Hello,
I have a CUH-20xx PS4 Slim (SAD-001 mainboard, ADP160-CR power supply) I got on the cheap due to a non working Blu Ray drive. It had been opened before it got into my hands, so I’m not sure what could have been done to it. First time working on one of those so learning as I search for things.
After replacing the disc ray drive failed fuse, I started playing a (digital) game for about an hour, before realising the console had a pretty bad intermittent coil whine. At some point in my attempts to figure out where the noise was coming from and why, the console stopped powering on at all. One beep with a blue light for a second at the first press, and that was it.
Turned out the power supply had failed (no 12V when shorting the two pins), so I got a known good replacement one.
With the good PSU, the console still doesnt start (one beep, then nothing until I unplug). On the 4 pin connector, I have 4.8V until I press the power button, then it drops down to 0. 12V rail never turns on.
Only way to get 5V back is unplug/replugging the AC side of the PSU.
Tried powering it with an ATX PSU, console boots fine. I measure 1.7V between the 5V and GND pins on the 4pin connector, but ~5V between the 5V pin and the large ground traces on the board. Draw on the whole 5V rail never exceeded 900mA.
And that’s where my small electronic skills are struggling without a schematic, I’m not sure where to look next… If anyone has had similar issues and could help that would be great 
Else it’ll stay a frankenstein ATX powered thing