This PSU has an external, two pin Molex connector that provides power to the case fan. There is a 9.25"Wx1.75"H inch hinged cover on the lower outer side of the psu. It is fastened at the front by a single captive standard screw. The cover pivots open on the rear hinges, revealing a three pin Molex power connector, like a female drive power connector. The battery cavity is 1.875" deep.

8570 Voltage per Pin
Voltage (DC V)        Pin #           Current/Pin (mA)
-12                     1                  300
+12                 3,5,7,9,11,13          535
 +5                 15-47 Odd #s only     1130
DC Return           2-48 Even #s only      915
System Status           49                 ---
Pwr Good                50                 ---

MODEL NO.:  AA13621 IBM  P/N:    90X9527 IBM FRU P/N: 90x9366 

VOLTAGE           PIN NO.          CURRENT/PIN (mA)
-12V                1                 410
+12V            3,5,7,9,11,13         350
+5V             15-47 ODD NO. ONLY    760
DC RTN          2-48 EVEN NO. ONLY    640
SYSTEM STATUS       49                ---
POWER GOOD          50                ---

Max continuous output power is 94 W. 

   This is from a 50Z.  No side blower.  (The blower plugs into the motherboard, is supported by two plastic snaps to top rack, and it blows out the rear of the 50/50z unit). CASE BOTTOM of power supply does not have a screen, it has finely punched holes, 11 or 10 holes across, the length of power supply. 
     Cases vary color, gold/silver.  Security torx, 5 on side 2 on top. Like unto Mod 70 supplys, except no side blower, and lower rating. 

Power Supply Cleaning
8550 / 50z
   The way the 50 / 50z PSUs were built, they have a screen across the bottom side. Just like on a clothes dryer, you have to remove "lint" from the screen. I used a T-10 security Torx to open it.The fan is a Panaflow DC Brushless, Model FBH-09A12L, 12v 0.14A or a Nidec Beta SL Model D09B-12PLL 12v .09A 

8570
   These have the built-in fan. Use a T-10 to open.

JN1 Floppy 1 (A:) JN2 Floppy 2 (B:)    The three resistor/capacitor pairs on the riser are for DC-buffering and decoupling. The earlier risers lacked them and once you'd stuffed in 2 FDDs or 1 FDD and a tape problems occured with loss of data during copying and suchlike.

From Peter Wendt 
Warnings and recommendations:
    The maximum power from this hack is about 5v/1A and 12v/1A so if you have both disk-drives or one disk-drive and a tape-streamer installed ... it is  probably not a good idea anyway. It will -non the less- work in most cases, until the unit driven over this port doesn't take too much power. Most modern Harddisks will not exceed these limits. In case of doubt: consult drive manual for its power-consumption. Or don't do the modification. 
    If you have only one disk-drive installed, take the connector of the second drive for modification. Caution!!  Take care not to damage the tiny connections on the board near the connector for Drive 2 while soldering the wires. 
  Remember, that the Mod. 50 / Mod. 70 power-supplies aren't that powerful at all. Especially the Mod. 50 power-supply (94W!!!) is known to have lesser power than assumed. If you'd already installed a -386/-486 upgrade, 64Megs of RAM, SCSI-adapter and a Hi-Resolution graphic board it will surely collapse.