Could I have blown a brand new power supply (PSU) from other fried components?

It could be 1, your PSU was a DOA which is highly unlikely. It sounds like some components are faulty. Check and see if you can get a replacement for that PSU, and run it on another system if possible to make sure it works. Thats very odd, keep me posted.

Even ATX specs define what a power supply must do. For example, power up a PSU with all outputs shorted. Even that short circuit must not damage a PSU. The load cannot damage any properly designed PSU. And a properly designed PSU must not damage the load (motherboard, disk drives, etc) even when it fails.

Little can be concluded without numbers. For example, a power controller decides when a PSU powers on or off? Did you know of the power controller and that a PSU is actually two separate power supplies? Without numbers from a meter, then only speculation is possible.

No 'stored surge' is in a motherboard. That series of events seems strange, but leaves many assumptions unstated. For example, was a paper clip test conducting while connected or disconnected from the motherboard? Best information on power 'systems' (more than just a PSU) means numbers from meter using some requested instructions. Only then can a reply discuss the entire power system.

Without numbers, then replies can only use expressions such as "it sound like" or other speculations. Definitive answers (and why that failure exists) are possible only with a meter.

Again, your conclusions are not based in what is; are based in what should be.

Not having a meter is irrelevant. Meters sell for less money than a hammer. Meters are ubiquitous.

Again, nothing on a good or bad motherboard can damage any properly designed PSU. If a built up surge exists, then where is a motherboard part that stores that much energy? It does not exist. Without numbers from a meter and instructions, then nobody can provide an informed answer.

Its can get expensive if you do not spend much less money on a meter - to learn what is defective before fixing anything. Shotgunning is typically the most expensive repair strategy.

Stop worryng about something that could have occured 500 times. If damage was to happen, it occurred already and in microseconds. Put everything back to original configuration. A meter will not say anything useful until you read exactly what was posted: What were you going to do without first reading each sentence as posted - without requesting instructions? Nothing.

Literally, you must request instructions, as stated repeatedly, before ... well ... that is the point. Stop assuming.

You took meter readings that say nothing useful because you assumed rather than read what was posted. So meter readings say nothing useful.

Restore everything as when the computer worked. AC power cord connected to a receptacle. Computer not on. Set a digital meter to 20 VDC. Attach its black probe to the chassis.

Locate a purple wire (pin 9) from the PSU to where it attaches to the motherboard. Use a red probe to touch that wire inside a nylon connector that attaches to motherboard. If necessary, make that connection using a needle or paper clip. It should read somewhere around 5 volts. Record that number to three digits.

Next, do same with a green wire (pin 16). Then press computer's Power On button. Monitor how meter changes and what it eventually settles to. First number should be something well above 2.6. Second number should be something near to zero, Actual numbers and time to change (behavior) are relevant.

Repeat same to a gray wire (pin 8). Note a higher starting voltage, a lower final voltage, and its behavior. Report those three digit numbers and behavior.

Setup computer to execute as much software as possible. IOW it should be outputting sound loudly, while searching the disk, while playing complex graphics (ie a move), while powering a USB device, while accessing the internet, etc. Having it access many peripherals simultaneously is important. If it cannot power up, then monitor any one red (pin 4,21-23), orange (pin 1,2,12 or 13), and yellow (pin 10 or 11) wire for what each does as and after its power button is pressed.

Report all three digit numbers from those six wires. Next reply will identify or exonerate suspects.

BTW, if wires are not colored, then a PSU may not be ATX Standard. See www.smpspowersupply.com for color and pinouts.

First reading was from the purple wire. A power system is actually two completely different power supplies. Purple wire is power for a computer referred to as a 'power controller'. Without something approaching five volts. then we have an anomaly to trace. Let's follow that evidence.

Disconnect an AC power cord before making or breaking any connection so as to not damage hardware. Then unplug that maybe 24 pin connector from the motherboard. Attach meter's red and black probes to that purple and any black wire. Then reconnect the AC power cord. What is that voltage - all three digits are significant.

What we can conclude from your first test: If that purple wire did not have a voltage, then a motherboard short or power supply defect exists. If 5 volts appears, then a motherboard short exists. If 5 volts still does not appear, then power is not entering, being regulated by, or coming out of the PSU. That test determines where a failure is on the left side (motherboard) or right side (PSU or its AC power connection). IOW we are now 'following the evidence'.

Another power supply inside that PSU might be perfectly good. At this point. we do not care. We are simply concerned with a smaller supply that must provide 5 volts on the purple wire. To determine if that smaller supply or the motherboard has a defect. What number or voltage movement does that new test report?

OK. A power supply is actually two separate supplies. Purple wire connects a small supply to a computer that controls power. That 5+ volts is perfectly good. So the power controller is operating properly.

Green wire is that computer ordering the PSU from off (4.59 volts) to on (0.03 volts). So the power controller sees a front panel power button request a power on.

Gray wire is a voltage monitor that (at 0.02) tells the power controller that it never sees proper values on critical voltage wires.

Now to look at another power supply inside that PSU.

Apparently the 12 volts (yellow wire) sees an initial attempt to provide power. Then cuts off when some other voltage (apparently) does not meet required values. 3.3 volts (orange wire) also sees some attempt.

But the 5 volts (red wire) never gets started. Apparently the power controller was told voltages are bad because 5 volts never gets started. BTW, very useful descriptions for the red, orange and yellow wires.

