New PC - No Power?

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Have just built an Athlon 64 X2 Dual Core Machine with an AM2 Motherboard,
SATA Hardrive, 500W PSU etc.
When I turn the power on, the Motherboard Light turns on, but when the power
button is pressed, nothing happens.. ie fans don't spin, speaker doesn't
beep... nothing.

Have checked the Power Switch cable is connected to the motherboard ok and
have racked my brains trying to figure out any other reason. Other than a
broken power button on the case, what else might the problem be?



Re: New PC - No Power?

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Try jumping the pins with a flat head screwdriver.  Once your sure you have
located the correct power switch pins, connect them together with the
screwdriver.   This should start the system.   You only got to jump them for
a second, once started you move the screwdriver away.

If it starts then it's the power button on the case.

Re: New PC - No Power?


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Providing more details such as make &  model (and wattage,
of PSU including 12V current rating) of the parts might

Try clearing CMOS.  Check cards, cables, wires, and
connectors (like the 4 pin 12V connector for CPU, it seems
more commonly overlooked on occasion).

Try stripping system down to bare essentials- nothing
connected (not even keyboard, drives, and case connections
to the switches and LEDs up front) except 1 memory module,
CPU, heatsink/fan, and the least demanding video card you
have (a 10 year old PCI card would be ideal) even if it has
onboard video, though if the onboard video is the problem it
might help to try a PCI Express video card instead.  Try to
get it to POST in this minimal configuration.

Take voltage readings of the PSU rails if you have a

Check your motherboard manufacturer's bios (download)
revision notes to see if any subsequent bios releases seem
to effect your uses/parts.

You can disconnect all the case front panel wiring including
the switches then use a metal object (screwdriver,
paperclip, etc) to short the two power-on pins together.
Consult the manual to be sure you have the right two pins
for power.

If all else fails, it would help to have a 2nd system as
compatible as possible to individually test any suspect
parts in, or to swap parts from to confirm any suspect part
is bad.  "Generally" speaking, motherboards and PSU are the
two most common problem parts.  Motherboards due to
incompatibility, physical (incl. ESD) damage, or PSU due to
insufficient design, overrated output.  Of course
user/assembler mistakes have to be up there as popular
causes as well, but if I were playing odds and none of the
above helps, the PSU is the first part I'd swap out
(especially if it's a generic brand).

Re: New PC - No Power?

500W PSU is Jean Tech but have also tried with Nexus 420W PSU.
Neither work in this machine, but both work on other which leads me to think

Tried clearing CMOS, no avail.

MB should support the 6000+  (ABit AN-M2HD)

RE: Bios - Don't see how I can update if I can't even get to bios screen?

Power button works fine.

Stripped down whole system to just CPU, 1 Mem Stick and 1 Case Fan.
When power button pressed, I then got the tiniest flash of a green LED on
the motherboard but no fan movement.

Guess I'll RMA the motherboard?

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Re: New PC - No Power?

Ravix wrote:
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With regard to your comment about the "LED". There are two motherboard LEDs.
One is next to the main ATX power and is the VCC LED. That should light up
when the board is started by the front power button.

The second LED is +5VSB. It is near the SATA connectors. It should light up
steady, as long as the switch on the back of the computer is in the ON
position. +5VSB is present, for as long as the PSU power switch is on.
+5VSB should not blink - if it blinks or glitches, that tells you that
something on the motherboard is drawing more than the 2 to 3 amps the supply
is rated for on that rail.

If the VCC LED flashes only for an instant, that means a main power rail is
being overloaded. For example, if a cable with rail voltage on it, got pinched
on a grounded piece of metal, the power supply should switch off when the
overload is detected. The reason the VCC LED flashes, is because the power
supply is designed to ignore overcurrent indications, for the first 35 to 50
milliseconds or so. When the ATX power supply is charging the motherboard
bypass capacitors, that takes quite a bit of current, and so the PSU is
told to ignore the large instantaneous load. That is when the LED flashes,
because the power is not being stopped for that short instant. Once the
overload is detected and used by the PSU control, the PSU stops its outputs,
to protect whatever is causing the overload.

