Re: PC doesn't start

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Now I am confused. You changed (swapped) the power supply.
Everything works. Why then would a power switch or connections be
suspect (as defective)? Those voltage readings, if taken before
changing anything, would have identified a power switch, connections,
power supply, or power supply controller (including APCI) as either
good or bad. All we can do now is confirm what is working. Those
voltage measurements say the power switch, power supply controller,
connections, power supply, and APCI are working OK; are not causing
problems.

However, well, first some background. The power supply controller
has inputs from the purple wire and from power switch. To power on
supply, that power supply controller drops the green wire voltage to
near zero. This happens when power switch is pressed.

How to see power switch working: Connect both leads of the meter to
both power switch wires where those wires connect to motherboard.
When switch is not pressed, then voltage must be well above 2.4
volts. When switch is pressed, then that voltage drops to well below
0.8 volts. If those voltages are OK, then switch (and associated
circuit on motherboard) is working just fine. But we know the switch
was working because green wire voltage dropped to near zero when
switch was pressed.

Meanwhile is a 250 watt supply too small? Without first taking
measurements, one could not know. Even worse are how clone power
supplies (selling at a cheaper price) are rated (speced). That 500
watt supply may actually only be 350 watts based in how some clone
manufacturers 'play' (fudge, manipulate, spin) numbers. A true 250
watt supply would be more than enough for most machines.

Again, with that 250 watt supply installed AND by measuring voltages
on an orange, red, and yellow wire while numerous peripherals are
accessed, then we might learn why your system periodically would not
start.

Complex graphics? Play a DVD movie or a video from U Tube. That
would be complex graphics - cause graphics controller to consume more
power. Most power is consumed by CPU, video controller and DVD when
burning a ROM disk. Doing these things are a best test of a power
supply - the best time to measure voltages on an orange, red, and
yellow wires.

Currently your voltage numbers say no problems exist on power switch
or connections. But then you may have 'fixed' them by changing
things. For example, connectors are self cleaning. Once disconnected
and reconnected, then the connection is cleaned. Well if that
connection was the problem, then it was fixed before we identified
it. IOW we still don't know if anything has been 'fixed' (repaired).

For future reference - and this applies to diagnosing any problems -
first collect facts before replacing or fixing anything.

Your English is perfect. I would have never guessed you are
Italian. Meanwhile, my gut feeling (speculation) is that you have
solved the problem. We just don't know why. Sprinkle it with some
holy water before closing the computer. Can't hurt.

On Feb 12, 3:27 pm, "Andrea"
<andrea.delzoppo(removethis)@fastwebnet.it> wrote:
Hi, Tom.
I checked again the orange voltage with CD/Rom running and WMP I do not use
any complex video graphic.
The PSu was changed because of the fan failure on the original one that was
suppused to give only 250 watts. The problem was actually there with the old
PSU.
My suspects are against the front switch or its connections to the MoBo.
Could you help with smart advices to check it properly?
Thanks again Tom; I hope I'm not abusing of your kindness,
Andrea
P.S. Sorry for my poor Eng. I'm writing from Italy


.

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