Question Computer Shut down

Jul 30, 2021
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GPU : R9 380 GAMING 2G


Hello. I was playing game, all the sudden Computer shut down. When I try to power it back, powers comes for 1 second and shuts down again.
I thought it was Power Supply issue so since it was still under warranty, I sent them to fix. However, They said there is no problem with Power Supply.
I tested turning on computer without my graphic card and unplugged power connector from GPU. It turns on.
When I tested with other graphic card from another computers, it turns on. So I guess there is nothing wrong with Power supply.
When I tested again with plugging power connector, it powers on and shut down after 1 second...
Any Suggestion ? or Do I need new GPU.
Thank you.