Drilling down into failure of drive A 'dump' of tape into the vacuum columns

LOGIC ANALYZER SET UP CHANGED SLIGHTLY

Since the visual evidence showed that the failure is occuring in the upper vacuum chamber, fed by the supply reel, I can remove the signal leads from the lower chamber and instead use those leads to monitor the pressure/vacuum differential switch signals that trigger changes in the loading state machine.

I believe that the switch recording vacuum in the chambers will activate (go low) at the start of the dump sequence. This is where the supply reel will move clockwise to allow the tape across the mouth of the upper vacuum chamber to be sucked downward.

The loop of tape in the chamber should pass across four photocells near the top of the chamber, the reel should stop at that point and the tape loop should NOT pass across the other four photocells at the bottom of the column.

RESULT OF ATTEMPT TO LOAD MANUALLY THREADED TAPE

I was not happy with the reliability of the data I was collecting. Depending on where I push on the acrylic cover, I get different failure results. In one case the tape edge folded over instead of sliding down the column in a loop. I think the plate flexes enough that if I push within a column it narrows below the width of tape.

The logic analyzer did record signals but I never saw the vacuum signal go low, in spite of the fact that something triggered the capture. Without seeing the signal go down, I can't trust what I am seeing. Either there is some change I need to make to the logic analyzer software in the Analog Discovery or I have to move over to my full size dedicated analyzer.