"Speaker For PC Interanal BIOS Computer Motherboard Mini Onboard Case Buzzer Board Beep Alarm NEW."

Norm Why wrote:
The safety ground on the three prong plug, should be joined to the
chassis ground.

You are allowed to test the system with no SATA cables in place.

You can bring up a machine and enter the BIOS, while no hard drives
or optical drives are connected. This would allow you to observe
system operation as SATA cables are added to a successfully running
(so far) system.

Paul
Thanks Paul,

I've even removed the beep speaker to find the short. Ohm meter says
short is low resistance. Step one in two-page diagnostic troubleshooting
flow chart must be wrong , or it is a bad, bad short.

Assuming Step One was wrong. I carried on down to Plug in Power supply.
Turn power on. No Beep, momentary power, system drops dead. Short must be
real and getting worse, or system is learning how to be more
uncooperative.

The short to ground goes through the 4pin 12V connector.



Did you reverse it ?

The 2x2 has shaped enclosures for the pins,
and they are only intended to fit one way.
The two pieces that form a latch, should be
on the same side.

If a power supply has become weak with age, it
can shut down when less than the rated load
is present.

You'd need a clamp-on ammeter, to easily be able
to make measurements of current flows on the various
rails. For example, if the main PSU connector
has four +5V wires, you put all four within the
jaws of a DC clamp-on ammeter, and the meter
gives the total current flow in the four wires.

For the first 35 milliseconds, the supply ignores
overloads. This gives time for the main outputs to
charge any capacitors present. It's after that
point, that it starts looking for overloads.

I do my initial builds, on the kitchen table,
using a phone book as an "insulating base". Once the
components are proved working, then I start installing
the stuff in a computer case. and this gives an opportunity
to compare symptoms between "insulated" and "grounded".

Paul