Hard disk interface connector

   Col 1                Col2                Col3
1  +12V Ret (power/2)   +12V Ret            +12V Ret
2  +12V (Power/1)       +12V Ret            +12V Ret
3  +12V                 +12V                +12V
4  Gnd                  RWC (J1/2)          Gnd
5  Gnd                  HS2 (J1/4)          Gnd
6  Gnd                  Write Gate (J1/6)   Gnd
7  Gnd                  Seek Comp (J1/8)    Gnd
8  Gnd                  Track 0 (J1/10)     Gnd
9  Gnd                  Wr Fault (J1/12)    Gnd
10 Gnd                  HS0 (J1/14)         Gnd
11 Gnd                  Spare (J1/16)       Gnd
12 Gnd                  HS1 (J1/18)         Gnd
13 Gnd                  Index (J1/20)       Gnd
14 Gnd                  Ready (J1/22)       Gnd
15 Gnd                  Step (J1/24)        Gnd
16 Gnd                  DS0 (J1/26)         Gnd
17 Gnd                  DS1 (J1/28)         Gnd
18 Gnd                  DS2 (J1/30)         Gnd
19 Gnd                  DS3 (J1/32)         Gnd
20 Gnd                  Direction (J1/34)   Gnd
21 +5V (Power/4)        +5V                 +5V
22 Drive Chassis        Drive Chassis       Drive Chassis
23 Selected (J2/1)      Gnd                 Gnd
24 N/C                  Gnd                 Gnd
25 N/C                  Gnd                 Gnd
26 N/C                  Gnd                 Gnd
27 N/C                  N/C                 Gnd
28 Gnd                  Gnd                 Gnd
29 WrData+ (J2/13)      WrData- (J2/14)     Gnd
30 Gnd                  Gnd                 Gnd
31 RdData+ (J2/17)      RdData- (J2/18)     Gnd
32 Gnd                  Gnd                 Gnd

Grounded : Power/3, J1/1-33 (Odd #), J2/2,4,6,8,11,12,15,16,19,20

J1 - 34 pin control cable, J2 20 pin data cable.

Col 1 is leftmost, looking at pins on backplane plug. Row 1 is at the
top of the machine.