Add Power Connector

Power Supply Pinout
   Same for 8550 (94w), 8570 (132w) and 756x (180W). 

  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 Health
   The way these 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 

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.