On Thu, 12 Jul 2018 20:21:03 -0400, Paul
wrote:

wrote:
Need wiring instructions to connect up a motherboard to a desktop PC.
I was hoping to find same for a generic board. I can't find same for
mine. I am doing something wrong.
Thank you
Sammy

The lack of details in your question, aren't going
to give you detailed answers.

There are four twisted pairs for the front panel.

There is a separate pair to run the SPKR beeper. It's not
with the other four pairs.

On an OEM computer like an HP or Dell, the SPKR is a
black circle the size of a quarter on the motherboard,
and doesn't need wiring. That's a "built in SPKR".

Motherboard FPANEL headers can have from 8 pins to 20 pins.

On an HP it might be

x x IDE_LED If polarity wrong, rotate and try again
x x POWER_LED (You cannot hurt the LED via wire rotation)
x x RESET_SWITCH (momentary contact, normally open circuit)
x x POWER_SWITCH (momentary contact, normally open circuit)

On an Asus motherboard, there are pins missing in the
20 pin pattern, for keying or recognition purposes.

Generally +5V and GND pins are separated by enough,
to prevent easy shorting by bending pins. There is a
modicum of safety in the header. Electrically, the
most danger was in some of the SPKR wiring choices.
(I have computers here where the plus SPKR wire is
wired directly to +5V, which is a bad practice.)

*******

On the computer case portion, the wiring harness has a "common color"

x x white,red
x x white,orange
x x white,green
x x white,blue

The message there, is white is the "minus" or "ground" color.

On another machine here, they were a bit more logical, and
made it like this for the front wiring harness. Black
is the common color in this example, and is the "minus"
or "ground".

x x black,red
x x black,orange
x x black,green
x x black,blue

Retail motherboards have a legend next to the pins,
printed in super-tiny white letters.

The front panel wiring "floats". The two switches (the
RESET and POWER switches), neither of the wires is
referenced to the chassis. By doing it that way,
you can rotate the wire pair when connecting to the
motherboard, without incident. The "white" being
minus in that case, is just a convention, and
not an electrical necessity. But, we can always
pretend the manufacturer was a dope, and they
made the white wire touch the chassis too. If
you observe the polarity convention, you should
be OK.

The LEDs are wired to a transistor switch and
a power source/sink. The LEDs float on the chassis
end. The LEDs have a PIV of 5V, and can safely be
reversed electrically without damage. (Note that
not every LED you can buy at Mouser, comes with
that guarantee!) If the LED doesn't light,
you probably didn't connect the "white" wire
to the "minus" pin.

Here is a sample motherboard document, showing
the wiring. Four pairs go to the front panel.
The SPKR pair will only exist on things like
the Asus motherboard, as the HP or Dell will
have a black quarter-sized disc on the motherboard
to do the beeping.

https://s33.postimg.cc/405akh8y7/front_panel_wiring.gif

This information is intended to explain the general
scheme. And is not sufficient if all the hardware
in question is not labeled properly.

Paul

Thanks Paul
You're on target as usual.
Sammy