Thursday, June 16, 2022

Will begin debugging of the console printer device controller, although the typewriter not yet working


A few years ago I built an Arduino based box that would plug into the IBM 1130 in place of the 1053 Console Printer, which is an I/O Selectric sans keyboard. The connection is by way of three SMS paddle cards - these plug into SMS connectors to deliver signals and power for the console printer.

SMS - Standard Modular System - is the predecessor to the 1130's SLT. It is a technology and packaging standard used to create machines such as the 7094 and 1401 computers. IBM replaced SMS with Solid Logic Technology to build the next generation, systems such as 360 and 1130. It was a technology using printed circuit cards with 13 fingers on the end that hosted discrete transistors, resistors and other components. 

IBM was known for reusing designs and products from earlier generations rather than redesigning everything for each new generation. Thus, the 360 and 1130 systems used the 1403 Line Printer that was SMS based and originally designed for the 1401 computer system. IBM used the 1402 Card Reader/Punch, with some enhancements, as the 2540 for the 360 generation. 

They used the I/O Selectric from the 1050 Communications system, SMS based, as the console printers on both 360 and 1130. Also from that older system, the 1055 Paper Tape Punch was used with the 1130. A different borrowed mechanism was used as the 1134 Paper Tape Reader. These all used SMS connections.

They used the 029 Keypunch keyboard as the console for both 360 and 1130. The printing mechanism from the 407 Accounting Machine, pre-SMS, was used as the 1132 Line Printer for the 1130 system. The plotter from the 1620 computer was reused as the 

Every SMS based system that was reused came with connectors and some controller logic that was implemented in SMS. IBM's solution was to hide the SMS connectors inside the 1130. With S/360, IBM built an interface box called the 2821 that had sections of SMS logic married to SLT logic in different gates which communicated with 360 channels. The IBM 1130 had the 1133 Multiplexor unit that did similar things, with gates of SMS controller logic for the 1403 printer married to SLT that communicated with the Storage Access Channel (SAC) feature of the 1130. 

In the case of the 1053, all the controller logic was SLT based inside the 1130, but the connectors to the typewriter were SMS based. The solenoids on the 1053 ran at 48V and the microswitches were powered by 12V, just like the pushbuttons of the 1130. One SMS paddle card plugged into the SMS power socket group, providing the 115V for the typewriter motor, 48V and 12v, plus ground. Two paddle cards plugged into the signals group of SMS sockets just above the power group. 

The feedback from the machine was through a variety of microswitches that informed the controller logic of when the Selectric mechanism reached some point in its operating cycle, for which relay boards controlled by Arduino worked nicely. The 1130 device controller had open collector drivers that would ground a particular solenoid line to activate it, allowing the 48V to flow through the driver to ground. I used relays driven by the Arduino for this purpose, pulling the input pins to ground from their weak pullup 5V state. 

I programmed a sketch to emulate the machine, providing suitable timing for the feedback signals based on when a print or other cycle was triggered by solenoid. I read the activated solenoids, translated them into ASCII characters, and sent those out the serial link. Thus, a terminal program on the remote end of the USB cable would see what was being typed exactly as it would have appeared on a real 1053.

I emulated the tabs, with Tab Set and Tab Clear buttons on the box. It tracked where the virtual typeball was sitting along the carriage and advanced by emitting spaces to the next remembered tab whenever a tab was requested. My box showed the column number of the carrier on a display on the front. It also provided the three buttons for directly triggering 1053 functions of Space, Carrier Return and Tab.

The Console Printer emulator

The terminal emulator used to connect to this should support UTF-8 and ANSI Colors, thus it will display the logical not and cent sign characters properly and show the selected black or red ribbon color for each typed character. 


Selectric mechanisms were lubricated with grease and oils that dry up, binding dust from the air, making a sticky goo which inhibits proper operation of the mechanism. This all has to be cleared out and the machine properly lubricated with modern materials. 

A selectric typewriter has two metal ribbons that cause rotation and tilting of the typeball, but let the carrier move left and right along the carriageway. These move over pulleys on each side and levers move the pulleys in and out to cause the rotation or tilting. One of the ribbons has been broken, which is common when the machines are stuck due to gumming but someone tries to move the carrier. 

Also, there is a plastic ribbon that moves the ribbon lift mechanism lever so that the letter is typed through either the top or the bottom half of the ribbon. Using ribbons that have both red and black sections, this allows the programmer to select either color for typing characters. This ribbon is also snapped. 

Finally, the connector to the paper sensing microswitch near the rear inside of the cover is disconnected. This feeds the Forms warning circuit that illuminates a Forms lamp on the 1130 console and causes the device controller to consider the typewriter Not Ready. It must be connected to use the real 1053 when it is restored and ready for operation. 

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