HP ZX5000 AC Power Issues

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A story continued from the "AC Adapter Lifespan?" thread (basically
that was, "is an AC Adapter a consumable?")...

As it turns out, the AC Adapter is not the cause of my HP ZX5000
Pavilion spontaneously switching from AC power to battery (the
replacement exhibits the same behaviour).  Other possible causes of the
switchover that I have ruled out are the battery itself (laptop
spontaneously turned off when the battery was removed) or a bad
connection at the power jack (laptop switches to battery while laptop
is sitting on desk -- does not switch back to AC except by removing and
replugging the jack -- jiggling wire or plug causes no switchover in
either direction).

It has been suggested by HP technical support that it could be a
problem with any one of the numerous APCI drivers installed for
handling power management.  I find this somewhat hard to believe, but
if somebody tells me I'm wrong, I'll go down that road.  The suggestion
was to remove all APCI drivers, reboot, and let Windows XP Pro
reinstall all of them.  I'm just not seeing the proper risk/reward to
try that without a second opinion.

I am now assuming something on the motherboard, or attached to it, is
giving up the ghost which I'm actually OK with since I have the
extended warranty, but before I let anyone tear my laptop completely
apart for no good reason, the questions:

1) Should I really give the APCI driver reinstallation a shot?

2) Am I missing anything else?

3) If a teardown is required, is there any reason to send the hard
drive with the laptop for HP to repair this?  While I do have the hard
drive backed up, I'd really rather not give them the opportunity to
"cleanse" my harddrive if there is no need for it...

4) For my furthering education, does anyone know the exact mechanism(s)
laptops use to detect the presence of AC power?  I assume it's simply a
conversion of the 18VDC to a digital input pin monitored by the
operating system.  I'm also guessing there must be some hysteresis
built in since it never spontaneously switches back to AC.  Pointers to
documentation gladly accepted in lieu of long explanations here...


Re: HP ZX5000 AC Power Issues

Steve wrote:

Quoted text here. Click to load it

Most portable computers have a separate microcontroller (sometimes, but
not usually, part of the KBC) handling power control issues. It's often
referred to as the "system supervisor"; it handles the charge LEDs or
LCD icons, battery testing, low-power shutdown, etc.

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