Collecting data on the failure to autoload tapes or dump into the vacuum columns

WATCHING AN AUTOLOAD ATTEMPT WITH ACRYLIC COVER

This was quite interesting to watch. I attempted this about five times, all unsuccessful. The first was the most successful try.

The tape did indeed thread itself around the perimeter and out to the take-up reel hub but it stopped threading too early. It should have fed more tape and wound it a few times around the hub before switching on vacuum and attempting to dump into the columns.

The remaining attempts never got that far. Once the supply reel refused to turn at all. The other times it fed in part way then gave up and rewound onto the supply reel a few seconds.

WATCHING AN ATTEMPT TO DUMP A MANUALLY THREADED TAPE

I began with the tape manually threaded through the machine and around the take-up reel, pushing load with my acrylic cover held in place. In fact, the tape did dump down and form the two loops midway into their vacuum columns, but the machine then recognized a load check and dropped vacuum. I need to see what other failures can lead to the load check symptom, as my problem may be elsewhere.

IMPLICATIONS OF WHAT I WATCHED

First, I was concerned about the one case where the supply reel didn't move at all. It has worked reliably every other time but it might hint at some unresolved problem.

The time it threaded successfully we either ran out of time or didn't set sufficient time to wind the tape around the hub a few times. I had to investigate this.

Using my scope I watched the test point that shows me timer intervals. The 5.5s timer was measured at 5.0s, a bit short but somehow this can't be the whole story. Perhaps the turning speed of the reels is too low, or some key signal is not being processed. For example, when the tape begins to thread into the path, it has only 3.5 seconds on a timer.

During that time, the BOT sensor that looks for the bright start of tape reflector should go dark as the tape passes that point. This resets the timer to 5.5s which ought to mean that we have at least that amount plus whatever time was used to darken the BOT photocell.

The problem is that I don't really know what is normal. Is the reel turning too slowly? Is the time interval a bit too short and causing the problem? Is there another defect on the control board or with the capstan that I haven't detected yet?