Using the EMR II keyboard

daneli

05 May 2022, 19:22

This is my first post here. I picked up an unused IBM EMR II keyboard some time ago. I decided to finally give it a try. The shielded cable has thicker internal wiring and a D-sub connector on the end. While I was puzzling over how to build an adapter for this cable, it occurred to me that it might be possible to use an original XT cable with this keyboard's controller. In fact, it turns out that if you remove some of the magic epoxy/plaster/paper mache that shields the internal controller board, you discover a standard XT style internal keyboard connector. You can remove the shielded cable and then connect a standard XT cable to the controller. The XT cable functions fine when connected to the EMR controller.

A couple peculiarities:

My example, as noted on the Deskthority wiki page, has "Caps Lock located to the left of A, Ctrl located to the left of the spacebar, and Alt to the right of the spacebar." However, the scan codes generated by pressing these three keys do not correspond to what the key caps indicate, instead they are identical to what you would see if you pressed keys in these positions on a standard XT keyboard. So, if you press the key to the right of the spacebar you get Caps Lock, just as you would on a standard XT keyboard, even though that key on the EMR board has an "Alt" printed on it. Same thing for the Ctrl and Alt keys. In effect, the key caps for Ctrl, Alt and Caps Lock are all in the "wrong" place. (I assume that whatever system these keyboards were originally connected to was doing its own key reassignments for these 3 keys.) It is an easy problem to fix - if you see it as a problem - by moving the Alt key to the left of the spacebar, just as it is on a standard XT. However, you cannot just swap the Ctrl key into its original XT position because the EMR Ctrl key is too wide to fit to the left of A. I fixed this problem by swapping in a standard XT Ctrl key.

Also, the bracket key "}]" closest to Enter on the EMR keyboard is not slightly oversized as it is on a standard XT keyboard. That leaves a bit more space around that key on the EMR board - you can see more of the plate underneath than you can on a standard XT keyboard.

The D-sub connector on the EMR II cable has some identifying information printed on it. "Kern Eng. 50619." It turns out Kern Engineering is still in business. Their web page says their "components have been and are being used throughout the world to protect sophisticated electronic hardware and systems under the most adverse conditions against EMI/RFI and EMP."

Even though I've made it less likely to survive an EMP, it is great fun to give a keyboard manufactured in 1987 an inaugural voyage. The typing experience is fantastic and feels to me to be indistinguishable from that of a standard XT keyboard.

daneli

31 May 2022, 02:08

D-Sub to Din-5 Adapter

The keyboard cable on the EMR II employs a D-Sub connector with a heavily shielded backshell to connect to the serial keyboard port on the back of the Tempest version of the PC XT computer. Only 4 pins of this serial connector are used. At the controller end of the keyboard cable - inside the keyboard case - the cable is wrapped in what appears to be braided stainless steel shielding. There is continuity between this braided shielding and the D-Sub metal backshell at the other end of the cable.

In order to use the EMR II keyboard we need a D-Sub female to 5-pin male DIN-5 adapter. Like this:

Image

This adapter will allow the EMR II to connect to a Hagstrom XT to USB converter, a Sorarer's converter, or the like.

To make this adapter I ordered a standard D-Sub female connector with a metal backshell and an IBM-style keyboard extension cable from DataPro:
https://www.datapro.net/products/ibm-pc ... 5-m-m.html

I cut the keyboard extension cable so there were a few inches of wire behind the male Din 5 connector. I stripped these wires and used a continuity tester to determine the colors for each of the five wires connected to the five Din pins. (There was a bare sixth wire - uninsulated - that connects to the round metal ring of the Din-5 connector.)

Here's a simple visual representation of the D-sub female connector - solder side, with the solder cups facing you:

1   2   3   4   5
 6  7  8  9


And here is the Din-5 connector - with the pins facing you and the wires exiting from the back of the pins you are facing:

   --
A    E
 B  D
  C


Using the numbers and letters above as a reference, here's how to solder the wires from the Din-5 cable to the female D-sub connector:

  Wire for Din-5 Pin   Connects to   D-sub female solder cup in position

     C         ->           2
     A         ->           3
     B         ->           5
     D         ->           6

I pinched the bare uninsulated wire from the keyboard extension cable against the metal shell when I closed up the backshell. (The effect of this is that when the adapter is connected, there will be continuity between the braided stainless metal shield at the controller end of the cable all the way down to the outer ring of the Din-5 male connector at the other end.)

With this adapter in place, the EMR II keyboard functions exactly like a normal XT keyboard. There do not appear to be any differences between the EMR II keyboard controller and a normal XT controller.

User avatar
JP!

31 May 2022, 14:25

Thanks a lot for the details! I assumed the controller was the same but didn't want to remove the coating on the controller of my XT. 8-)

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