8550/70 756x Power

Add Power Connector

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

7561/62 PSU P/N 33F5202 FRU 57F2728
  Made by Plessey in Italy.... 
Input 95-120v @ 3.6A 50-60Hz, 200-240v @ 1.9A 50-60Hz
Output (dc):
 +5v  25.6A
+12v  3.3A
-12v  1A
Battery Charger 26v dc @ 40mA

  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 PSU
   Made by ASTEC, Model AA15530, IBM PN 90X9409, FRU 90X8626. Max continuous output power is 132 watts for the 8570 PSU.

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                 ---

8550/Z PSU
Rich keeps me honest 
   The original one coming with Mod 50.50z was rated 94 watts, no fan. HMM says part number is [90x9366]. (Ed. He's right, I remember the fan assembly that slides in at the back of the case. Old age, I guess...) 

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. 

Remove the Power Supply
   Remove the two screws at the back of the case. Remove the screw at the front inner corner. Pull PS out from planar. 

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 

8570 / 8550 Bus Riser Power Hack FRU 90X1111
 Original HERE

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.

   Please note that clone PC power cables use yellow/black/red, while IBM systems use yellow/black, or red/black/blue. What is important is the position of the conductor. Note that the drive power connector is keyed with bevelled edges.

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. 

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