27” iMac power supply repair

Mid 2011 27” iMac A1312 EMC 2429 I would leave it in sleep mode. One day I tried to wake it up and everything about the Mac was dead no response. iMac was plugged into surge protected power strip and devices plugged into power strip works fine. Decided power supply in iMac was bad. Ordered new power supply from iFixit P/N: IF174-000-1. Removed iMac front glass and screen noted when replacing power supply that the part shown online visually matches the old power supply in iMac, but new part doesn’t visually match. Double checked part ordered and part received as it relays to computer specs and configuration finding right P/N ordered and received. Thinking new part is third party version went ahead and installed part. After getting iMac reassembled found iMac chimes and starts to boot up, stops then starts chimes and reboot again then boots up. Then login screen comes up. I put password in and desktop is shown for about two minutes then the screen turns off. Durning the two minutes of screen on time the mouse moves put you can not click on anything. You can get the screen to come back on by tapping power button or keyboard but same two minute issue. Any thoughts, any suggestions.