Bikini said:
Hello Everyone...
I have a gateway tower. The computer was running but when I restart it, it
won't boot. I played with the power and the front switch a few times and I
was able to get it to boot finally, but now, it won't boot at all.
It never even boots to the BIOS. I unplugged everything except the Monitor
and keyboard it still won't boot.
It's not beeping. The fan comes on, and there is a LED that blinks a few
times but then nothing else happens. The monitor says NO SIGNAL.
Does anyone have any ideas what can keep it from booting/rebooting. In the
past, I had to unplug it and leave it alone for 5 or 10 minutes before it
would boot up, but as I said, not it won't boot at all.
And one more symptom... When you plug it in, it turns on by itself, without
having to press the on button in the front of the computer.
I'm looking for ideas on where to begin to troubleshoot this issue.. All
ideas would be appreciated.
Thanks in advance...
"And one more symptom... When you plug it in, it turns on by itself"
That is actually an important symptom.
Computers with ATX power supplies have "soft power off". The supply
is split in two pieces. +5VSB runs all the time. The other rails are
switched on, when you push the front button on the computer.
The front button is wired to the Southbridge and SuperI/O chips. Those
chips not only "condition" the momentary contact signal from the front
switch (convert "pulse" to constant level), they also incorporate any other
"wake" events, such as Wake On LAN.
So, now, consider the Southbridge. It is a chip with multiple power
rails. It has the interface to your disk drive. But it also may be
looking at that power switch and have power control related logic.
What I've noticed here, is if the Southbridge chip is "stressed",
it immediately turns on the soft power signals. It means something
is so out of whack, the logic no longer works properly. I've
observed this on my first computer, with a 440BX chipset.
What happened to me, is the IDE ribbon cable was half seated in the
motherboard connector. It got pulled loose while I was working in
the computer. The power came on immediately, as soon as I turned on
the rear power, which scared the crap out of me. After switching
off at the back, and inspecting the cabling, I discovered my mistake.
The machine behaved itself, after the cable was properly seated in
its connector.
What may have happened in your case, is the hard drive or the CDROM
drive may have a failure on their IDE interfaces. Turn off the power
at the back of the computer. Unplug the ribbon cable from the
motherboard end. Turn on the power at the back of the computer.
Does the soft power stay off now ? Do you have to push the power button
to get it to start, as it would normally do ? That might hint that
one of your drives is "stressing" the Southbridge.
When a machine malfunctions, you try to simplify the hardware setup,
removing items which aren't necessary to get the BIOS screen to
appear. Then, see if you can get to the BIOS. Now, turn off the power
at the back, and add components one at a time, and retest. By doing that,
you may uncover what the problem is.
A parallel consideration, is the power supply. On the one hand, the previous
paragraph assumes a 100% healthy power supply. If you heard funny sounds
coming from the supply, the PSU fan stopped spinning, you smell a
"burnt" smell coming from the power supply, these symptoms take priority.
For a lot of brand name supplies, if they die, they have sufficient
protection in the design of the power supply, that they may die quietly,
without damaging anything. But there have been brands in the past,
where a PSU failure damages the motherboard and maybe the hard drive.
The RAM and CPU can be salvaged, but other things get cooked. The
supply notorious for this, was a Bestec 250W. If you owned a Bestec 250W
power supply, and got even a hint of trouble, you'd stop and replace
it first, before something nasty happens. (The brand is printed on
the label of the supply, which you can see with the side off the
computer case.)
So depending on which symptoms have priority, you can either concentrate
your efforts on whether the supply is healthy enough to be switched on
again. A bad supply is like a roulette wheel, and if you flip the power
switch enough times, it will eventually blow. In some cases, the
safety features can even be bypassed, if you insist on torturing it.
(I remember one rocket scientist, who, when the computer would not
start, flicked the power switch on the back 50 times in quick
succession. Um. Don't do that
)
If you see nothing to suggest the power supply is on the way out,
then concentrate on simplifying the setup, and find either a
bad stick of RAM or a bad hard drive or optical drive. If you have
two sticks of RAM, you can test with just one of them present
at a time. Always power off at the back of the computer, before
changing any hardware.
On a retail computer, chances are the IDE devices are jumpered
"cable select", so you won't have to change the jumpers. Remember
the fill rule for the ribbon cable though. When testing one drive
on a ribbon cable, you fill the end connector first. Don't
plug a single drive into the middle connector and leave the end
one empty. The signal quality isn't as good that way. The preferred
configurations are like this. Depending on which of the two
drives you need to unplug for testing, you may need to move
the second drive's connection, to get the preferred configuration.
Mobo -------X-----X
|
Drive
Mobo -------X-----X
| |
Drive Drive
HTH,
Paul
