This power supply is from an HP Z230 Small Form Factor PC. It is a proprietary power supply. It has only three connectors. P1 and P2 are proprietary and P3 is identical to the ATX/BTX 4 pin +12V power connector that supplies CPU power, except that the yellow wires are instead brown on this power supply. All P3 wires are 18 AWG. All three connectors plug onto the motherboard. The motherboard has a header with a harness that terminates in SATA power connectors for drives. P1 is the main power supply connector for the motherboard. Circuitry on the motherboard then generates +5V and maybe +3.3V for SATA drives. Below are the pinouts for the P1 and P2 connectors. See the page https://pinouts.ru/Power/atx12v_pinout.shtml for the pinout of P3.
P1 Connector Pinout
|3||-12V||Blue||Blue wire, -12VDC Supply||24 AWG|
|4||+12V||Yellow||Yellow wire, +12VDC Supply||18 AWG|
|5||+12V||Yellow||Yellow wire, +12VDC Supply||18 AWG|
|6||+12V SB||Purple||+12V Standby||24 AWG|
The P2 Connector is a single row 0.1" spacing female connector with tabs so it can be only connected in one orientation. The pins are numbered left to right, with the tabs up.
P2 Connector Pinout. Note that the connection directions noted below are with respect to the power supply.
|1||COM||Black||Ground or N/C||24 AWG|
|3||Power Good||Grey||Approximately +3V when power on with no motherboard connected.||24 AWG|
|4||/Power_On||Green||Short to ground to turn power supply on||24 AWG|
|5||TAC||White||Label inside power supply. Fan tachometer output.||24 AWG|
|6||FANCMD||White w/ red stripe||Fan PWM Control input.||24 AWG|
The signals and descriptions above were obtained through direct measurement of voltages from the power supply or via board labels inside the power supply. The fan connections were confirmed via https://pinoutguide.com/Motherboard/mb_pwm_fan_pinout.shtml and viewing the power supply board and labels thereon.
Ground on pin 1 in P2 is not always present and sometimes not needed. It is noticed for P2 that the first pin not connected, not the second green on ground = start of the power supply fan