Many clone computers have power supplies that even violate defacto standards of 30 years ago. One simple way to see this. Put an AM radio next to the power supply. Radio will suffer interference if power supply does not contain one essential and required function.

Your power supply is a system that involves three parts - switch, motherboard controller, and PSU. Which has failed? That is the purpose of the meter. First, something between 4.87 and 5.25 VDC must appear on the purple wire. This power is always on for the motherboard power supply controller circuit on motherboard. That power probably does exist because of the more than 2 volts on the green wire. Green wire of more than 2 volts tells power supply to not power up.

When the switch is pressed, motherboard circuit shorts the green wire to near zero. That causes power supply to turn on. If essential voltages (3.3, 5, & 12) can be maintained, then power appears on corresponding orange, red, and yellow wires. But if something causes any one of these voltages to not remain in limits, then all voltages are turned off.

You should be able to see all this with the multimeter and without buying any power supply. IOW first identify the defective component with the meter. That means even monitoring that push button switch properly connects and signals motherboard only when pressed.

All power supplies have internal protection - that makes anything adjacent to that supply redundant. However, many buy power supplies only on price. Therefore they must spend $hundreds on peripheral protectors that were already suppose to be inside the power supply.

Any external protectors that were going to protect your hardware are located at the service entrance. Of course that means your building must have earthing that meets or exceeds post 1990 NEC requirements. And every incoming wire must connect to that single point earth ground either via hard wire (CATV and satellite dish) or via a 'whole house' protector (telephone and AC electric). This protector is so effective and so inexpensive that the phone company routinely installs same at every customer interface. But again, it is only as effective as that single point earth ground.

Earthing at the service entrance means internal power supply protection will not be overwhelmed. But first the power supply must have such internal protection. Minimally acceptable power supplies are about $70 retail. Some may be discounted. But those $40 power supplies are routinely missing essential functions that were standard even 30 years ago. Functions that Intel specs demand. Functions that are routinely missing is discount clone computer power supplies.

Provided is how to find reasons for failure, how to avoid future failures, and how to buy a minimally acceptable power supply (if necessary).

Posted by: w_tom <w_tom1 at hotmail.com> to cakewalk.audio