Finding and fixing the space issue with 1052 console printer

RECAP OF FAILURE TO SPACE WITH AN XIO WRITE COMMAND

The typewriter is driven by an XIO Write to the console area code (00001) with the top 8 bits of the word signifying the request to the typewriter, either to type a character on the typeball or to execute a function such as carrier return. The controller logic fires one or more solenoids in the Selectric mechanism, then issues a response interrupt to signal that the operation is complete.

I was able to type all characters on the typeball and control all functions of the typewriter except for one. Requesting a space by XIO Write resulted in no action on the printer but a successful response interrupt from the controller. The physical Space button on the front of the typewriter successfully performs the spacing function, it only fails when XIO Write requests this. 

TOOK MEASUREMENTS TO FIND THE BREAKDOWN POINT

The scope demonstrated that all the circuitry in the 1130 was firing correctly when I sent an XIO Write to command a space. I then checked continuity to the solenoid pin inside the typewriter as well as appropriate resistance of the coil winding. This pointed squarely at mechanical issues inside the Selectric. 

I quickly discovered that the armature of the Space solenoid was gummed in place. It is located in a very difficult spot to reach for lubrication and checking, thus I missed it during the effort to free up every moving part. 

REPAIR AND RETEST

It didn't take much effort to free up the armature and allow the solenoid to trip the Space function on the operational cam assembly. I fired up the machine and indeed now the console printer spaces whenever the software requests it. 

LOADED CONSOLE DIAGNOSTIC INTO MEMORY AND RAN IT

I had captured the console diagnostics on the IBM 1130 simulator and produced a core memory load file so that I could get that code into the real 1130. With it loaded, I began executing the diagnostic. Its behavior depends on the setting of the Console/Keyboard toggle switch as well as the function(s) selected on the diagnostic. 

When I started it with the switches set appropriately, it ran through the series of printer tests. These require that tabs are set at column 20 from the left margin in order to work properly. The tests run include:

• Tab and Carrier Return tested
• Upper case characters
• Lower case characters
• Backspace and line feed
• End of line auto carrier return
• Registration (print, backspace and print)
• Lines are printed in black and red ink
• severe case (rock, roll and twist tests)

The printer passed with flying colors, almost perfect. I see a trace of stickiness when doing line feeds to advance the paper, plus sporadically the carrier return doesn't slam all the way to the left margin. I will attack the machinery with a bit more lubrication and exercise, but this typewriter is ready to have its cover and faceplate attached, resuming its rightful place under the display light panel and it front of the keyboard.