Finalizing work on SSM 1053 console typewriter

SYSTEM SOURCE MUSEUM CONSOLE PRINTER BROKE A ROTATE TAPE

During the VCF East event, the rotate tape of the console printer on the recently restored System Source Museum 1130 broke , while it was being exhibited there. I brought just the typewriter back with me in order to change the tape and make sure it was in perfect condition before returning to Baltimore.

FINE TUNED ADJUSTMENT FOR ROTATE TIMING

With the new tape in place, I carefully examined and tweaked the timing of the machine to ensure that the tapes are not subjected to any extra stress. During a print cycle, the mechanism first pivots levers to pull or release pressure on the rotate and tilt tapes, positioning the typewriter ball at the proper character. Next, the mechanism pivots locking (detent) bars to lock the type ball in its exact position before it strikes the paper. The ball is flung forward to strike the paper.

After hitting the paper the locking bars get released so that the rotate and tilt tapes can return to their idle positions; meanwhile, the type ball continues its returns to wait for the next print cycle. The timing of the locking bars and the rotate/tilt tape movement have to be synchronized. If the tapes change pressure while the ball is locked, it adds stress to the tapes; if the tapes have not finished moving yet, the ball can be locked on the wrong character in addition to putting strain on the tapes. 

A print cycle involves a 180 degree rotation of the cam shaft,  driven by the main motor when released by the print clutch. This cam shaft directly turns cams that pull down levers to select and drive two metal tapes. Those tapes move on a pulley system and run to the print carrier where they tilt and rotate the ball. The motor is continually turning the right side of the shaft, called the operational shaft, but the clutch keeps the left side, the cam shaft, from turning except when the clutch engages for one cycle. 

The cam shaft is also connected via a gear train to a print shaft that the print carrier slides along. This print shaft has a slot along its length that turns mechanisms in the carrier. The rotation of the print shaft inside the carrier moves the type element forward to print a character, but also engages the detent lock to hold the ball in position for the strike and does other actions such as advance the ribbon. 

The relative timing of these two shafts is adjusted by loosening setscrews in the gear on the end of the print shaft, then moving the print shaft to the point it needs to be relative to the position of the cam shaft. Any movement of the pivot levers that are rotating and/or tilting the type ball must have ceased before the detent is engaged. This holds the ball until after it has struck the ribbon to impress a character on the paper. 

The detent should be released before the pivot levers start to return to their idle conditions, turning and tilting the ball to its home position. The time when the detent is engaged must be aligned very well with the print selection done by the cam shaft which is ultimately swinging the rotate and tilt pivot arms. 

I hand cycled printing while adjusting the timing of the locking bar and print ball movements. I wanted the locking to start AFTER the ball reached its final position and to be released BEFORE the tapes start releasing. If that works properly then the tapes will last a long time. 

I had found that the IBM documented procedure for setting the relative timing did not directly look at the detent lever movements nor the pivot arm movements, instead dealing with secondary indications that I believe are less reliable in achieving the correct operation. 

I will try a few under power later, perhaps, filming in slow motion, but as far as I can tell with very careful hand cycling, the timing of the detent lever latching and the rotate and tilt tape movements are perfectly synchronized. 

NEW ACRYLIC LID FOR PRINTER BEING BUILT

I designed a thick lid for the 1053 typewriter cover as the SSM machine did not have its original IBM part. I will have to glue a couple of small blocks to the underside that will engage the springy metal on the cover that holds the lid in place. This is not an exact copy of the IBM lid, since that has curves and bent sections that would be very challenging to duplicate, but it provides the same function and will look very similar to the casual observer. 

POWER CONNECTION SMS PADDLE CARD REPAIRED

During the removal of the typewriter at VCF, I noticed that the SMS paddle card which connects the 1053 to the power block of the 1130 system had sustained a crack. This broke the metal traces between the card fingers and the spot where the wires were soldered down. 

After an epoxy repair of the card itself, I added some bridge wires to restore connectivity across the line of the crack. The card delivers 115VAC for the motor, +48V for the solenoids, the system ground connection and frame ground that protects users touching the case. Thus the card can now be plugged in and used successfully. 

REINSTALLATION INSTRUCTIONS TO BE PREPARED

I am typing up some instructions for reinstalling the console printer onto the 1130 system. The main difficulties surround the insertion of the cables into the 1130 since the SMS connectors for power and signal lines are buried down inside the machine and can be confusing to a skilled technician who is not totally familiar with IBM systems of that era. I will use lots of pictures to make it easier for the staff that has to put this back on their machine.