Verified correct typing of all 88 characters on the type ball of the 1053; design decisions and study for the FPGA box rebuild

QUICK AND DIRTY METHOD TO TRIGGER ALL VALID CODES TO THE 1053

I set up my new power supply to output 48V and fed it to the typewriter through its power SMS paddle card. The solenoids get grounded by the CPU to complete the circuit and activate a function. I had a spare SMS card socket which I wired to a breadboard. 

Setup to select characters on 1053 typewriter

By plugging in jumpers between the seven solenoids and a common strip, I can briefly connect that strip to ground to type a selected character. I had prepared a comprehensive table of all the characters on the typeball, which involves selected one of four tilt levels and a rotation from +5 to -5 positions including 0 (home) in the center. 

This gives 44 selectable characters on the hemisphere. If you 'shift' the machine it rotates the typeball 180 degrees, exposing the other side for a second set of 44 selectable characters. The combination of shift, tilt and rotate chooses any of the 88 characters on the typeball. 

SPOTTED SECOND SPRING IN CARRIER BUT TAB STILL NONFUNCTIONAL

Armed with the pictures from the typewriter repair videos I watched, I was able to spot the small second spring sitting in the escapement area of the carrier. The typewriter has a rack with teeth that defines the character positions across a line. Pawls engage with the rack to hold the carrier in place during normal operation. 

Other pawls force the carrier in reverse for backspace operations, or click over to the next tooth on the right for space operations. A latch should hold the pawls away for a tab operation, being reset when the little pin is set in a position for a tab stop, by forcing the mechanism back to release the tab latch.

My issue is that the tab is not latching and I can see a lever flopping around down deep in that section. It should be connected to the small spring, but perhaps the far end is loose. Visibility is quite limited so that I still don't know exactly what is wrong. 

This lack of latching also causes some problems sporadically for both carrier return and normal spacing, where the carrier sticks or rubs because of that loose latch. This can jam the carrier at a specific position and block spacing, or more commonly it causes drag that almost stops the carrier from returning. 

SOME FUNCTIONS WORK WELL UNDER SOLENOID COMMAND

The Space, Line Feed and Backspace solenoids were activated under power and worked just as expected. This confirms the mechanisms are set up properly as they do as intended both under power and with manual hand cycling. 

Shifting between 'upper' and 'lower' case hemispheres of the typeball works great under power. Similarly, shift to Black and shift to Red work under power. I did notice that the ribbon lift mechanism needs a bit of adjustment as it isn't solidly in the red portion of the ribbon when shifted that way. This is a simple adjustment I can do later. 

FAILING FUNCTIONS

On the other hand, the Tab solenoid does absolutely nothing. I expected this as I had found that I couldn't trip it manually by pulling on the linkage from the solenoid. Whether this is related to the other tab problems or a separate fault is yet to be determined. 

The other function that doesn't work well as CR-LF, a combination of carrier return and line feed, as the sticking tab latch makes the carrier drag along the escapement rack instead of zipping to the left. Under manual cycling it works just fine, but not under power.

CASE SELECTED FOR THE REBUILT 1130 EXTENDER BOX

I found a case that was reclaimed from some RF gear and seems ideal for my purposes. It doesn't look like a PC and is not very strongly tied to a particular period of time. It is ordered and my design is underway to fit inside that shape.

DESIGN DECISIONS MADE

I will create one large PCB to implement all the logic spread across multiple boards and discrete components in the current unsatisfactory implementation. The existing box has four small PCBs that hold 12 receiver circuits each, for signals coming in from the 1130 CPU. It has two perf boards with seven driver chips to send 42 signals outbound to the 1130. There is a FPGA board that was cabeled to all of this. A PC power supply gives us 3.3V and 5V, then a regulator circuit produces 3V for the SLT logic levels. Finally there were several cables entering the box. 

The old method required cabling between all the boards, a mess of wiring inside. The boards weren't mounted solidly, instead they were separated by chunks of foam. Having a single board will slash the amount of wiring. It can be firmly mounted with standoffs and screws to the case. 

The mess that is the old implementation

The case will fit a micro-ATX size PC power supply, which I will plug into the board I am designing. That board will have the relay to switch on the power supply when the 1130 starts up, also the 3V regulator and connectors to drive the four LEDs that come on the case, with some status that makes sense as I finalize the design.

Closeup of the 160 pin signal connector

The wires from the 160 pin signal connector will attach to screw terminals on my PCB. The FPGA will mount on header strips installed on my PCB. In addition to the connector carrying signals to the 1130, there are additional signals on a second cable I created to expand this beyond the IBM Storage Access Channel function. That expansion adds interrupt levels 0 and 1 as well as the Program Load sequencer trigger signal. 

There are two SPI links implemented on the FPGA which can connect to expansion hardware to drive real peripherals such as paper tape and plotter devices. I will provide connectors for them on the PCB. Finally, I will provide a header strip for all the unused signal pins on the FPGA to support any future features I want to add. 

The FPGA has a mini USB connector that provides the USB Serial link to the PC that provides the graphical interface and stores the files connected to the virtual peripherals. Rather than feeding a cable through a hole, I will find an extender to provide a USB connector on the outside of the case. 

VHDL CODE CLEANUP FOR THE FPGA

I am working through the FPGA code to clean up minor issues, but I don't want to touch anything that is functional until I have the rebuilt system working exactly like the old one. 

ADDED WASHER TO REDUCE PICKER PLAY ON THE DOCUMATION M600 CARD READER

My M600 reader had a picker arm which had excessive play vertically, allowing the picker foot to jump up and down. This caused scoring of the aluminum under the foot, forced a wider gap that lessened the vacuum applied to pick cards, and led to more misfeeds compared to the properly adjusted M1000 reader. 

I measured carefully, bought a washer to add the necessary thickness, and reassembled it. The arm will now move more normally. Once I reassemble everything, I hope to adjust it to deliver solid reliable reading for years to come. 

Washer in place, snap ring reinstalled.