support@xxxxxxxxxxxxx
- Date: Tue, 21 Sep 2010 22:25:47 +0100
On 21 Sep, charles wrote in message
<515a31c3e8charles@xxxxxxxxxxxxxxxxxxxxxxx>:
> In article <gemini.l93et10078rhk01ls.alan@xxxxxxxxxxxxxxx>, Alan Wrigley
> <alan@xxxxxxxxxxxxxxx> wrote:
> > Steve Fryatt <lists@xxxxxxxxxxxxxxxxxx> wrote:
>
> > > If you have a spare PSU, then try fitting it and see if it works. If
> > > it does, then box it all up and cross your fingers... 250W should be
> > > plenty.
>
> > Well it seems to have been happy for several days now with 250W. So I
> > think you're right.
>
> The real problem is whether the power supply regulates properly on such a
> low load.
Not really. As I think I reported at the time, I compared two PSUs in the
same Iyonix, and found that one (the smaller, which I think is 350W and was
of HEC brand) was fine while the other (the larger, which off the top of my
head was a well-branded 400W that looked "well made") suffered the
well-documented regular disc interface lock-ups. If presented with the two
PSUs side by side, and no other information, I would have selected the
branded 400W every time as being more likely to be better.
Both PSUs, when measured in the machine, under similar loadings and similar
system activity, fully complied with the ATX specification in terms of max
and min voltages along with transients and step sizes. The 400W has since
been running in a standard ATX-based PC.
My impression is that the Iyonix needs something from its PSU over and above
that which can be reasonably expected from a unit complying with the ATX
spec. Unfortunately, trying to pin that "something" down seems to be a
problem -- if we could, it would make fault diagnosis and PSU replacement
much easier.
> This is, almost certainly, a situation where bigger is not necessarily
> better.
If asked to guess, I'd suggest that it has more to do with the
post-regulation stages applied to the main PSU outputs inside the PSU, and
the way that the 3V3 and 5V outputs are regulated relative to each other.
--
Steve Fryatt - Leeds, England
http://www.stevefryatt.org.uk/
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