Designed SMS socket and having it manufactured

THE NEED FOR AN SMS SOCKET

The Standard Modular System was the construction methodology used for IBM computers in the generation from the Stretch computer until it was replaced in 1964 by Solid Logic Technology of the System 360 and 1130 systems. The 1401 and the 7094 are two well known systems based on SMS. 

IBM did use SMS components during the later generations such as S/360, both for components such as power supplies and for attaching older peripherals originally designed to connect to SMS machines. In the IBM 1130, many peripherals are attached using SMS paddle cards and SMS power cards. 

The paddle card looks like the end of an SMS logic card, but is attached to cables. SMS cards have 13 pads, labeled A through R (as they skip the letters I and O due to their resemblance to the digits 0 and 1). The power card is similar but has some pads combined into fatter pads to handle more current, e.g. M and N become a double width pad, and it has a notch in the middle. The connector block into which power cards are plugged has a steel bar to block ordinary SMS paddle cards but allow the notch of the power card to slide around it. 

I do not have any reasonable source for SMS paddle cards, SMS sockets, nor the gender changer/adapters that allow two paddle cards to be connected. I had to build my own small PCBs to work as SMS paddle cards and SMS power cards. 

The challenge I face is that there is another option connected to a cable, a socket into which a paddle card will plug. One of the cables coming from the 1053 Console Printer, a selectric typewriter used as the console of the IBM 1130, has a socket on it rather than a paddle card. My 1053 Emulator project was originally built with SMS paddle cards, but one of the cables either needs a gender changer/adapter or a socket.

CONCEPT FOR SMS SOCKET

I realized that I could solder some RF shield fingers onto the pads of one of my SMS paddle PCBs. These are springy gold plated contacts that stand 2.5 mm above the PCB but can compress down to 1.5 mm or less, ensuring a good contact across all thirteen pads of whatever we mate to. I needed a body that would hold the paddle card PCB with its fingers and hold an inserted SMS paddle card against the contacts. 

At first I was working on a design that would put my paddle card PCB inside and have a slot for the insertion of an SMS paddle card. However, I realized that the paddle card PCB itself acts as one side of the socket, thus it does not need to be enclosed. 

I designed a part that will be installed over the top of my paddle card PCB, bolted in place through the four holes I put into that PCB. The opening of that part is 3.8mm high, thus an SMS paddle card at 1.54mm will slide in and compress the fingers on my PCB down to 2.26mm height, giving a good solid contact. The part has a wall to stop the SMS paddle card from sliding in too far. 

It has two additional features, notches for mounting and an opening for the cable wiring to exit the socket. The opening is not particularly important, but the notches are key to use in the 1130.

The IBM 1130 has a U shaped bit of metal, the height of the U much larger than the width of the opening. The opening itself is just over 56 mm. The U shaped bit is rotated 90 degrees and mounted in the 1130. 

The IBM gender changer/adapter parts have notches built in so that they can be slid into the U and thus anchored, with SMS paddle cards plugging into the front and back of the adapter. SMS sockets such as the one attached to the 1053 also have the notches and are slid into the U the same way. 

DESIGNED IN FREECAD AND SENT OUT TO MANUFACTURE IN NYLON

I whipped up a design for the body that converts my SMS paddle card PCB into a socket.

I transmitted the design through Cloudcraft and should have three of them by the end of next week.