"Neal McEwen" <nmcewen.TakeThisOut@sbcglobal.net> wrote in message
news:P_dhd.9092$bP2.7223@newssvr12.news.prodigy.com...
>I have been trying to fix my son's PC. It is like the monitor does not see
>the computer. When you turn on a computer, it normally goes thru the BIOS
>sequence and shows you what it is doing on the monitor. This PC does not
>even do that.
> The first thing I tried was a new video card -- no luck.
> Then I tried a new motherboard -- no luck.
> The BIOS is on the motherboard, so if the mother board and video card are
> new, what is left?
> I measured all the voltages on the ATX connector from the power supply
> while plugged into the motherboard. They all measure about 30% high on a
> DVM. Is this indicative?
> We unplugged all the ribbon cables, thinking something else was dragging
> down the MB -- no luck.
> I don't think it could be the CPU, because even without a CPU or with a
> bum CPU should'nt it still go thru the BIOS sequence?
> I am open for suggestions. Can anyone give me some fresh ideas?
> Thanks for any help!
>
Do you know that your DVM is OK? To me, your post points to several
symptoms. 30% is way too high for voltage readings. BUT, if your power
supply was bad, it is somewhat unlikely that it would be bad in a way that
your DC voltages would all be about 30% too high. That's why I'm wondering
about the accuracy of your DVM. If your output voltages really ARE 30% too
high, then your CPU is not reading "good" voltage, and thus it will not run
POST. So the simple fix would be to replace the power supply, and hope that
those sky-high voltages did not damage anything else.
For future reference, your computer does (roughly) the following when you
turn it on.
- First, the CPU is looking for a good power signal. Thus, your power
supply has to be OK.
- When CPU sees power good, it starts running POST program stored in BIOS.
(thus your power supply and CPU need to be OK)
- During POST, the video card might eventually be initialized, if the
hardware passes certain very basic checks first.
- If the video card can be initialized, then you will get video on your
monitor, showing RAM being tested and other components being initialized.
- Final step is for the CPU to look for an OS to boot, according to the
boot sequence that is stored in CMOS.
Of those five steps, you have a system that is stuck somewhere in step one
or two. I suspect a bad power supply. But even if I'm right on that, a bad
power supply can lead to other problems. A bad motherboard or bad CPU could
stop the process in step one or two, also. As you've already tried a new
motherboard, you are probably looking at a bad power supply or bad CPU, with
power supply as most likely suspect. -Dave<!-- ~MESSAGE_AFTER~ -->
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