Errors reading paper tapes

[RSX11M+]

I remember the ASR33 as being unreliable reading paper tape, but why? ...A telex machine is the same and they work fine. Doesn't the ASR33 use pins to sense the holes in the tape?

I used an ASR-33 in my first year of High school and all of college. I never had an issue reading tapes that were undamaged, unless the machine was so contaminated with punch-outs that it bound up. However, almost all the tapes I fed were either made on that ASR-33 or another. Original DEC tapes were never in our hands, unless sitting in front of the system, and then tapes were fed there, and kept there.

Most of the time was not spent in the computer center, but off-site. [think of a room with rows of ASR-33's]

Perhaps reading mass-produced tapes was always a problem for them, or ones like those you're finding would have been.

It doesn't seem so odd or mysterious when I think about it that way.

My ASR-33's reader is constructed like all the ones I recall, with a "Sprocket Wheel" to drive the tape. The pins on the wheel poke through the indexing holes and drive the tape precisely along. The read mechanism is synchronized to the wheel, but obviously such a design will have difficulty reading a tape with that much hole spacing variation. Elongating the data holes slightly toward the "expected" location should work fine, as long as the variations aren't so bad so often that the running average of about 3/4 inch climbs off the sprocket.

 

[tradde]

I used an ASR-33 in my first year of High school and all of college. I never had an issue reading tapes that were undamaged, unless the machine was so contaminated with punch-outs that it bound up. However, almost all the tapes I fed were either made on that ASR-33 or another. Original DEC tapes were never in our hands, unless sitting in front of the system, and then tapes were fed there, and kept there.

Most of the time was not spent in the computer center, but off-site. [think of a room with rows of ASR-33's]

Perhaps reading mass-produced tapes was always a problem for them, or ones like those you're finding would have been.

It doesn't seem so odd or mysterious when I think about it that way.

My ASR-33's reader is constructed like all the ones I recall, with a "Sprocket Wheel" to drive the tape. The pins on the wheel poke through the indexing holes and drive the tape precisely along. The read mechanism is synchronized to the wheel, but obviously such a design will have difficulty reading a tape with that much hole spacing variation. Elongating the data holes slightly toward the "expected" location should work fine, as long as the variations aren't so bad so often that the running average of about 3/4 inch climbs off the sprocket.

I read many a paper tape back in the day. Both those produced from DEC via DECUS and 3rd party. Some were
quite large. I do not remember ever having a problem reading any tapes on any ASR we had access to.

 

[woodchips]

Yes, the punching error is rather pronounced. But the tape is fan fold, we only ever used reels for machine tools, perhaps this is why. It seems obvious that the fold in the tape has caught causing the misplacement, but then again you would assume the sprocket to have more than one hole engaged? The other possible difference is that optical reader and punches punch the sprocket holes before the tape goes under the data hole punches, simply to make sure some holes are there. A mechanical punch like the ASR33 punches all holes, data and sprocket, together simply because that was the way they were designed.

Has anyone got one of those paper tape repair blocks? Small steel block with a grid of data holes and a small punch. You had these self adhesive tabs that you stuck on the tape to repair it, and then punched the old or corrected data hole pattern into the tape. Even so I don't remember them having the facility to correct the sprocket hole position, the tabs had them already punched. Not seen one for decades, can't be that hard to make.