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Somebody forgot the isolation under the pcb?
Been some years since I took apart a psu, but there used to be plastic isolation sheet between the pcb and the metal case.
I think he means without that isolation sheet the board is connected directly to the casing and shorted out. Of course, that should have been grounded too so I'm not sure.
If it shorted on the 12V side it can pull a ton of amps (it says 60 amps max at 12V) and melt through the casing and start fires pretty easily without tripping a breaker.
Probably. I think if this was after the rectifier, the rectifier would have acted like a fuse, getting you a single loud pop instead of a few seconds of arcing.
It's definitely somewhere on the primary side though.
Something between the power switch and the thing that makes the wall power into PC power wasn't made right, and wall power got somewhere it shouldn't go
What happened is pretty simple, mains wires poked through the board, weren't trimmed after soldering, weren't blocked by an insulating sheet, and touched the case: https://i.imgur.com/SLsQmmu.gif
The discussion above is about why other possible failure modes are unlikely. After getting on to the board, the power goes through some filtering and protection circuitry, then through a rectifier(4 diodes in a single package) that turns the high voltage AC into high voltage DC. Then the high voltage DC gets chopped up into much higher frequency AC, before going through a transformer to drop it down to low voltage high frequency AC. This then gets rectified to 12v DC before getting converted to the other voltages. Usually anyway, there are other ways to design a power supply, and there will be a separate similar power supply just for 5vsb(this is always on, so your computer can turn itself on when you press the power button).
Anyway, back to the rectifier, semiconductors often have relatively thin bond wires connecting the silicon die to the rest of the package, that would get vaporized in a few milliseconds if you tried to push this much current through them. This board also has an actual fuse, but the short happened before the power got that far.
This PSU turned into a cheap momentary welding machine, and modern inverter welders use capacitors to do the same thing. My guess is 12V rail shorted @ 100-150A, which isn't too far off from welding machine parameters. It's why their circuit breaker didn't trip either, probably still being under 1800W or less from the wall.
They should be turning the IEC cable on from a switch, not plugging it in live from the unit. They should have a circuit-breaker and GFCI inline, and a dim-bulb tester, or at least variac they can slowly dial up.
Also possible this was plugged into a 220V line while the little red switch was set to 110V but I'm not sure if those typically catastrophically fail like this.
Was watching a video the other day and the guy was like "I don't trust these PSUs with a 110/220 switch, they're almost always low quality" and I was like "WTF they all have that". Start looking around and, uh, yeah. Well then.
Gotta say, great reaction time. Personally I'd have gone for circuit breaker and fire extinguisher. Safer option. But I've had that drilled into me and never had to put the training into practice so I can't say for certain if I would have done different.
In Europe, it's normal to have a row of sockets in front of the desk, with their switches and fuses/circuit breakers, to prevent a short circuit in one workstation from affecting the others. It seems very strange to me to test anything electronic with the socket under the desk...
Had this exact same thought... Couldn't remember exactly what I had because it's been so long and my PC has a shroud over the PSU but thankfully the box doesn't 😮💨
Uh? That's weird... I've had the EXACT Corsair CX 750 fail like that, and it was the only time I've ever seen it in over 20 years of using PCs (and hopefully it stays like that). It was my spare/backup machine, which I hand't used in a while. When I powered it up it blew the fuse of my surge protector, then I replaced it (surge protector) for another one and the PSU lit up exactly like this video.
Many many years ago, I got a call to fix a computer that wouldn't boot. I go into the bios, see it doesn't recognize the hard drive. I was prepared for an HDD failure, so I replaced it with one with a fresh image, and go to boot, and nope, failure. Maybe my drive was bad? I put my second one in, and when I go to boot it, there are sparks. I tell my boss the PSU has issues and it fried a couple hard drives.
He tells me that's not a thing, drives 30 minutes to the site with a fresh hard drive, and gives me this "now check this out" smirk as he turns it on and the magic smoke escapes a fourth hdd.
When I went to RMA the PSU, it of course got rejected. I elevated to a manager, and told him it had fried too many drives already. After some back and forth, he agrees to "run some tests."
So anyway, I'm pretty sure that PSU got at least 5 HDDs, and maybe a voltmeter? I did eventually get it RMA'd.
Was it a modular power supply? Recently fried an SSD by just grabbing a SATA power cable out of my box-o-shit-cables and plugging it in, turns out different manufacturers use different pinouts on the PSU side, even though they have the same keying...
They claimed that the warranty doesn't start from date of purchase, but date of manufacture (2022).
That's really scummy. I've only heard of manufacturers going by the manufacture date when the customer doesn't have a proof of purchase to verify the purchase date so they still offer to cover it under warranty as long as the manufacture date is within that time frame.
I build computers from parts for friends and family. You know who I'm not going to buy from in the future when it comes to motherboards or other parts?
This is why PSUs are the one thing you should never skimp on in a build. Every other component of a PC can fail pretty badly, but chances are you’ll only be replacing that component.
If your PSU fails badly enough, you’re replacing your PC and your house.
I've had two PSUs fail in the last 20 years and neither damaged any PC components thankfully. One of them blew a cap and then the cap casing shorted in the PSU much like this video. It was very violent. Replaced the PSU and it booted just fine. So even if they fail, a decent PSU will usually limit damage to itself. Though a Seasonic etc will be way less likely to fail in the first place.
u/Shoukyaku Ryzen 7 9800X3D | RTX 3060 Ti | 32GB DDR5 600020h agoedited 1m ago
Real and fking true. This is the one single tip I tell my friends whose PCs I’ve built for them, which is to never, EVER, skimp and cheap out on PSUs out of all the components. The difference between the two is that:
- you pay extra for a better PSU and get a PC devoid of any electrical problems for a decade or longer, and you can use it for future PC builds with zero worries
OR
- you skimp and cheap out on the PSU and your PC decides to say “fk it” at a random moment at any time, and it bricks itself alongside multiple components of your PC, or decides to become an arsonist and burn your whole house down along with it
So far, every friend of mine heeded my tip, and 4-5 years later (for more than half of them), they have yet to experience any electrical problems or mishaps, and some even managed to upgrade from AM4 to AM5 pre-RAMpocalypse w/o changing their PSUs.
