Optiplex 7040 - PSU swap now power button won't work

If you changed the AC recovery setting and it didn't "stick", assuming you saved the change before exiting BIOS setup, then I'd replace the motherboard battery before going any further.

Battery may have croaked while you had things unplugged and disassembled to swap the PSU. The battery is needed to hold BIOS settings changes when there's no power to the motherboard, eg when you switch off at the PSU switch. In the absence of a working battery, BIOS settings revert to the defaults, which for AC recovery is probably "do nothing" or "disabled".

"-I swapped the 180w PSU for a 24pin 600w PSU

-Repined to 8 pin MB connector" if you made a mistake with even 1 pin you probably fried the cpu and motherboard and you are DONE!

This isn't a passive move.  You need the ModdiY adapter.

7040 MT requires Adapter cable and EPS12v power supply.  MODDIY CAB359  cable or equivalent.

This is not however supported by Dell.

https://www.moddiy.com/products/Dell-OptiPlex-7020-PSU-Main-Power-24%252dPin-to-8%252dPin-Adapter-Cable-%2830cm%29.html

Someone has already tried this and it works.

http://en.community.dell.com/support-forums/desktop/f/3515/p/19986195/21009213

EVGA Super nova 700B1 or 750B1 works fine.

https://www.amazon.com/EVGA-SuperNOVA-Modular-Warranty-110-B1-0750-VR/dp/B00K85X23O

https://www.amazon.com/EVGA-BRONZE-Warranty-Tester-100-B1-0700-K1/dp/B018JYHBE6/

First, I fined it odd you seem to have glassed over the beginning sentence of my post.

The computer is operating 100% fine. In fact I'm writing this reply on it right now.

Run multiple stress tested on it with the new 1080 I installed.

It's not "you probably fried the cpu and motherboard and you are DONE!"

READ THE POST!

Really all I need to do is wire in a button to the green "power on" PSU wire and I'd be in business.

I'm trying to understand the issue, whether in gets solved or not won't inconvenience me.

Second, I know how to use the search function.

The ModdiY adapter is what my re-pin is based off of. Confirmed with my own voltage tests.

There is nothing magical about the adapter or electricity.

You can buy an adapter or knock out the pins and do it yourself.

3 12v lines. 1 adopted from a molex HD connector

3 grounds

1 power on

1 power good

If you want to help, help with the questions I've asked.

Or read the post and make better assumptions then "He's an idiot that can't use the search function".

First - I can power the computer on by grounding the green (power on) lead on the 8 pin MB connector. Computer powes up, runs great and I'm having no issues with it operating. Events to this point: -Computer was working great with no issues. -Power button was working just as it should. -I swapped the 180w PSU for a 24pin 600w PSU -Repined to 8 pin MB connector -Went to power on with the button and got nothing. -Grounded green wire, computer powers right on and boots -Tried to ground out power button pins and got nothing -circuit tested every power button pin to the pin the green wire plugs into, none went threw. -Power button LED working when powered on -Power Button will turn Computer off when pressed while on -Changed setup to power PC on when AC power is lost so i could use the switch on the PSU but computer wont power on when I cycle the power switch. Setting did save in setup Anyone have an actual pinout of a 6 pin/5 used power button connector? Is there something I'm missing here? Any other testing point to find out where the fault is? Is there a jumper somewhere that may have fallen off while I was messing with it? computers running great and I can't turn it on and off, so frustrating. Any help is appreciated.

Dell won't give you that info you'd have to map the power button yourself. Not only that but I believe the power button plugs into the I/O board with the USB connectors. I think if you'd used the adapter SpeedStep suggested this would not be a problem. Also, you don't need a power switch to turn off the PC just go to the Shutdown option on the operating system. And to power on the PC, you'd need to do your wire grounding method.