got my printer up and running last night.
I am able to run the controller off the 5vsb and bring the PSU out of standby (D6) with gcode.
Have the PSU cooling connected to D8. Haven't figured out how to control the speed.(PWM}.
Seemed like the cosmos was fighting me all the way.
Had to make a 4 pin, 2mm pitch, 2x2 plug to connect the 5vsb and PS-on. That alone took...well I have 3 of them but the 3rd is the best. The second functions and connects just fine...because of space restrictions, Meanwell's requirements for the PSU and my thought to make a converter plug...so I can utilize my multiple connectors kit I bought...for plugging into the Meanwell PSU...the 2.5mm pitch kit's 2x2 won't/can't/does not want to/did not fit. And the first I had the pins facing, not the best way.
When I realized the kit I bought would not/was not the correct size, I went through my scrap bin of electronics, searching for a 2x2 or a 2x.anything. I even took every thing out to the barn, (Thats what we call the building)
to start picking away at removing the components which are worth more than...a quarter?
After I finished with the third connector, I went looking for...something in that box of "stuff". I-ee can not remember what that was. But the box covered by another box was suddenly un-covered to reveal, right on top, a 2x10, 2 mm connector wire harness, . . . . .I just don't know how. . . .
Yup! I went with the factory made 2x2 connector.
finally at around 7:30 AM, I have the bed level checked. The frame level/spaced very evenly and Cura loaded with my little tripod mount-camera base, loaded and the heat bed starts to rising in temperature....then the extruder...ready to start...and it engages. To bad the filament was not.
Finally got that corrected and restart printing. Up to temp, any second now and 
My laptop was not...was not. I never disconnected the USB voltage. 
And coincidentally at the same point of progress, just before the last PSU went - gone, while using Cura.
I should had been using Repetier-Host and if I didn't want to undo my work on the USB A to A Male cable, (very clean and smooth splice) I could had made another...be much easier than the prior...heck I even thought about installing a switch on the controller enclosure to lift the negative power line on the cable inside.(when you mentioned the issue)
Again, brain overload.
Replacement motherboard will a fraction of what the PSU cost.
Appears to be many for sale...and with the on-board ATI GPU even.
.........partspeople.comhave the best tear down video's...he includes every screw and size.
Removing the hard drive.......now!