Check cable wiring and polarity carefully. For example, there have been
cases where the ATX12V 2x2 connector was on backwards. Check the pinout in
the manual, and make sure the yellow wires on the 2x2, go to the pins marked in
the manual as +12V pins. The two black wires are grounds.

If you owned a multimeter, you could disconnect the power supply, and then
do rail-to-rail checks with the multimeter set on low ohms. If something
reads zero ohms, you'd want to visually inspect and figure out why. (Low
ohms reading are still possible, so it takes a bit of experience to guess
as to what is normal. The ohmmeter test is easier to do, if you have
other identical motherboards to compare to.)

It could be something as simple as a standoff that is touching a power
track on the bottom of the motherboard. Motherboards have grounded rings
on the bottom of the board, and those are meant to be touched by metal
standoffs. If a standoff lines up with something which is not a ground
ring, that could be your problem.


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Re: New PC - No Power?

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This is the one that flashes, it's a very tiny LED next to the Floppy Disk

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This is fine and is on steady .

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OK will do. I

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I don't  :(

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Will try lifting the board out of the case (onto a wooden desk) and try
running with minimal components again..

Thanks  Paul,


Re: New PC - No Power?


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... including 12V current rating...
I don't know or don't remember what a Nexus 420W is like
(maybe SPI/Sparkle/Fortron, though older or newer generation
could determine current capability per rail) but the Jean
Tech isn't very good.  Since the Jean Tech is a wildcard I
would continue attempts with the Nexus.

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It can't be concluded yet, just because a psu works to some
degree in some system doesn't mean a different system has
the same power requirements, particularly current. "IF" the
two systems have fairly equal current per rail, and the one
in question doesn't have a significantly higher capacitive
load, it "might" suggest the PSU isn't the problem.  I'm
being cautious in these statements because it's a JeanTech
PSU which in itself is already sub-optimal even if it were
working as it's *designer* (or bean-counter re-spec)

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The issue isn't necessarily one of how to update when it
isn't posting, it's about identifying the problem.  This
"probably" isn't the problem, but if we reject all things
that probably aren't the problem, lots of problems on
various systems wouldn't ever be solved.

You wouldn't have to see (if we could forsee all problems,
everything would always work right on the first try 100% of
the time?) , rather to just check because only through
reading the notes will you see that what a board is
"suppposed" to do, might have to be patched to do via later
bios revisions.  Unfortunately not all changes to a bios are
documented (or at least the info is not released in brief
notes), but it is one place to look.  I didn't see anything
related but I didn't download the files and open them to see
if there were more detailed notes enclosed.

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Since you'd have to take it out of the case anyway to do
that, set it up on a non-conductive surface (not
ESD-protective packaging, not the bag or foam, etc) again in
the minimal configuration and clear CMOS again while AC
power is disconnected.  

Paul made some good suggestions about checks you could do
with a multimeter.  It does seem most likely to be either
CPU or motherboard but if no other clues turn up (after
trying it outside the case) you will just have to try
replacing one or the other with the hopes that you picked
the right one.  Motherboard might be a more likely suspect
but the Jean Tech PSU probably ought to be avoided until
you're sure it isn't PSU.

Re: New PC - No Power?

To quote the great Homer Simpson....


Solved it....(somewhat embarassingly)

The board is a MicroATX and the 3 pin wire for bottom casefan in the hard
drive area wouldn't reach the board connector due to shortened board. To
remedy this, I had installed a 3 pin "Y" splitter than I had lying around,
as an extension. The "Y" Splitter comes with 2 small plastic "Jumper" style
covers to cover the red and black pins when not in use (so as not to short
out by the none connected end touching the case or any other metal etc).
They are identical to HD / DVD Drive jumpers, but are hollow. What I had
accidentially done, was pick up an actual HD Jumper (with metal internal)
rather than the "Y" splitter's plastic cover and thus managed to connect the
red wire direct to the black wire and form a circuit! (Shakes head). When
stripping down the system to minimal components, I had disconnected the case
fan but not the Y extension.

Feel free to nominate me for the idiot of the week award!

Regardless, Thanks for all the help guys, really appreciate it. In every
mistake there's a lesson to learn....


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