Question Is it possible I destroyed my PSU by using a wrong CPU cable?

PhantomR

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Jun 18, 2017
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I have a Corsair RM550x, which is a modular PSU. I was having trouble starting my PC (details below), so I tried using a different CPU cable from another PSU. I thought that if it fits, it should be ok. However, as soon as I started it with the other cable, my PSU made some sound and never started again. Using a multimeter, I found out that the PSU's original CPU Cable, a Corsair Type 4, had the top row of the PSU connector mapped to the bottom row in the motherboard connector and vice versa. However, the cable I used had a different layout: the connectors matched top to top and bottom to bottom. Since the rows esentially correspond to 12V and Ground, respectively, the end result must have been that I flipped the current direction to the motherboard.. could this have really destroyed my PSU? Doesn't the motherboard or the PSU have diodes preventing accidents like this or anything? I am asking because I sent it over to warranty and the people there said it is not fixable and they could refund it.. however, I feel guilty getting a refund if I was the one who destroyed it in the first place because of my stupidity.

Details on why my PC would not start up: I would get the GPU Debug LED on the motherboard lighting up very often, followed by beeps. Turns out the main problem must have been that my GTX 1070 needed a FIRMWARE UPDATE :)oops:) for supporting DisplayPort 1.4.. after installing that, I am now (using a different PSU) only rarely getting beeps (which might indicate there is indeed some problem with the GPU or maybe motherboard, but I didn't really bother with it..).

EDIT: Should it matter, my components are: an Asus GTX 1070 Turbo GPU, a Ryzen 5 1600 CPU, an MSI B350 Tomahawk Motherboard, my case has 5 fans and I have a DVD/RW unit, an M.2 SSD, a SATA SSD and 2 hard disks.
 
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PhantomR

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Jun 18, 2017
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Thank you very much for your help.. I am really wondering: couldn't the motherboard and/or PSU manufacturers just use diodes to prevent this from happening? I remember looking on the back of the motherboard and I think I did see some diodes on the rails coming from the CPU connector, but I am no electronics expert, so I might have made a confusion.

Also, I've just remembered that (being the 'smart' man I am) I also tried using the Corsair's cable in the other PSU. That one did not blow up.. it just wouldn't start, but worked after I put its cable back.. isn't that strange?
 

Eximo

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There are generally protections built in for plugging an 8-pin PCIe connector into the 8-pin CPU additional power, since that is a common and easy mistake to make. However, what you did is different. Swapping in a cable from another power supply means you were putting ground or 12V in a completely different configuration that would be hard to predict. If there was no direct short, than the PSU would still turn on and deliver power until something catastrophic happened.

Putting diodes everywhere would be inefficient and expensive, you would then have to account for the voltage drop across each diode and the power each diode would dissipate even in the forward direction. But they are placed on fan headers and some of the front panel I/O to help protect the system from inadvertently putting things in backwards.
 
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PhantomR

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Jun 18, 2017
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I understand.. I did not consider the case of other, more interleaved configurations. In my case, I am certain the only issue was swapping the 12V pins with Ground pins, as a I checked the cable configurations using a multimeter. Could this have lead to any short per se?
 

Juular

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Can't say what exactly would happen if you reverse 12V and ground but apparently, as evident by your case, it could cause a PSU failure, and you'd be lucky if the PSU is the only part that died.
 

artk2219

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I have a Corsair RM550x, which is a modular PSU. I was having trouble starting my PC (details below), so I tried using a different CPU cable from another PSU. I thought that if it fits, it should be ok. However, as soon as I started it with the other cable, my PSU made some sound and never started again. Using a multimeter, I found out that the PSU's original CPU Cable, a Corsair Type 4, had the top row of the PSU connector mapped to the bottom row in the motherboard connector and vice versa. However, the cable I used had a different layout: the connectors matched top to top and bottom to bottom. Since the rows esentially correspond to 12V and Ground, respectively, the end result must have been that I flipped the current direction to the motherboard.. could this have really destroyed my PSU? Doesn't the motherboard or the PSU have diodes preventing accidents like this or anything? I am asking because I sent it over to warranty and the people there said it is not fixable and they could refund it.. however, I feel guilty getting a refund if I was the one who destroyed it in the first place because of my stupidity.

Details on why my PC would not start up: I would get the GPU Debug LED on the motherboard lighting up very often, followed by beeps. Turns out the main problem must have been that my GTX 1070 needed a FIRMWARE UPDATE :)oops:) for supporting DisplayPort 1.4.. after installing that, I am now (using a different PSU) only rarely getting beeps (which might indicate there is indeed some problem with the GPU or maybe motherboard, but I didn't really bother with it..).

EDIT: Should it matter, my components are: an Asus GTX 1070 Turbo GPU, a Ryzen 5 1600 CPU, an MSI B350 Tomahawk Motherboard, my case has 5 fans and I have a DVD/RW unit, an M.2 SSD, a SATA SSD and 2 hard disks.
Let us know if your other components are in working order when you replace that power supply, hopefully its just the PSU thats gone. As for the warranty, honestly don't sweat it, you didn't do anything malicious and if they're gracious enough to swap it out for you or refund you then just take it, you don't know if the power supply was starting to fail anyway and there are plenty of people that do far worse and still try to RMA items.
 

PhantomR

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Jun 18, 2017
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@Juular , @Zerk2012 , @artk2219 : First of all, thank you for your help. I did use and am currently using a different PSU (even the one whose cable I attached to my now-broken Corsair) and the components work fine. I even overclocked my CPU, GPU and RAM. The only issue still present after doing the firmware update to my GPU is that from time to time my computer cold boots with the GPU Debug Led + beeps, then restarts, then works just fine, so I didn't give it much thought..

Also, thank you, @artk2219 , for encouraging me to RMA :). Really wonder what those worse things are, haha.
 

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