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I recently upgraded the GPU of my rig to an Asus GTX 770. My system had a 600 Watts PSU. That meets the minimum requirements of the GPU, and the system works fine with that PSU. But I didn't like the fact that it was running on minimum requirements, so I decided to upgrade the PSU as well. I bought a Corsair TX Series CMPSU-750TX 750W from newegg. I replaced the PSU with the new one and plugged everything in. When I applied power to it, the LEDs on the motherboard and on the video card lit up. But when I press the power button, nothing happens, the system doesn't power on. I then tried unplugging all case fans, HDDs, SSDs, optical drive, only supplying power to the motherboard and GPU, but still nothing.

I had to leave before finishing troubleshooting this, and will only be able to work on it later on, but I wanted to run this by you guys. Could the PSU be DOA, even if power is somehow flowing through it, since the LEDs on the motherboard and GPU light up? Would the paperclip test give me a definitive answer?

Thanks in advance.

Vascaíno

Try the paperclip test but first make sure that the 2-pin for the on/off switch is on the proper prongs in the proper polarity. A DOA Corsair is not out of the question, but would be quite rare.

As Ned said, it sounds like your connection from your motherboard to power button might be off. Double check all of your case/mobo connections so that they are going to the correct pins. If that doesn't work, then start up your PSU checks.

vascaino wrote:

I recently upgraded the GPU of my rig to an Asus GTX 770. My system had a 600 Watts PSU. That meets the minimum requirements of the GPU, and the system works fine with that PSU. But I didn't like the fact that it was running on minimum requirements

1) Don't pay any attention to "minimum recommended PSU" from GPU manufacturers. TR uses a pretty beefy system for their GPU reviews and system power consumption with the GTX 770 was just under 300W. Anandtech uses an even more ludicrous overclocked system and only churned out 380W under FurMark with their GTX 770
2) Use a power supply calculator like this one in the future.

With regards to your issue, I would also check the power/reset leads weren't dislodged during the PSU swap (like others have said).

Thanks for all the responses, and thanks DPete27 for the helpful tips. According to that calculator, my system would require a 470 Watts PSU, and the 600W PSU I have should suffice, but I'm still more comfortable with something that has more headroom for expansion.

I will double check the power/reset leads more thoroughly when I get back, but I did visually inspect them, and they seemed to be in place. I don't know if the polarity is correct though, and if wrong polarity could prevent the PSU from starting up.

The fact that the mobo sense LEDs for power light up tell me the PSU and the mobo are talking, meaning the problem lies somewhere else.

Well, so this was curious... I double checked the power/reset leads. They were correctly connected to the mobo. I then tried the paperclip test and voilà, the PSU turned on. But this kind of worried me that the mobo could have become damaged somehow. So I plugged the old PSU back in and everything worked just fine. Things just weren't adding up... Once again I tried plugging the new one in, but this time I used the other EPS connector (this PSU has 2 of them) instead, and this time it turned on...

So it seems like one of the EPS connectors is bad. Now I'm not really sure if I should RMA or not, since the system is working now, and I only need one EPS connector. If it's just a bad connector, I'm inclined to save myself the hassle of RMA'ing and just keep it since the PSU has a 5 years warranty. But I have this nagging feeling that something else could be wrong with it as well...

vascaino wrote:

So it seems like one of the EPS connectors is bad. Now I'm not really sure if I should RMA or not, since the system is working now, and I only need one EPS connector. If it's just a bad connector, I'm inclined to save myself the hassle of RMA'ing and just keep it since the PSU has a 5 years warranty. But I have this nagging feeling that something else could be wrong with it as well...

OK, I know exactly what happened. The 2 halves of the EPS12V 8-pin connector do not share identical pin-outs or physical connector keys, yet it is possible (and often happens) to insert the "wrong half" in a 4-pin EPS mobo connector. This used to result in magic smoke events but it appears that mobo mfgs have caught on and provided safeguards against this mis-keying.

Captain Ned wrote:

OK, I know exactly what happened. The 2 halves of the EPS12V 8-pin connector do not share identical pin-outs or physical connector keys, yet it is possible (and often happens) to insert the "wrong half" in a 4-pin EPS mobo connector. This used to result in magic smoke events but it appears that mobo mfgs have caught on and provided safeguards against this mis-keying.

Well, I guess I should have clarified that the PSU has 2 8-pin EPS connectors, and the mobo takes an 8-pin EPS, not a 4-pin. Both connectors are labeled "CPU". The system powers up with one of them plugged in, not the other one, leading me to believe one is bad.

vascaino wrote:

Well, I guess I should have clarified that the PSU has 2 8-pin EPS connectors, and the mobo takes an 8-pin EPS, not a 4-pin. Both connectors are labeled "CPU". The system powers up with one of them plugged in, not the other one, leading me to believe one is bad.

Really? The Corsair website for your PSU says it has 1 EPS connector. Are you sure that the other "EPS" connector isn't really an 8-pin PCI-E (of which you should have 4)?

Captain Ned wrote:

vascaino wrote:

Well, I guess I should have clarified that the PSU has 2 8-pin EPS connectors, and the mobo takes an 8-pin EPS, not a 4-pin. Both connectors are labeled "CPU". The system powers up with one of them plugged in, not the other one, leading me to believe one is bad.

Really? The Corsair website for your PSU says it has 1 EPS connector. Are you sure that the other "EPS" connector isn't really an 8-pin PCI-E (of which you should have 4)?

Captain Ned, it appears that Corsair and newegg have yet to update their specs to the latest revision of the TX750, as if I remember correctly it's been around for a while. Newegg photos show two 8 PIN CPU connectors. Maybe one truly is faulty?

Well I'll be. What mobo requires 2 8-pin EPS connectors? The thought that a PSU had 2 was simply beyond my ken.