[kwlug-disc] Strange poweron problem

[Charles M]

To be clear Jeff, you're saying your USB hub does have a small power
transformer that plugs into the wall and gives the USB hub power (i.e.
It doesn't try to draw all the power from the computer)?

If not, this could be the issue.

We used to have problems in CR with our USB KVM (Keyboard Video Mouse)
Switches, they would draw just enough power away from the USB ports
that when we plugged in a USB flash drive it would always appear to
fail. As soon as we removed the KVM switch the same USB drives would
appear. For us the problem started going away as we got newer
computers in, but it still happens the odd time with older machines.
This seems to be why some KVM switches have the option of external
power (but almost never come with the adapter).

The computer is probably newish, you might also try running a
multimeter on that 3V CMOS battery. The odd time we've seen computers
where the CMOS battery was so low it caused the system not to POST or
to POST erratically.


It could of course be the USB hub.

On Mon, Jul 25, 2016 at 11:55 AM, CrankyOldBugger
<crankyoldbugger at gmail.com> wrote:
> It is a powered (ie. it has a small transformer) USB port so I would imagine
> that it would handle the keyboard's requirements.
>
> Googling this issue doesn't do much, but I did find one site where they
> suspected that the hub is bad, and you seem to suspect the same thing, so I
> will test that theory tonight.
>
>
>
> On Mon, 25 Jul 2016 at 11:39 L.D. Paniak <ldpaniak at fourpisolutions.com>
> wrote:
>>
>> Sounds like a weak power supply/heavy draw on the USB port.
>> Keyboards can sometimes be surprising power sinks.
>> It would not surprise me if you took the USB3 hub out your
>> problem would go away.
>>
>>
>>
>> On 07/25/2016 10:59 AM, CrankyOldBugger wrote:
>>
>> I have an older machine running Ubuntu 16.04.  I'm having a strange
>> problem with booting it.
>>
>> The system is a Intel® Quad-Core Processor J1900 + Micro ATX Motherboard
>> (one of those motherboard with CPU bundles from Canada Computers).
>>
>> If I try to power on from cold, the power switch does nothing.  No lights,
>> no noise, nada.  But if I unplug the USB cable in the back, the power switch
>> lights up and away we go.  The USB cable in question is the only USB device
>> attached, and it goes to a USB 3 hub on the desk which currently has my
>> keyboard and mouse plugged in.  (It doesn't matter if I unplug the cable
>> from the back of the PC or the hub itself, the results are the same.)
>>
>> So my question is why would the presence of a USB device stop the system
>> from powering up, and even more so, why would unplugging the cable cause the
>> system to suddenly power on?
>>
>> Sometimes after I do manage to get power on and we go through the POST
>> Ubuntu will get stuck, but a repeat of power off, power on, unplug USB cable
>> seems to clear that up.  I don't think this is related to the power issue
>> but I can't rule that out yet.
>>
>> While I can live with the frustration of unplugging cables when I'm
>> sitting there, it makes rebooting from remote login a pain.  I have maybe a
>> one in three chance of seeing the system come back from remove reboot.
>>
>> Any ideas?
>>
>>
>>
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>
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-- 
Charles McColm, Author: Instant XBMC,
Columnist: Full Circle Magazine,
Project Manager: The Working Centre Computer Recycling Project
Web: http://www.theworkingcentre.org/cr/
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