Suspects on 5 volts are power supply or its load. Either PSU has a defective 5 volt regulator output. Or a short somewhere on the load (motherboard, disk drive, GPU, etc) causes 5 volts to never get started. We know what voltage is defective. Now decide if the defect is on the load (left) or PSU (right). This is where we draw a line between suspects to discover a failure on the left side or right side.

Disconnect AC power cord. After a few seconds, disconnect all other power wires to disk drives, GPU, etc. Also temporarily disconnect that GPU from motherboard. IOW only power connection should be to the motherboard. Restore that AC power cord. Set the meter to measure that 5 volts and press the power button. If any formally attached device was defective, then the 5 volts should rise (or at minimum rise for only a second). If not, then only remaining suspects are motherboard or PSU.

Again, remove AC power cord and delay. Then disconnect that 24 pin connector. Restore AC power cord.

This time, connect the meter to that connector (and PSU) red wire to red probe; any black wire to black probe. Using a paper clip, short the green wire to any black wire. Paper clip is now ordering PSU on (as the power controller once did). If that 5 volts shows a response, then the PSU may be good - numbers and behavior are important. A good PSU implies a short circuit on the motherboard.

If that 5 volts does not move, then we know (without doubt) that the 5 volt regulator inside the PSU has failed. BTW that would be rather unusual because 5 volts and 3.3 volts often share a common regulator. IOW I am betting that short was on the motherboard.

Obviously, this procedure assumes most likely responses. If disconnecting disk drive and GPU result in good voltage, then procedure changes from what is above. But this provides enough to accomplish something - maybe half of what was posted. Or if lucky, all of what is posted. Report back to get a modified procedure or to learn more about what exists.

Again, those numbers say the PSU is ordered to power on. But a 5 volt output (red wire) has problems - either a defective regulator inside the PSU or a short circuit elsewhere in computer's 5 volt bus or 5 volt peripherals (ie disk drives)

Apparently the 5 volt regulator circuit in that PSU is defective. I might open the PSU to determine what part has failed. But that cannot be done by this channel.

We know PSU has good incoming power - purple wire has 5 volts. But the other power supply (red wire 5 volts) is defective.

Don't remember. Did you have other failed supplies? If it also has same symptoms, then a pattern exiss. Then an interesting (and confusing) defect exists.

Did you not connect a second PSU to that system? Use same procedure to learn if that has a similar failure.

Damage occurs in microseconds. If a motherboard caused PSU failure, then any PSU connected is already destroyed. Meanwhile, nothing in the load can damage a properly designed PSU. No damage due to so many features including over voltage protection, over current protection, and fold back current limiting.

Collect evidence using previous supplies using the same procedure. Meanwhile, no 'controlled' installation is possible. Either a supply works or it protects itself. Test with those older supplies first so that system remains least unchanged before connecting a new supply.

ATX specs even describe how to short all PSU outputs together - to test each PSUs self protecting functions. PSUs are required to be unharmed by the load.

Ground is any black wire on that 24 pin connector or on any disk drive four pin power cable.

Purple wire (from the first and smaller power supply) successfully powers a power controller. Power controller powers that green wire. Green wire is a signal for the PSU to power on. Power controller (via green wire) is properly asking for a second (larger) power supply in the PSU to power on. But that larger supply is not providing 5 volts. Therefore all voltages (3.3, 5, 12, -12) are powered to protect anything that is powered by multiple voltages.

Often a fan is powered by the -12 volts - a different voltage. That one is not critical. But that also is part of the second (larger) power supply and therefore remains off after an initial attempt to power on.

Most failures are due to manufacturing defects. Unusual to have two PSUs both with such failures. But symptom is why the second supply should be tested to find a similar (unlikely) defect.

When the green wire asks a PSU to power on, then PSU tries to for up to 2 seconds. After two seconds, if proper voltages are not obtained, then PSU powers back off. That is what you have seen. I do not know why adding the second HD causes that reaction to change. Bit fpr now, only be concerned with the power 'system' and removing anything (shorted/failed) that might cause the power 'system' to not boot.

This would be an outrageous suggestion. But 12 volts in that one drive may be partially shorted to its 5 volts creating enough 5 volts to other parts; to actually try to start for a second or two.

Some background. Disk drive, for example, has two voltages - 5 and 12. If at any time the 12 volts goes less than 5 volts, then hardware damage can result. Circuits exist so that 12 volts is always at or higher than the 5 volts. You could measure this with a meter. Put the red probe on a yellow (12 V) wire. Black probe on a red (5 V) wire. At no time during a power up should that measured voltage every go negative - meaning 12 volts is less than 5 volts. It is a long shot. May not provide useful information. But easily observed and demonstrates another of so many safety features in every PSU.

Informative would be that second hard drive as an only connection to that new supply. Does it cause 5 and 12 volt numbers to change? If working properly, it should not. If some kind of leakage exists between 5 and 12 volts, then numbers may change slightly. Although I would more expect that leaky disk drive component to get hot. Still it is worth trying since it is so convenient right now.

Another possibility. Maybe 12 volts is shorted to the 5 volts inside that disk drive. That higher voltage would trigger over voltage protection on the 5 volt regulator - intentionally shorting out (red wire) 5 volts. Then all other critical voltages must shut down. This would happen too quickly for a meter to see it. But it does explain some of your previous symptoms.

This type failure does not cause damage in a properly designed PSU.