[iyonix-support] Re: Uncommanded shut-down
- From: Steve Fryatt <lists@xxxxxxxxxxxxxxxxxx>
- To: iyonix-support@xxxxxxxxxxxxx
- Date: Sun, 24 Jul 2011 12:38:49 +0100
On 24 Jul, John wrote in message
<51f7c510d9mail@xxxxxxxxxxxxxxxxxxxxxx>:
> It seems to keep coming back to the PSU: why, if power is on, does pushing
> the power button on the front not work?
The soft-power switch is controlled by the motherboard, not the PSU, so
without checking what's happening on the PSON and PGOOD lines between the
PSU and the motherboard you can't tell much from it at all.
> In fact, this morning I had to cycle the rear switch twice before it would
> come alive. Doesn't that suggest something to do with the PSU?
Again, no. You could just have a problem with something in the soft-power
circuits on the mobo that needs to be reset by cycling the Aux 5V rail
(which only happens when the switch on the back of the PSU is turned off and
left off long enough for the bulk cap to discharge). I've never found the
Iyo to handle 'warm-starts' well at all: if I have to reset, I usually find
it more reliable to cycle the mains at the wall socket as well (as it's more
accessible than the PSU's switch).
Does anyone know if the Iyo mobo uses the PGOOD signal from the PSU? If it
does, then one possibility is that the caps in the PSU are on their way out
and the PSU's inbuilt quality detection is seeing faults and dropping PGOOD.
If the Iyo meets the ATX spec, then this should trigger a panic shutdown.
You would probably need access to a storage oscilloscope to check this,
though.
You could swap the PSU out, but there's a pretty good chance that your
motherboard won't play nicely with another PSU anyway -- unless you get a
"compatible" one from a RISC OS dealer. This rules out swapping it with one
from another computer as a test[1]. So much for the Iyo being ATX
compatible.
1. Although if it is PGOOD, then the other computer should show the same
problem when using the Iyo's PSU.
--
Steve Fryatt - Leeds, England
http://www.stevefryatt.org.uk/
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