I started having "brown out" problems a few months ago. Power LED
flashing & screen flashing between min and max brightness. Twisted the
power plug and eventually the flashing stopped. The situation
deteriorated until the battery would loose charge (charge LED not on)
and the computer would shut down. I thought that it might be the battery
or power adaptor.

I opened the computer reaching the motherboard (not so difficult the
second time around) and resoldered the DC socket to no avail. Openloop
adaptor voltage was 19V (correct), however DC jack only showed 1V when
the power was connected.

Then I noticed the two side spring pins inside the power plug (unusual
for such a connector) that are designed to connect with the motherboard
DC jack central pin. They had lost spring tension and no longer
protruded into the central space of the plug. I used a large pin tool
(large pin with handle, like a scribe, recommend a large needle
otherwise) to wedge the side pins back out again, however only slightly.
Problem solved.

However, the split metal cylinder inside the plug is at a different
voltage to the pins (ground ? a sensing circuit ?), there is very little
space between the side pins and this cylinder, and an accidental short
circuit between one of the side pins and this cylinder with the
adjusting tool, while power is on, will cause a flash and an arc, so
make sure that the power is off for at least 30sec before making the
repair.

Also, only adjust the side pins slightly and evenly without twist. If
they protrude too far into the central space unevenly then can briefly
make contact with the internal cylinder while the plug is being
connected and you will hear an arc. The arc does not appear to have
affected the power supply.

These should not have failed within three years and few
connection/disconnection cycles. The side pins may need to be adjusted
again within a year or so.

If the problem turns out to be the motherboard DC jack, these are
easily available on Ebay, try "ZD7000 jack" or "ZD7000 connector". The
DC power plug is also available here. I would not recommend a regular DC
power plug replacement unless the function of the internal split
cylinder is understood and found to be unnecessary.

Other advice for this overheating computer is do blast the air vents
twice+/year to clear the heatsink dust (reverse vacuum cleaner or can or
compressed air), and raise the back of the computer at least 1" (I am
currently using a telephone directory just under the rear rubber feet)
to greatly improve air flow. You will hear the fans run much more slowly
and more quietly with these two measures. It also stopped my computer
from regularly shutting down.

I am also going to go one step further and get a laptop support that
will raise the screen about 6", placing it at eye level, and further
improve air flow. Overheating may also be the source of some of the
other problems mentioned for this computer.

DH