Saturday, October 28, 2023

Oops on 1053 adjustment but fixed several others plus read another two boxes of 1620 cards for a different collector


In a previous post, I found a cam on the filter shaft whose position appeared to be seriously out of phase. During a print cycle, the machine rotates a cam which trips the escapement mechanism to move the carrier one column to the right. It must happen after the printing has completed, thus the timing of the cam is important. 

A filter shaft is geared to turn at the same time as the shaft for the carrier, both of which are turned by the main operational shaft when the print clutch has been tripped. The carrier shaft will lock the ball in its tilt and rotate position, swing it forward with appropriate velocity and return it. This shaft also lifts the ribbon so that it is in between the type ball and the paper on the platen. The filter shaft is used to release the keyboard on typewriters, as well as triggering the print escapement.

The challenge in following the maintenance documentation is the enormous variety in selectric mechanisms, even when it is a print only device like the 1053 on the IBM 1130 console. The 1053 is also used as part of the 1052 operator console for a S/360 mainframe, but its implementation is very different. Other 1053 are used as output log printers on mainframe systems, having their own implementations.

As one example of the variety of implementations, just considering the print only devices, consider the tab function. The 1053 on the IBM 1130 does have tab settings and a tab movement function, but the other print only 1053 such as the mainframe models do not include any tab oriented hardware. 

Because of this, the diagrams and procedures are not highly specific to the model you are repairing and as  a result mistakes are easy to make. I saw a 1053 document that showed the print escapement cam at the side of the machine on the far end of the filter shaft. I have a cam on the side and that is what I adjusted. 

Well, it turns out that the print escapement cam is inside, not as far along the filter shaft, while the cam I was adjusting provides a function that is not used on other selectric models. The outside cam is a lock which stops the shift mechanism from rotating the ball between upper case and lower case sides, during a print cycle. Thus the low point of the cam is when the interlock is in place, freezing the shift mechanism. On the print escapement cam, the low point of the cam is when it is not driving an escapement. 

Thus, at the time that a print cycle is not happening, the idle time, the escapement cam should be at its low point so as to not trigger movement, while the shift interlock cam should be at its high point to release the interlock permitting the operator to shift back and forth between UC and LC. I corrected the adjustment for shift interlock, undoing my error.


I also got the index (move down a line) and carrier return mechanisms to trigger properly. There are five functions that can be triggered, releasing a clutch on the operational shaft allowing motor power to drive the function. These are space, tab, carrier return, index and backspace. The 1130's console has three buttons on the front which can trigger the tab, space and CR functions.

In addition, five solenoids are implemented to trigger each of the five functions. The only way to move the paper up is to trigger index with the solenoid; similarly only the solenoid can trigger a backspace to move one column to the left of the current position. 

I verified that all of these solenoids are triggering the clutches to drive the function. I adjusted most of them to work properly. I am still fine tuning the backspace and the space functions while the remainder are in good shape already. 


Another collector had mailed two boxes of punched cards to me containing various historical programs for the IBM 1620 computer. It only took a fraction of an hour to unbox these and read all 4000 cards into separate files for each logical deck. 

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