Additional Standard Power Connector
on PS/2 Mod. 50 and 70


WARNING: This is neither a joke nor is it intended for Beginners or Wanna-Bees.
All Tips given and all the described modifications are 'On Own Risk'
The Maintainer will give no warranty of any kind !

Read the entire article first, before you begin !

The Problem: Just installed an SCSI- or IDE-adapter in a PS/2 Mod. 50 or Mod. 70 and no power connector to which an SCSI- or IDE-drive could get connected to.

The Solution: Follow the instructions below and install one !

You need:
  • a soldering iron (a good one - not one for plumbers !)
  • a multimeter with VDC and Ohms-range
  • a standard power-connector (4 pins - maybe cut from a wrecked power supply)
  • a hot-glue pistol with some glue-sticks
  • some self-confidence (like always)

It is a good idea to leave the cables on the power connector as long as possible to make it fit on either direction a harddisk can be installed in a Model 50 or 70.

The power connector(s) looks like this from the frontside:
(I still love ASCII-graphics !)


             /------------\
             | o  o  o  o |
             +--++--------+
                ++       
               ^  ^  ^  ^
     12VDC ----+  |  |  +---- 5VDC
    (orange       |  |        (red
     cable)     GND  GND     cable)
             (black cables)     

    
  [Fig. 1a: Standard Power Connector]

12VDC-cable may either be orange or yellow


          ++-------++-------++
          |+-------++-------+|
          ++ ##  ##  ##  ## ++
           | ##  ##  ##  ## |
           +----------------+

             ^   ^    ^   ^
    12VDC ---+   |    |   +--- 5VDC
   (orange       |    |        (red
    cable)      GND  GND      cable)
             (black cables)


[Fig. 1b: 3.5"-Disk-Drive Power Connector]

12VDC-cable may either be orange or yellow
Now open your PS/2. Remove disk-drive(s) and harddisk (on Mod. 70). Remove the T-shaped disk-drive adapter and look at it from the rear (opposite side to where the disk-drives go in). On Model 50 it may still be fixed with a very thick and stable wire to the plastic subframe. Caution !

The Connector board looks like this:

+-----------------------------------------------------------------------+
|                      40  soldering pins                     40        |
|   oooooooooooooooooooo         |         oooooooooooooooooooo         |
|   oooooooooooooooooooo <-------+-------> oooooooooooooooooooo         |
|   1      2nd DD                          1       1st DD               |
|                                                                       |
|                            +--------------------------------------+   |
|         Mod. 70 HD ------->| #################################### |   |
|         Mod. 50 empty      +--------------------------------------+   |
+---------------------+                           +---------------------+
                      |                           |
                      |                           |
                      |                           |
                      |                           |
                      |                  |=|      |
                      |||||||||||||||||||| ||||||||
                      |||||||||||||||||||| ||||||||

                  [Fig. 2: Disk/Harddrive Connector Board]
What to do:
  • remove insulation at the 4 cables from the power connector
    (about 2 or 3 mm will do)
  • tin-lead them with soldering wire
  • solder them to one of the disk-drive connectors in the pattern from Fig. 3
    Solder them vertically in the same direction as the pin of the connector go.
    See also Warnings and recommendations further below.
  • check for continuity and the absence of short-circuits
    (Except: the two black wires are both connected to GND)
  • re-assemble everything
  • power the system on and leave the fingers on the power switch

  • if nothing unusual happens - you're almost through

  • if the system won't come up ... check everything again !

  • Finally: disassemble everything once more and
    use hot-glue to give the whole thing stability. 

                             +5VDC ----+  +--- +12VDC
                                       |  |
                                       V  V

                                       38 40
           Upper pin row .... O  O  O  O  O

           Lower pin-row .... O  O  O  O  O
                                       37 39

                                       ^  ^
                                       |  |
                               GND ----+  +--- GND

      [Fig. 3: Connections on the Disk-Drive Connector (solder side)]
Warnings and recommendations:
  • The maximum power drawn from this power connector is about 1 Ampere for 5VDC and 12VDC
  • 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.
  • On the connector for Drive 2 are some tiny connections on the board.
    Take care not to damage them while soldering the wires.
  • Remind, that the Mod. 50 / Mod. 70 power-supplies aren't that powerful at all.
    Especially the Mod. 50 power-supply 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.
Feel free to report experiences.

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© 1997 by Peter H. Wendt / pw-software production