8580 Power Connector Pinout
Repair of PS/2 Model 8580 Power Supply  (to Al Savage)

-Lead +Lead Vdc Min Vdc Max
  2     9    -9.0    -15.0
  2     3    +9.0    +15.0
  2     1    +3.7    + 6.2

Wire Color Codes

This is pretty simple :-)
      GND
       |
+12VDC | -12VDC
    |  |  |
    |  |  |  +------------- Power Good
    V  V  V  V
    3  6  9  12 15
  +----------------+
  ||o  o  o  o  o  |<------ HD-LED (GND=off)
2 | o  o  o  o  o| | 14 <-- all GND (black)
  ||o  o  o  o  o  |<------ all +5VDC (red)
  +----------------+
    1  4  7  10 13

>(BTW, one thing worries me about my 8580's power supply - it crackles. When the machine is switched _off_ there is a quiet crackling sound from  the back of the power supply, it sounds like it could be in tune with the 50Hz mains frequency.  When I first heard it I nearly took the
machine back for a refund, but it doesn't seem to have any effect.)

Half the PSUs on the Mod. 80 failed with broken power switches. The red ones more often than the white ones. The same switch has been used in IBM 327x Terminals (and 525x ones) and is known for high failure rates. It was available as spare part.

Are you sure the noise comes from the rear ? The "switch cover" in the front acts like a "echo chamber" and reflects the crackling from the switch to the rear.
On the other hand: it might be an isolation failure on the AC Line filter as well. Or on one of the capacitors of that filter. Had that too. You will have to open the PSU for a failure diagnosis ... and you should *know* what you are doing in this case. It is dangerous to fiddle with the inards of switched power supplies.

Something I forgot: One of my 95s made "crackling noises" too. The clue: replace the power cord. The one I used seemed to have too loose contacts. After I used a different one the crackling went away ...