Drives and motherboard are powered, but computer won't turn on

[adambubolz]

When you plug in the power cord, the floppy and cd rom drive lights
flash and the processor fan turns on. These keep flashing until you
unplug the power. Pressing the power button does nothing, the computer
does not turn on. I have tried 2 different power supplies and both
produce the same results.

What could be the problem here? I thought it was the power supply but
it does not appear to be.

 

[Ken Maltby]

When you plug in the power cord, the floppy and cd rom drive lights
flash and the processor fan turns on. These keep flashing until you
unplug the power. Pressing the power button does nothing, the computer
does not turn on. I have tried 2 different power supplies and both
produce the same results.

What could be the problem here? I thought it was the power supply but
it does not appear to be.

The CPU fan and the drive lights shouldn't come on until
the "Power" button is pressed. Your PS/2 keyboard and
mouse could light and the little green light on the MB
should light before or without pressing the power button.

The USB controller could also be involved. Try not
having anything USB plugged in, at start up.

Luck;
Ken

 

[Rod Speed]

When you plug in the power cord, the floppy and cd
rom drive lights flash and the processor fan turns on.

That shouldnt happen unless you have reconfigured
the bios setting to start on power available.

These keep flashing until you unplug the power.

What happens to the fans when that is happening ?

Pressing the power button does nothing, the computer does not turn on.
I have tried 2 different power supplies and both produce the same results.

What could be the problem here?

Looks like the motherboard is the problem.

There isnt much else that can produce that effect now that you have tried two power supplys.

I thought it was the power supply but it does not appear to be.

Yeah, very unlikely to have two with such an unusual symptom in a row.

It is a standard ATX system presumably ?

 

[Gerard Bok]

When you plug in the power cord, the floppy and cd rom drive lights
flash and the processor fan turns on. These keep flashing until you
unplug the power. Pressing the power button does nothing, the computer
does not turn on. I have tried 2 different power supplies and both
produce the same results.

What could be the problem here? I thought it was the power supply but
it does not appear to be.

Are you 100% you have a suitable PSU ?
I can imagine some scenario like: Dell PSU going down, system
won't run on a standard PSU either

Can you tell us, what happened before you got this problem ?

 

[DaveW]

If the PSU's were indeed working properly and of adequate power output, then
it sounds like the motherboard is dead.

 

[w_tom]

Notice the many answers of "it could be this or it could be that".
It is called shotgunning. You want a solution. That means your
replies will only be as good as the information provided. Two minutes
with a 3.5 digit multimeter provides that answer. Multimeters are now
a consumer tool as essential as a screwdriver and so ubiquitous as to
be sold even in K-mart.

First measure DC voltage on purple wire from power supply to
motherboard. Push the red probe into the back of a nylon connector to
make contact. Black probe can connect to chassis. That voltage must
exceed 4.87 when computer is off.

Next measure voltage on green wire. That voltage must be well above
2 volts and then drop immediately to well below 0.8 volts when power
switch is pressed.

Next measure gray wire. Voltage should rise to well above 2.4 volts
within seconds of power switch being pressed.

And finally, what are the numbers on any one of orange, red, and
yellow wires. What happens to each when power switch is pressed? And
each voltage must than maintain above 3.23, 4.87, and 11.7 volts.

Those numbers tell us where the problem resided. Furthermore, post
those numbers to learn additional information or even better identify
the problem. In but two minutes, we don't say "it could be this or
that". In but two minutes we are point at a specific suspect. No 'it
appears to be'. It is or it is not if using the meter.

 

[Rod Speed]

Notice the many answers of "it could be this or it could be that".
It is called shotgunning. You want a solution. That means your
replies will only be as good as the information provided. Two
minutes with a 3.5 digit multimeter provides that answer.

Pigs arse it does, most obviously with excessive ripple on the power supply.

<reams of your mindless silly shit that proves in spades that you dont
even understand how a multimeter works flushed where it belongs>