--- In Jim Jackson <> wrote:
>
>
> On Fri, 14 May 2010, j.chitte wrote:
> > --- In Jim Jackson <jj@> wrote:
> >>
> >> It now boots, but after about 4 or 5 secs it starts constantly rebooting,
> >> output below, along with board LEDs going fron steady green to red then
> >> green, then red then green etc. The reset button has no effect.
> >>
> >> At first I thought it was the power supply developed a problem, so I've
> >> tested with another PSU - same thing. I've disconnected everything
> >> and still same problem.
> >>
> >> Anybody any suggestions at all as to what I might check for? If I'm quick I
> >> can get maybe a couple of redboot commands executed, if anything will give
> >> any diagnostic info.
>
> ...snipped...
> >>
> >> RedBoot>
> >>
> >>>> TS-BOOTROM, Rev 1.02 - built 16:55:24, Sep 14 2004
> >>>> Copyright (C) 2004, Technologic Systems
> >>>> TS-7200: Rev A PLD detected, options ( MAX197-ADC )
> >>
> >>
> >>
> >>>> TS-BOOTROM, Rev 1.02 - built 16:55:24, Sep 14 2004
> >>>> Copyright (C) 2004, Technologic Systems
> >>>> TS-7200: Rev A PLD detected, options ( MAX197-ADC )
> >>
> >> ....repeated over and over
> >>
> > If it is rebooting whilst being held static at the reboot prompt, it must
> > be hardware. It definitely sounds like power brown-out triggering the
> > reboot.
> >
> > Can you monitor the output of the onboard regulator?
>
> Good point. I'll check.
>
> It's a bit wierd. After a quick power cycle it starts the constant reboot
> cycle after about 3 to 4 secs. If it is powered down for a while and then
> powered up. the reboot cycle starts after about 5 to 7 secs. It could be
> something heating up and failing.
>
> The 3.3v and 1.8v regulators are linear on the 7200, so will be
> dissipating heat.
>
> cheers
> Jim
>
I get the impression there is a high resistance in the current path somewhere,
a dry joint maybe. This could be the result of corrosion creeping into a
connection that has a defect.
I was running a 7250 from a power supply that was not able to supply the
current without the voltage dropping and saw similar reboot cycles. The 5V
input only has to drop to about 4.8 or 4.75 to trigger a reboot. There is a
large power demand a few seconds after initial power on that would match what
you are seeing.
I'd guess that the processor is held in a disabled state for a few seconds to
allow power rails to stabilise. That is very likely capacitive RC delay that
would vary with a longer power off period.
I'm sure a bit of poking with a DVM will show you where the problem is.
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