1053 Console Printer has capacitor replaced - motor now working well - one small issue to debug

MOTOR NOW RUNS AT FULL STRENGTH

With a proper value capacitor wired correctly to the motor, it now starts up crisply and can maintain torque through the printing and movement operations of the 1053. The results were all I hoped for, with clean typing, tabbing, carrier returns and other operations. 

The replacement was close enough to the original equipment part used by IBM that it fits into the existing bracket and available space. 

RAN HAND LOOP TO SEND COMMANDS - DISCOVERED INTERRUPT NOT RAISED

If I reset the 1130, which sets the initial state of all the flipflops in the machine to their starting state, I can fire off one command to the typewriter, which it performs well but only that one will be accepted. The typewriter controller logic should raise interrupt level 4, presenting an operation complete status in the DSW, but it did not occur. 

The logic for a print cycle which culminates in the interrupt request looks at a signal from the typewriter (-Twr CB Response) to tell it that the machinery has completed its movement. It won't accept a new command until the prior one is over, to avoid jamming the machinery with conflicting movements of parts that might occur from overlapping operations. 

The -Twr CB Response signal is a series of three microswitches that are normally closed, delivering +48V to the controller logic. When the typewriter is in motion during operations, one of these is opened for the portion of the motion that can't be interrupted by new requests. The logic looks for the -Twr CB Response signal to drop from 48V to 0, then return to 48V as the operation is completed. 

I did a very quick check as I was preparing to leave the shop for the day, testing continuity from the pin where -Twr CB Response enters the logic compartment going back to one of the three microswitches. It should have shown continuity, but there was no connection registered by the ohmmeter. 

I expect this to be a relatively simple issue to find and fix, when I return to the shop tomorrow. One of the three microswitches is right next to the capacitor mounting position, thus I might have disturbed something during my work. 

REMAINING ISSUES TO BE RESOLVED - SPACE AND FRONT PANEL BUTTONS

The front panel buttons - Space, Tab and Return - fire the same operational unit clutches as the solenoids when an XIO instruction requests those movements. Therefore, since the XIO versions work properly, the failure is due to mechanical adjustment of the buttons and their linkages. I will address this later as it is not essential to running the disk diagnostics. Below is some background on how the adjustments are made. 

The adjustments for these take place in two places and they interact. There is no process I can see other than trial and error to work out the best adjustment for each half of the mechanism. 

A pivot on a bar fixed to the typewriter frame pulls on a cable - similar to the cables used to open automobile trunks or to adjust lawn mower carburetors - that sides inside a metal sheath. The other end of the cable is attached to a swing arm, spring loaded to its idle position, that will push down to trip the operational clutch release latch arm to trigger the desired function such as tab or carrier return. 

I can adjust the positions of the cable, the swing arm, the pivot and by tweaking all, I get a positive release of the operational clutch release latch for a clean movement of the pivot at the front of the typewriter frame. 

The faceplate of the console printer has the sixteen console entry switches attached to the top, some lever parts involved in setting and clearing tab stops, a display window that shows the left margin, current carrier column and right margin, and three rectangular pushbuttons marked Space, Tab and Return. 

These three buttons are spring loaded to remain toward the front, with a foot on the rear of each button that will push on the pivot arm for the other mechanism. The front of the pivot arm has a screw whose head is contacted by the foot on the button. By turning the screw in or out, I can adjust the position of the pivot at rest and when the button is depressed. 

The position of the button foot when it is unpressed, held out by the spring loading, isn't easy to see when the faceplate is installed on the front of the typewriter. This makes it challenging to set the screw on the pivot arm to a reasonable position that just touches the button at idle and also pulls the cable far enough to reliably trip the operational clutch release when the button is depressed. 

Adding to the challenge, if the cable pulls on the swing arm too far, it can slide under the operational clutch release latch and get stuck in place, blocking both the operational function the clutch provides and preventing the button from being used again 

The space movement of the console printer is triggered two independent ways. One is triggered by a cam at the end of each character print operation  - this one works fine. The other is triggered by an operational clutch fired by either the solenoid or the front panel pushbutton. This is the one that didn't work. 

The torque bar that lets the carrier be pulled forward one space is common to both methods. The rod coming from the print cycle mechanism will pull on the torque bar, with the length of the rod adjusted to make sure it activates the space when pulled but allows the carrier to stay locked on a column when it shouldn't be moving. 

Another mechanism has multiple parts that rotate and then convert that into a downward pull on a small hook which pulls on the torque bar but slips off before its pull motion is complete. Slipping off is essential so that it doesn't hold the torque bar too long and allow the carrier to move more than one column to the right. On the other hand, the hook must engage with the torque bar and pull it far enough before the hook slips off, so that the torque bar is rotated enough to release the carrier reliably for its one space movement. 

Several adjustments interact to get that arm to move the proper amount and slip off when the operational clutch for spacing is tripped. The clutch takes a 180 degree spin, in doing so it pulls down on a spring loaded lever that is coupled to the other parts that ultimately move the hook up and down. The hook is spring loaded to rest over the torque bar but the spring is light so that the hook can slip off the torque bar when it turns enough to release the carrier. 

Lack of the ability for XIO to put in spaces will only impact me slightly with the diagnostics. The text of a message will be smooshed together without separation of words, but otherwise legible, because each letter printed will get its own space during the print cycle. Therefore this adjustment can be postponed until later, letting me proceed rapidly to the disk functionality diagnostic 309.