On Wed, 3 Feb 2016 22:14:12 -0800, "David Farber"
wrote:
I'm servicing a Gateway GM5260. It uses an Intel DP965LV motherboard and it
has Windows XP installed. It also has this habit of freezing randomly. Then
you are forced to hold in the power button to shut it off. Here is the
interesting part. When you power it back on after it freezes, it will ALWAYS
shut down about 1 second after the power button is pressed. If you restart
it second time, usually it will power up fine. Occasionally, it will take a
third try to keep the power on. If the computer goes through a normal shut
down, the power up process always works the first time. I've swapped the
RAM, video card, and power supply, and it made no difference. The only
hardware issue I can find is that in the system bios, there is a value in
the hardware monitor called, +1.5V and it hovers around 1.298V. I have
inspected the caps and they don't look or test bad. The CPU and motherboard
temps are normal. Has anyone experienced this type of problem before?
Thanks for your replies.
Your description sounds exactly like the usual bulging capacitor
problem on the motherboard or in the power supply. You said that you
checked (tested?) the motherboard caps, but did you check the power
supply caps? The hardware monitor is more commonly called the "power
good" line on an ATX power supply. It's suppose to be near +5V so
your +1.5v indicates that the power supply is not happy.
https://en.wikipedia.org/wiki/Power_good_signal
Incidentally, what's happening is that when cold, the ESR (equivalent
series resistance) of the electrolytic capacitors is rather high,
resulting in lots of ripple, lousy regulation, bad breath, circuit
malfunction, and other undesirable things. However, as the capacitor
gets warmed up by the ripple current or nearby hot components, the ESR
goes down allowing the sick capacitor to act like a good capacitor.
The computah will probably work reasonably well, as long as it stays
warm, but will revert to simulating a stubborn mule when it cools
down.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558