The Dell N870P power supply origins from the redundant PSU for the Dell Poweredge R710 / T610 rack servers. This post and video shows how to make it run standalone.
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The PCBs of this power supply is well documented with its silkscreen and modularly built with PFC front end, DC-DC converter and driver boards as extensions.
The backside of the main PCB reveals some specific areas of interest, for further analysis and hacking. Especially the OVP / Over Voltage Protection would be interesting.
The driver of the DC-DC output stage is a UCC3895. It is placed on its own extension board with 3 potentiometers for adjust output voltage and possible current limits.
Firstly I map out all the ground connected pins. Secondly I power up the power supply to look for standby voltages and housekeeping power supply rails. Thirdly I start out with a 100K resistor from ground to all unknown control pins, then move down to 10K and last 1K resistors to look for external power on signals. Repeat with +3.3, +5 or +12V auxiliary power supplies if nothing is found with the ground reference to input pins.
