Question PC turns on for split second and turns off

[001Wolf]

I recently installed a new graphic card Gigabyte GTX 660ti on my pc, which had Geforce 210. For a week or so after installing GTX 660ti, it was working fine, but then I had to install a new hard disk on the pc, while doing so the pc stopped turning on. When I press the power button, the CPU fan, PSU fan, and case fan runs for half a second and then turn off again, and further pressing the power button does not run anything, not even for half a second. But half a second thing happens again after I turn off the PSU button and turn it on again and then press the PC power button.

GTX 660ti needs two 6-pin connectors, I have noticed that if I leave one of the 6 pins unconnected to the GPU, the PC turns on.
EDIT: pc still turns on using the old Geforce 210

My PC specs:
Motherboard - DX79TO
PSU - Seasonic 100-240VAC 520watts
16 GB ram RipJaws
CPU - i7-3rd gen
2 hard disks

(Sorry for my bad English; I am not good at technical stuff, but I will try my best to understand the issue and the answers; Thank you!!)

 

[InvalidError]

The PSU momentarily turning on and then not turn on again until unplugged for a while means one of the PSU's protections got tripped and the PSU went into fault lock-out mode to minimize the risk of potential damage.

The most common causes for this are:
1- something is shorting out the PSU
2- the PSU is being overloaded by something
3- the PSU is faulty and cannot cope with the added load
4- a faulty component is tripping the PSU

If the PC "turns on" with the GPU's 6-pins power disconnected, the GPU may be defective and shorting out the 12V rail when 6-pins is connected.

 

[001Wolf]

The PSU momentarily turning on and then not turn on again until unplugged for a while means one of the PSU's protections got tripped and the PSU went into fault lock-out mode to minimize the risk of potential damage.

The most common causes for this are:
1- something is shorting out the PSU
2- the PSU is being overloaded by something
3- the PSU is faulty and cannot cope with the added load
4- a faulty component is tripping the PSU

If the PC "turns on" with the GPU's 6-pins power disconnected, the GPU may be defective and shorting out the 12V rail when 6-pins is connected.

So what could be the best solution for it? Do I need to get a new GPU? Cause the GPU was running fine without any issue for a week, then suddenly it stopped for no reason
OH btw, pc still turns on with Geforce 210

 

[InvalidError]

If the PC worked as-is for a while and still works with the GT210, then you are down to two possible options:
1- the presumably old PSU isn't able to cope with the GTX660's power-on transients anymore or
2- the GTX660Ti is faulty

Try the GTX660Ti in a different PC with known-good decent quality PSU of appropriate rating or try a different PSU of similar or better quality and higher rating in your own PC. If you still get instant shut-off, then something has almost certainly gone wrong with the GPU.

 

[001Wolf]

If the PC worked as-is for a while and still works with the GT210, then you are down to two possible options:
1- the presumably old PSU isn't able to cope with the GTX660's power-on transients anymore or
2- the GTX660Ti is faulty

Try the GTX660Ti in a different PC with known-good decent quality PSU of appropriate rating or try a different PSU of similar or better quality and higher rating in your own PC. If you still get instant shut-off, then something has almost certainly gone wrong with the GPU.

oh okay, I would have to find someone with a PC lol.. it might take some time, so when I actually test, can I reply back to you in this thread, will u still be checking on the messages here? pls 🙏