SW for drawing logic diagrams

Yes. Horrible machine. Later we got Decwriters and then Datapoint CRT terminals. All kilobucks, which would buy a small new car in those days.

Yes indeed.

But the ASR33's "press hard and wait 100ms for the thump" as the character appears is /so/ evocative of a time, place and age.

The Decwriter's screech is just that, and no more.

I was getting errors on my ASR33 paper tape reader, so I shot a sptitz of SprayKleen contact cleaner into it. The polycarb tape guide, in about 1 second, crazed and flew out in pieces.

From what I've been told, one of the big issues with the KSR33/ASR33 teletypes is that they had originally been designed for a modest (intermittent) service duty cycle. They really weren't built to stand up to full-time use, such as they got in our college's user computing center. The college had one good tech-student (a guy named Ray) working hard to keep the fleet of a dozen or so in service, but it was a losing battle... they were just wearing out.

One ASR33 in particular had a glitch in its tape-reader system. Occasionally the tape reader would kick into "read tape" mode for no good reason, and try to read a few characters even though there was no tape in the reader, and then stop when the "no tape" switch actually closed properly. Since there was no tape to block any of the hole-sense pins, it would always read RUBOUT characters... which the operating system in question used as a "delete character" code.

A friend of mine had read in a long tape - a thousand or so lines of code for his Star Trek simulation game. He was in the middle of a complicated editing session, and had just typed in a command to delete two or three lines from the middle of one section of code. He typed something like

DE 1435.001-1435.004

and the ASR33 kicked into READ mode at just the wrong moment and rubbed out a few characters of his command. His "type and hit return" finger-sequence ran to completion before his reflexes kicked in, and the computer actually saw

DE 1435.001-14304

I heard him say "Oh, shit"... he hit the BREAK key, and the computer responded

Command interrupted. 1653 lines deleted.

There was a loud "DAMNIT!" and a ferocious BANG as his fist came down on the metal plate on the right side of the ASR33 case. The plastic body immediately cracked. He stomped out in high dudgeon, having lost at least an hour's work. (The college hadn't assigned students enough disk space to let him save his work incrementally, alas.)

I think they retired that particular ASR33 as non-fixable not long thereafter.

(I swear, if I think back, I can still smell the characteristic odor of ASR33 paper tape chad. I've had enough of it in my clothes and hair through the years...)

I beg to differ. For a time in college, I rebuilt, repaired, and refurbished various teletype machines. I liked the Model 33 ASR because I could easily obtain parts and documentation. Keeping them running was mostly adjustments, regular lubrication, and keeping the moving parts free of dirt. Still, there were those who failed to appreciate the technology:

AP, UPI, most news outlets, Western Union TWX, and the weather services would disagree. They ran their machines 24x7 and replaced them when something wore out. The company I worked for would rebuild these worn out machines, and put them back in service. They may not have been designed to run forever, but they were designed to be repairable and maintainable, which might lead to running forever if they were properly maintained. However, you might be correct about later electronic models, where the electronics was would fail quite often and was expensive to replace. That coincided with the introduction of more plastic parts, which were also failure prone.

Incidentally, if one followed the service instructions in the manuals, a typical Model 33 ASR/KRS had about 400-500 places that needed to be lubricated.

The problem with "tech-student" based repair is that the student only lasts 4 years. If the skool was smart enough to have him train his replacement, such a system might work. If not, maintenance of the machines will be spotty at best.

In college, I spent one summer working for the skool calibration lab doing "catch up". The backlog of unrepaired equipment was huge and filled to storage rooms. My instructions was to fix what I could and don't spend any money on parts or manuals. I did quite well cannibalizing parts out of other pieces of test equipment and begging for manuals from the major vendors. The lab manager was smart enough to realize that I needed to train someone to replace me as I would shortly be graduated. However, the only students available were my age, which wouldn't work because we would graduate at the same time. I'm told the student repair system fell apart a few years later.

It should have deleted only one character, not three. Something else is wrong with the machine.

Yep. DEL, rubout, or delete) is ASCII 127 or seven 1's. The teletypes of the 1960's would end lines with CR, LF, and DEL (carriage return, line feed, delete) to add a delay and fix a CR timing problem. The Model 33 ASR/KSR would work correctly without the extra DEL at the end of a line at 60 wpm (words per minute) but screw up at 100 wpm. Sometimes, I would see several DEL characters at the end of every line because of extra drag from congealed oil on the carriage would extend the CR delay.

Anyway, with a program that long, he should have been punching a new tape or card deck, and trying to punch it directly into the computer. At 10 bytes/inch for paper tape, 1653 lines = 1653 inches = 138ft Yeah, that's a long program.

Interactive programming was quite risky in the time share and teletype era. My usual routine was load the old tape, edit on the console or on the teletype machine, punch new tape, and then run the program. A bit tedious and wasteful of paper tape, but less risky.

Gluing the plastic was futile because of all the oil. Glue wouldn't hold and if it did, the solvents in the oil would soften the glue.

