Okay so last night the karaoke DJ's laptop wouldn't turn on. I held the power button in, pressed the power button, tapped the power button...nothing.

Apparently he had put it on sleep before he left his house and as soon as he got here it wouldn't turn on at all and there was basically no power.

Well I noticed two USB devices connected at the back of the laptop. As soon as I unplugged these the laptop turned on straight away.

Now I know how I fixed it but I would just like someone to explain the tech side of it because I am not sure.

I THINK when the laptop went into sleep it made a record of all the connected hardware. And then because when he tried turning it back on the connected hardware differed from what it had registered, it wouldn't power on.

Is that right? It just seems a little...over protective.

Thanks

Hey Amtech.

Ok not going to explain Technicaly.

Marked as "Open" for others to input.

You can configure the hybernate and sleep mode via BIOS and power settings within windows.

If it is Vista it has lot more options that can be set on how the computer sleeps and wakes unlike XP.

Anyway Open for others to input.

I suspect, Amtech, the USB devices were holding the control signal voltage below tolerance. Unpowered USB devices get their power off the 5volt pin of the BUS. The control signal draws from the 5volts. Unless things have changed much, the USB port is still live even when you put the laptop to sleep.

LC

USB devices can be configured to shut/power down and/or put the system to sleep.

Once unplugged, that restraint on the system goes away. Awake!

The configuration of what that system does with external devices needs to be looked at.

It should not be in control of system sleep/wake demands.

That invites bigger problems than this one was.

You are quiet right Sir Trews. My comments derive from having to show customers that unpowered USB devices can keep a laptop or desktop PC from booting or coming out of hibernation. It was strickly an assumption based on observation.

LC

Okay just explain it a bit more please .

Does the laptop allocate a certain level of voltage for [Sleep Mode] And did the USB devices interrupt its voltage supply and cause it to malfunction / stop working?

Sorry, I'm a nooblet!

Me thinks you are far from a nooblet friend Amtech. I believe the problem is caused because unpowered USB devices draw down the 5volt circuit just below a certian tolerance. Now, If I remember correctly, The control signal is only measured in millivolts but certain conditions must be met on the 5volt circuit for startup or wakeup in this case. One of those conditions is a minimum voltage on the 5volt line. I can see this happen when you have a battery that is weak or below a certain level or more than one unpowered USB device on the port. I've seen problems like this when someone plugs an unpowered hub into the laptop then try to carry one or two devices. Please remember, My comments are derived from observations and never truely tested in real time. I would surely welcome being proven wrong. There is no shame in that and much gained...

Oh and to answer your question. No. The 5volts "In a perfect world." should be 5volts plus or minus. But being to far on the minus side is where we get into trouble.


LC