Smoke after PSU replacement

[Dr M]

[Forgive the humour, its one of my coping mechanisms ]
Problem: During God of war on God of War Difficulty, my computer shut off, no BSOD or anything else. Complete loss of power.
The computer then refused to turn on at ALL. Looked at the motherboard LEDS[The motherboard is a Asus PRIME Z370-A Motherboard]. Saw one white LED, thus assumed it was a PSU issue [over a motherboard].
Solution: Bought a new PSU of the same type non modular,[Corsair CX750M 80 PLUS Bronze 750W Modular PSU]. Watch LTT video on building a computer particularly for power supplies. Install new PSU using the right connectors but didn't change out the fan controller cables etc.
Problem 2: First boot, smoke, flashing and then a small flame. Turned power off and unplugged power cable from the power supplier. LED on motherboard was still going for a couple of seconds after.
Smoke seemed to be coming from the location that the cable labelled CPU was plugged into the CPU[the 8 pin].
Start feverishly googling "PSU smoke"
Now question is what could cause a fault like this? Is it an issue with the power supply (New off Amazon) or issue with the motherboard? Which was then retripped with the new PSU?
[Cough LTT want to do a video on how to safely retrofit and upgrade your computer ]
 

[RONOTHAN##]

Just to confirm, anything that plugs directly into the PSU was not reused, correct? That PSU is semi-modular, so while there are a few connectors that are permanently attached, there's a few that aren't and it's possible that one of those is the issue here. 

 

What it sounds like to me what happened was the voltage to some part of the motherboard was not what was expected. There are a couple different things that could cause that:

1. The PSU was faulty. This could be anything from the PSU cables being incorrectly pinned to there being a short somewhere internally that sent 120V directly to the 12V rail. 
2. The 8 pin EPS was plugged in upside down (hard to do, but not impossible) or the 8 pin PCIe power was plugged into the CPU connector by mistake. 
3. The wrong cable was used. 

A faulty motherboard, while not impossible, seems improbable to me as for it to just happen to have a catastrophic failure as you're replacing the PSU just as a coincidence is very unlikely. No matter what, replace that PSU and hope it didn't kill anything during that event, even if you were the reason it failed I just wouldn't trust it as a short circuit protection should have gone off before you saw flames. Try contacting Corsair and see if they will replace anything in the event that they were killed, though I have heard some horror stories from Corsair's RMA department so good luck on that front. 

[Dr M]

Nothing that was directly connected to the old power supply was used to connect the new PSU.
The new one is not modular [I couldn't find a direct replacement so I went with the next best thing,CX750]. 
We double checked point 2.[I agree its hard but not impossible].
The CX750 has the cables labelled as CPU, so its unlikely to be a wrong cable issue(Unless the cables are labelled incorrectly on Corsairs side)
Yeah I agree about getting it replaced, luckily the computer itself is 7 years old so most components were due an upgrade as they died(rather than before). Hence the PSU upgrade.

Out of interest, How much do you think might be dead?[Also Short-circuit needs more flames and I finally have a use case for GameScent ]
 

[RONOTHAN##]

1 hour ago, Dr M said:

Out of interest, How much do you think might be dead?

The motherboard is the main thing I suspect to be dead. The CPU and RAM are probably OK, though it's not impossible for them to have been killed. GPU and storage are iffy and could go either way. They're probably fine, but you won't know until you get working parts. 

 

1 hour ago, Dr M said:

(Unless the cables are labelled incorrectly on Corsairs side)

This isn't unheard of. I know there was a scandal somewhat recently with one of the major vendors (I want to say EVGA, but don't quote me on that) with the wrong cables for their PSU. I'm fuzzy on the details, but while it would be insanely rare, it has happened before. 

 

 

Also make sure to quote or @RONOTHAN## so we get notifications, I just happened to come back here and see the reply. 

[Failure 101]

Well, your PSU is 100% toast; that's literally magic smoke. I would RMA the PSU, obviously, and I would try to test the other components. If they're broken, I would try to message Corsair about replacing those parts (they may likely say no). So be ready to replace those parts too possibly.

[Renegade042]

Am I crazy in thinking that that shouldn't happen with modern hardware?

I once had an ABIT board, a long time ago, which had a 2x2 power connector and no indication which way

to connect it.  Took me 3 tries and nothing went up in smoke when it was connected wrong...

[Dr M]

1 hour ago, Renegade042 said:

Am I crazy in thinking that that shouldn't happen with modern hardware?

I once had an ABIT board, a long time ago, which had a 2x2 power connector and no indication which way

to connect it.  Took me 3 tries and nothing went up in smoke when it was connected wrong...

I mean I've read the publications on the subject and smoke and fire is typically a catastrophic failure which shouldn't happen nowadays[due to the fact that electrical fires are well, difficult to put out]
I wonder if the voltages running through modern power supplies are much higher, I don't think it was the wrong cable.
I am going to RMA it but also ask an electrical engineer friend of mine what could cause fire & magic smoke but no external damage(no scorch marks etc. its all very strange)