I became rather proficient at gluing paper tape segments together to produce long programs.

How Model 33 ASR teletypes are retired:

What you smelled was the oiled paper tape. I don't recall what type of oil was used but I suspect it was the same was what was used to lubricate the paper tape reader (10 wt light machine oil).

Oh, I'd forgotten that, especially with the 5cps teletype class machines. I was taught to use cr,lf,cr, to make sure the carriage really had returned.

Well, there are other ways. You could tape the ends of the paper together forming a loop. That way any wires that need to run the full length of the page, would at most need to only run half way around the loop. Also, if you run out of space, you could half twist one edge tape the edges, and form a Mobius Strip: That provides twice the paper and retains the benefits of a shorter maximum line length between points.

If that's true, then they have no need to balkanize a schematic into small pieces. Instead the schematic can be saved as one big drawing, and viewed in small pieces on the screen. I also do it this way but prefer JPG schematics that seem easier to edit and annotate.

I'm really a throwback to the stone age of design (and programming). I still print or plot the schematic, scribble all over it with a red felt tip pen, and clean up the mess when I'm done. When the old methods works well enough for me, I don't need anything new and improved. The only problem with my method is that I can't seem to avoid burning the print with my soldering iron. Perhaps when I can buy a cheap LED computah projector, that has the resolution needed to display an enlarged section of a schematic without smearing, I might change my ways and go fully paperless.

I believe that very phrase is a quote of the dinosaurs.

Rick C.

That would also work, except that most of the news service machines had an auto-LF modification kit installed. With auto-LF, two CR's will generate two LF's, or double spacing. One only needed to send a CR at the end of each line. Sending one CR and no LF was important because they were paying the telegraph TWX companies by the character An extra character or two at the end of each line was expensive. Most of the other machines did not have the auto-LF kit, so an extra CR would have worked.

The timing problem was most apparent in machines that had been converted from 60 wpm to 100 wpm by replacing motors and timing gears. Machines that were supplied from the factory for 100 wpm had an extra strong return spring on the carriage. That worked well when properly lubricated, not so well when the lube turned to tar, and really awful when bone dry. Without oil, the carriage would literally fly at high speed CR, slam into a rubber stop, and sometimes shake the machine enough to interfere with the operators typing. When the rubber stop finally wore out from the pounding, the carriage would make a loud bang when it hit the stop. If left to pound in this condition, the carriage would eventually strip the threads in the stop mount. Fortunately, replacement was easy. My guess(tm) is about 1 in 20 machines were like that.

And makes it impossible to read but it's a good hallucination.

CAD systems are paper based. There is no 'Z' size paper.

We're forced to use schematic symbols that look like pin diagrams of all flatpack (i.e. other than BGAs) devices. 144pin QFPs take a lot of space, so don't fit on small pages. Schematic pages pretty much have to be D-size, so they're a little large to spread out around our cubes (also our lab). Shrinking to smaller paper makes them hard to read so, while I do it, it's just for quick reference (and markup, as you note). I'll still have the schematic open on my computer.

====snip====

Sorry to burst your (thought) bubble but that last statement is false. Topologically, all you've done is doubled the effective length of the paper loop's continuous surface, meaning there's no magical halving of the average connection point distances between randomly selected points within the whole schematic diagram.

Unless the point of the exercise was merely to 'save paper', you're no better off than when you had created a simple paper loop with an unused back side. Being a loop, Mobius or otherwise, you'd be forced to scroll your way through the schematic, admittedly in whichever direction offers the shortest path to the next region of interest on the diagram.

In this case, you might as well keep it stored in a suitable container file and use whatever editing software is appropriate to the task and scroll around your arbitrarily sized diagram on a workstation display.

There's no need to limit yourself to choosing which of two edge pairs are to be joined to create a loop (normal or Mobius) when the editing software can let you work with a rectangular page and allow you to roll over opposite edges of the page.

Whilst the printable version will need the use of "other sheet" style links for the edge to edge transitions, the editing software can, if preferred, automatically let such links display as uninterrupted circuit traces or lines crossing each edge transition as you scroll through the diagram on your workstation display.

The college could have bought ASR35 machines,designed for heavier use.

mentions them under "related machines". I knew about them in the late 1960's. but only by repute.

Everything I did in 3 colleges was on punched cards or magnetic tape on a GE-415. The only paper tape was on the Slo Syn CNC machine controllers, the ham radio station, and the music player for the clock tower carillon. In all cases, the tape punch and reader were separate units, not attached to a teletype console.

The Model 33 ASR weighed 75 lbs (34 kg) with the stand. The Model 33 KSR (no paper tape punch or reader), weighed 65 lbs (29kg) with the stand:

There was a schleppable version of the Model 33 that allegedly fit in a small carrying case: I've never seen one.

Including the desk, the Model 35 weighed about 100 lbs (45 kg): Notice the difference in size. I don't believe that there was a portable version.