Power supply caught fire in his rig while he was playing WoW or something. He unplugged everything and carried a flaming PC outside rather than ruin everything in it with a fire extinguisher.
Nuked the graphics card, but the mother board and memory ended up being okay. Manufacturer of the power supply took responsibility and paid to replace it all.
But never again have we left a computer powered on while we're not home.
CO2 extinguisher, they aren't as effective on all kinds of fires like ABC powder or foam, but they are much much less likely to cause collateral damage
Was going to say, last time I saw something like that was when I thought a power supply was auto-switching and plugged it into a customer’s machine. Turns out it was manual, and had been on 110 power as we are in the US (industrial machine was stepped up to 220).
What kind of trash PSU explodes into flame over that though? Every one ive ever seen blow from that just makes a loud pop and starts breathing the mysterious blue smoke of death.
I don't think that's the case. The PSU (VSP Megamax) doesn't have the voltage switch as it has active pfc. In fact, most PSUs can adjust the voltage accordingly.
In fact, most PSUs can adjust the voltage accordingly.
Plenty of cheap PSUs that don't have active PFC and require you to set the 110v/220v switch properly. That said, they are becoming rare enough that it isn't something that you would think to check these days...
I’ll save you. He should have dug his hand into that fire real deep and showed it who’s boss. Although he did the next best thing and unplugged the cable at the firey end.
I like to think I remain pretty level headed in high risk situations, which is usually true.
However, one time I was heating up a pan with oil to cook stuff, but the stove top thermostat was apparently broken and what should have been a very low temperature went to glowing red hot as quickly as it could, past what it should be limited to even at max settings.
While I stepped into the pantry to grab some of the stuff I was planning to cook for a few minutes, the oil caught fire and the range top which the property owner had used for years without cleaning, also caught fire.
I am well aware that you don't put water on oil fires. Yet in the heat of the moment I instantly moved the pan to the sink and put water on it.
Thankfully past that point my brain started functioning normally and I put a lid on it, called the fire brigade and went outside to turn the power off.
But it was insane to see how all logic went out the door the moment I saw a fire in the house that wasn't meant to be there.
People on the internet really like to think they’re some entity of pure will inhabiting a physical body, as if they aren’t an ongoing chemical reaction whose thoughts and behaviors are just as physical as their muscles and bones.
This is why my test bench setup has the power strip on top of the table with it. After seeing this clip I might even throw a fire extinguisher down there with it also lol.
Was my first thought too, but it appears the cables goes off somewhere behind and under the desk. Other end might not be easily accessible, definitely could use some safety improvements lol. Lucky it didn’t ground to the casing and electrocute him.
My brother in Christ, the PSU lit up like a god damn firework. You’re telling me you would have the presence of mind to shut it off in the safest/most effective way possible, as opposed to just getting it shut off ASAP so it doesn’t burn the whole fucking place down?
This just happened to me. I was playing some gta5, left the thing ln pause and went to the kitchen to get some snacks. Heard two pop noises and went back to the computer and shit was almost on flames.
You can see the cable goes under the desk and probably isn't super accessible, although I'd still have dived under the desk before grabbing something that might have just been charged with straight wall power.
If this is a service centre (which they look to be a small repair shop) their test bench is appalling imo, no insulation mats, and the power switch isn't easily accessible. Can't see a fire extinguisher either assuming it's not in the room somewhere else
I scrolled down to read some comments and didn't realize the video looped, so when I heard the sound again I thought the dude plugged it back in to give it another try.
This is the kinda reason I never cheap out on a PSU, knowing full well I may be overpaying. I do NOT want this scare. Ever. Never ever ever never ever.
I remember this happening once at a 800 person lan I attended back in the 2000s. Someone was using a cheap knockoff PSU and it blew about halfway through the first day. It killed every other pc at that table. I was, thankfully, 2 tables over. The sound was sure spectacular!
I recently salvaged an older power strip with individual power switches per plug and a friend of mine was like 'but why'. This is why.... ain't no way I'm grabbing the cord/PSU to pull them apart if it was blowing flames mere seconds ago. IDK if that PSU cage is now shorted right to the AC.
Fix your earth connection, use a power plug that has one. You are lucky that it was a short. Otherwise your body would have been the passage for the current to earth.
Test your the RCD fuse of your building/shop. If the current was to flow through your body to earth, RCD would have bene the only failsafe to save your life. They usually have a test button. Try it.
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u/PCMRBot Bot 4h ago
Welcome to the PCMR, everyone from the frontpage! Please remember:
1 - You too can be part of the PCMR. It's not about the hardware in your rig, but the software in your heart! Age, nationality, race, gender, sexuality, religion, politics, income, and PC specs don't matter! If you love or want to learn about PCs, you're welcome!
2 - Think owning a PC is too expensive? It's cheaper than you may think. Check http://www.pcmasterrace.org/builds for our famous builds and ask for tips and help here!
3 - Consider supporting the folding@home effort to fight Cancer, Alzheimer's, and more, with just your PC! https://pcmasterrace.org/folding
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