Now you understand why I "bench test" on the kitchen table first,
before putting the system in the computer case.
You don't absolutely need *any* wiring to the front panel at all,
for a bench test. But what I do instead, is keep a push button switch
with two connector pins on the end, which slide over the PWR and Ground
pin pair. That's for turning the system on. I can also slip a screwdriver
tip between those two pins, to bridge them and start the system. That
requires a good deal of care and dexterity, and is only
practical when the motherboard is sitting on the kitchen table.
http://i61.tinypic.com/28bgwf9.gif
On the picture there, you can see that header has a "dangerous pair"
in the SPKR pin area. Don't bridge that +5V pin if you can possibly
manage it, to any adjacent Ground pins. It's another one of those
situations where there may be no protective fuse in the path.
*******
In the past, some Antecs have had wiring errors in USB or Firewire
cables (that's a 2x5 on the motherboard end, leading to a front
panel mounted connector). So I would not hook up the front panel I/O
wiring at all. On a couple Antec cases here (I have at least three
of them), I use the multimeter, set to ohms range, to verify the cable
wiring is correct. It's just easier to *not* use Antec front wiring, than
be bothered to do that. None of my Antec front USB ports are hooked up,
for this reason. I'm too lazy to correct the errors by moving the
pins around in the 2x5 end.
*******
I take it, OCZ had you do the "unconnected supply" test ?
For that one, you bridge PS_ON# to GND on the ATX cable.
Bringing the logic level low on PS_ON# is what makes
the supply fan spin, and the main supply section to function.
On page 37 here, that would be the green PS_ON# wire, to an
adjacent black GND wire. Some people recommend connecting
a dummy load to the supply, in the form of an old (scratch)
hard drive or something that draws a similar small amount
of power.
http://www.formfactors.org/developer/specs/ATX12V_PSDG_2_2_public_br2.pdf
*******
This is a simplified model of the ATX supply. There are two
power generation circuits, and +5VSB is separate from the rest.
AC Input ------+--- +5VSB circuit
|
+--- +3.3/5.0/12V main section
When you switch the supply on at the back, the +5VSB starts to
produce power immediately. The fan will not be spinning at
this point. The +5VSB provides 2 to 3 amps max, and is
used as a supervisory voltage, amongst other uses. The
ATX power supply is convection cooled at this point, when
removing heat from the +5VSB circuit. Due to the modest
capacity of the +5VSB, it doesn't get too warm.
When the ATX power supply main cable has PS_ON# and GND
brought together, that grounds the pullup resistor on
PS_ON#. Normally, with a voltmeter, you'd see 5 volts
level on PS_ON#, and it's when that level is grounded
that the supply runs. The fan begins to spin, and the
main voltages begin to be produced. The motherboard
would be starting to POST at this point. The case
fans would be spinning.
If you attempt to start an ATX supply, and you see
the PSU fan "twitch" about a half inch of rotation,
that means the supply tried to start, but encountered
a serious short circuit (current overload) on the outputs.
To protect against burning any cables, the ATX supply
has latched off. Normally, you'd need to switch off at
the back, wait 30 seconds, switch on again, to make
another attempt to start the system. The reason the
supply "twitches", is the overcurrent is disabled
for the first 35 milliseconds, until the PSU has had
a chance to charge the output capacitors, and that
allows the fans to receive current for 35 milliseconds.
The fan blades can only "twitch" in such a short time
frame. If the "serious short" is present, when the
overcurrent detection is enabled at 35 milliseconds,
the power supply immediately shuts off the main section.
(The reason you wait 30 seconds, is to give any inrush
limiter time to cool off.)
In this diagram, the +5VSB is used to power the control
circuits. The motherboard logic "latches" the momentary
logic low level from the front panel switch, and drives
out a "steady" 0.0V level on PSON#. And that's what is
used to control the ATX supply.
+5VSB (0.0V level +5VSB
| means "run please") |
Pullup \_ Pullup
Resistor \ Resistor
| PS_ON# |
PWR X----+---- Motherboard ---- Open -------------------+- ...
control
/ logic Collector (to of
main
| GND X----+ Driver ATX + PSU
| | supply) |
section
(Front GND GND
Panel
Switch - normally open, momentarily close to operate)
By removing any USB panel header or Firewire panel header wiring
from the front panel to the motherboard, you're removing
a possible place for electrical shorts to happen. Wiring
up the PWR button from the front of the case (two wire twisted
pair labeled PWR and GND), gives you enough control to turn
the system on and off.
*******
On an Asus motherboard, there is a green LED which is wired
in such a way as to monitor for +5VSB. If the ATX PSU is supplying
+5VSB, and the main PSU cable is wired up, the green LED should
be glowing. And the LED should not flicker. It should be
a solid level for the entire time that the switch on the
back of the ATX supply is in the ON position. Asus provides
the LED, to tell you when it is safe to work inside the PC.
The LED must be completely extinguished, before you
work on RAM DIMMs or pull PCI Express cards, that
sort of thing. It takes up to 30 seconds for +5VSB to
drain, after the ATX PSU is switched off.
Paul
