Motherboard? PSU? Or my own dumb?

[DerGolgo]

Hiya.
So this is about my AX1500i PSU, alongside my Gigabyte X388 Aorus Pro.
I had to rebuild my machine after my motherboard died on me. First, trying to find a board with the TR4 socket was... not fun.
Pretty much any time I thought I was making progress, a new problem materialized. Several times, some of the coolant contaminated the surface of the board. I'd clean that up with generous helpings of isopropyl and a brush.

The latest problem materialized after a final, successful trial of the cooling system. 18 hours of operation, no leaks, not even a hint of one.
I proceeded to wire up all the various components and things. And then, nothing happens.
I've tried to isolate the problem by unplugging various components. No help. The "self-test" button on the PSU does nothing.

When the PSU is well and hooked up and switch it on, an LED gives me a single, short flash. The manual does not indicate this LED exists. It' s´located  near the
chipset.
Presently, the flash of light is green.
But it previously was much brighter and much wider and, critically, bright white..
Not only does the manual not mention the LED, I found no mention of the color in the long list of error codres.

The trial run had involved putting a plug on the end of the ATX cable that usually hooks up to the motherboard. The plug did nothing more than to short two specific contacts, to let me test the waterpumps and things without powering up the motherboard and all connected to it.
If that thing is present, all is sunshine an happiness. Well, most. The PSU self-test still does nothing. But it does appear to be supplying power to all that is plugged in.

So did I bust up another unobtanium motherboard?
Or a slightly more common power suppy?

[LadyLucy0]

 Sorry to hear about your PC, Water damage is not fun to fix. Got a friend you can borrow a PSU from? I keep a spare just for testing. One run on the PSU could be damaged and the rest ok, It happens. The PSU is the best and cheapest place to start. Good Luck, And I'm hoping it's the PSU.

[DerGolgo]

Thanks. Water damage to the PSU is actually something I am confident I can rule out.
I've got a plug-thingy that goes on the ATX cable instead of the motherboard. Shorts two specific pins, and the PSU will power all that is plugged in as if it was hooked up to a running motherboard. The idea of this contrivance being to test the cooling system with no life electricity on the motherboard or peripherals.

As for water damage. On the board is probable. Also, is more like water-color damage. I had decided to try a different color coolant, and the stuff was specifically marketed for for cooling computers to low temperatures I would never even get near.
But wherever a drop of the stuff lands and dries, it leaves a pretty sizable deposit of purple gunk that is tricky to remove. And, I suspect, an electric conductor.

Gonna have the PSU tested in a specialist shop tomorrow or Thursday. I won't

[c-attack]

If the 24 pin jumper allows power on, that does suggest the motherboard may be the problem. However, the load with the jumper is limited to SATA/molex devices which is likely about 30W and much less than a normal startup. When you try to power on with the ATX cable on the motherboard, what happens?  Does it startup and then hard power off?  Continuously power cycle? Or absolutely nothing at all — just dead like the PSU is unplugged?

[DerGolgo]

5 minutes ago, c-attack said:

When you try to power on with the ATX cable on the motherboard, what happens?  ... Or absolutely nothing at all — just dead like the PSU is unplugged?

That's the one. When all is plugged in proper, the PSU makes like a brick, and so does the motherboard.
The only anything I can get is an LED on the board flashing once. Not when I try to power up, but just when I flip the main switch on the PSU. Under normal conditions, when all was working, the flash was bright white.
Until the day before yesterday, the only flash I can get now was meek and green. Since yesterday, it's red or yellow. The LED(s) in question are not even mentioned in the manual. They sit more or less on top of the main chipset bits, but seem to be part of a decorative element.

[LadyLucy0]

PSU is the cheapest place to start, Hope the test says It's a brick. Good Luck.

[DerGolgo]

The place I thought could do some testing tell me they can't.
And it appears that the main benefit would be that I don't have to disassemble my whole machine to swap the PSU, while the motherboard would be where this whole nightmare began.
My old motherboard had died on me, and I couldn't find a like-for-like replacement for love nor money. Different brand board I could find, even for a reasonable price. But I had to re-plumb my watercooling. That's two 4x120mm radiators, pumps, tank, all the hoses that go in between.

I got it in my head a different color coolant would be nice - and things went downhill from there.
I install the new board and rebuild everything around it. And am happy my computer works again. And am busy running a backup of a damaged SSD (SATA port broke off, but I found a mobile-phone shop who fixed that well enough that I could run a backup) when the computer stops working.
Confused, I look in, and find a purple puddle on my motherboard. Oh, yeah, I got a Thermaltake Core X5 case, wherein the motherboard lives horizontal, underneath the radiators. Because I'm an idiot.

Eventually, I am able to find the leak. No, it's not one of the barb fittings. Turns out that the thread-insert in the radiator had somehow fused itself to a fitting, and the slightest nudge, like from switching out the hose, had busted the copper metal around it. Just a little, but when I tried to unscrew the fitting... you know how after tight comes loose? Here, trying to loosen it, after loose came tight-ish. The thread insert just spun in the radiator wall but would not be extracted.
And it turns out nobody, not the HVAC crowd, nor garages around here, will fix a busted radiator. It's 90 minutes each way to a specialist company (half blind, so it's all public transport for me).

So I had to order a new radiator. Thinking my clumsy claws had been to blame.
In the meantime, I was able to get the machine running with an ancient air-cooled graphics card.
After the new radiator arrives, and I assemble it all, and I do the trial run (trick the PSU into providing power to the water pumps, without even plugging the motherboard in). Normally, that's supposed to take all night.
Within an hour, the paper towels stuffed in there were soaked and I had to stop it.
Turns out the second radiator, on the CPU loop, had sprung the exact same goddamn leak!

Obviously, not buying the same brand radiator a 4th time. Fool me thrice.
Adequate alternatives would require waiting till July-ish. And after getting the GPU look watertight, I didn't want to disassemble it just so I could run the CPU loop.
New radiator slightly oversized and overpriced, I manage to fit it in. Trial run brings INSTANT purple-rain, and more than ever before.
Turns out the "plugs" on the side I wasn't using, and that the instruction manual didn't even mention? Yeah. Not plugs. Just decorative/to keep dirt out during transit.

I finally get it all watertight, and I think I've removed all the purple residue the shite new coolant was leaving all over the place where a drop might hit something and dry out.

And that's how I got here.

Worst of all: I got a 1500 W PSU not out of sheer vanity. The CPU in full tilt, not even overclocked, will draw 500 W alone. When I had originally built the machine, I had had to conclude that a 1200 W PSU would likely be insufficient. 1500 was just the next step up.

And you know how there's a semiconductor shortage?
Yeah. A new 1500 W PSU will set me back about as much as a new motherboard.
Because ******** my life.

[DerGolgo]

This is what it looks like inside my machine right now.
No, that mess of cables is what it looks like after I've done some clearing up.