NewToFPGA said:
I dont find the K45 anywhere near the CMOS battery. I all see are
starting with R, C, ST, ....
I had to change the power supply before a week ago. Do you think it
has happened again?
Well, there is a trick you can use, to make a power supply run.
Connect PS_ON# to COM. Wiring diagrams and colors are documented here.
24 pin
http://www.formfactors.org/developer/specs/ATX12V_PSDG_2_2_public_br2.pdf
20 pin
http://www.formfactors.org/developer/specs/atx/ATX12V_1_3dg.pdf
The PS_ON# signal is open collector. Or is supposed to be. The power
supply input signal, should have a pullup on it. The motherboard pulls
that signal to ground, to make the PSU fan spin, and cause all main outputs
to appear. You can connect PS_ON# to COM, and make the PSU run.
The dangers with such a technique.
1) The PSU only runs, as long as there is a wire from PS_ON# to COM.
So if there isn't a good connection, the computer could stop or reset.
2) Computers have overheat protection. If the computer overheats, it has
the ability to turn off the computer. But if you use a jumper to keep
PS_ON# going, then the computer has "lost control". It is no longer
in charge of "switch on" and "turn off". So you lose a protection feature.
If the CPU overheats, while you have left the room, then the CPU could fry.
So the technique will work, but is not the safest thing to do. By defeating
safety features, you increase the odds of something bad happening. But you
can certainly try this for a temporary test. (Connect PS_ON# to COM,
see the BIOS screen appear, then switch off again by removing the shunt.)
If this was my computer, and it wouldn't go, this is the test case I would try.
1) Remove motherboard from computer case. That avoids accidental shorts to the
bottom of the motherboard, as a cause of the failure.
2) Remove processor and RAM from the motherboard. Pull add-in cards.
You want the motherboard, power supply, power switch to PANEL header.
3) If the motherboard has a green LED to monitor +5VSB, verify the LED lights
up when the power supply is switched on at the back. If there is no LED
(a cheap motherboard), then use a multimeter to verify +5VSB is present.
If not, find out why.
4) Press the front power button. The motherboard logic circuit, powered by +5VSB,
should be asserting (grounding) PS_ON#. The power supply should start, and
the fan should spin. Since both processor and RAM are missing, it cannot
boot. There is no video card or other cards present either. So there is
nothing to see. The whole purpose of this test, is to verify that the
motherboard could turn on the power supply. If the test passes, add
components one at a time, and carry out additional test cases, until a
failure is again observed.
I've built up my last two computer systems completely on a table, without
mounting them in a computer case. That allowed me to add a component at a
time, and verify it worked. I even installed the OS and got the Windows
desktop, while all the stuff was sitting on the table. It is a lot easier
to see what you're doing, with the motherboard out in the open. The only
danger, is there is no way to keep the video card secured in its slot, so
you have to be extra careful to not tug on the cable. If you have small
children in the area, this is not a good test to do.
HTH,
Paul