Teletype ASR 33

[billdeg]

I knocked over my working teletype ASR 33. One of those things-go-into-slow-motion moments...NnnnooooooooOOOO! Craaaash!!

I has just finally got the machine to fully produce a carriage return cleanly the day before too it was fully functional with no electrical problems. I was even able to punch code dumps from memory, and I was just about to save my first program.

OK

After locating all of the pieces, I carefully re-installed as much I could. The whole thing came apart, little pieces everywhere. The typewriter became detached from the keyboard. Pretty bad.

I almost got it working, but there is one thing that I cannot seem to fix.

The problem is that the print head is not moving horizontally along the line, it just says in place and types each character on top of itself.

I do know that the teletype is sending data correctly from the keyboard to the computer through the serial cable, and the computer is receiving the commands. Output from the computer to the teletype is received and the print head itself is printing the correct characters. The problem is that the print head is not being moved to the right/horizontally. I can manually move the print head while in a operation (I can send a punch command to the printout paper for example) and if I time it just right I can space out the printed characters manually so I can see what has been sent from the computer.

Can anyone help identify the problem?

I have taken pictures, but because there are so many cams and sprockets I am not sure what to take a picture of.
http://vintagecomputer.net/browse_thread.cfm?id=279

I have the documentation, and I will continue to work to solve, I am pretty pleased that I was able to unbend the cams and such, and re-connect the keyboard to the typewriter part. There is that little sideways H-shaped connector piece that makes the connection between the two major sections. I also learned that the keys are loosely installed inside of the keyboard so you have to be very careful when you take the keyboard cover off.

I would be willing to travel to someone with experience who repairs these (w/i 250 miles of Wilmington, Delaware), we can talk offline about service fees/trades. I have a lot of spare teletype and other parts. Worst case I guess I will offer buy another stock ASR 33 if anyone has one and this one can't be fixed.

I am going to post this request to classic cmp too.

Bill Degnan

 

[pontus]

I can only sympathise, I do hope you get it pieced together again. They are pretty sturdy so one can hope that it is just a matter of getting the right bits in the right places.

I think there are scanned drawings on bitsavers.

 

[nige the hippy]

well... guess what I picked up yesterday!
A few issues, the carriage wasn't returning, that was down to the spacing ratchet (i.e. the pulley assembly that drives the carriage belt) being stiff with old grease, an unresponsive keyboard (down to the keypress sense bar pivots being a bit stiff (grease-swollen nylon... a bit of a problem, can of squirty degreaser & some patience I think) and in the same area as Bill's problem.. no spacing with the space-bar, so I've been paying a bit of attention to that area.

Firstly on Bill's, the carriage return latch is holding both the spacing ratchet pawls off the ratchet (33-1, centre), which is probably why the carriage isn't advancing (hopefully the ratchet isn't stripped too, it looks a bit silvery) this latch is tripped by code sense lever under number "3" on the left hand function lever casting, and "afai-can-tell" held tripped by the function pawl in the back of slot "B" there also seems to be a separate latch pivoted around the base of the spacing ratchet which is tripped by a lever on the pivot of the carriage return spring wheel, when a pin on the carriage presses it when the carriage gets home. I suppose either of those latyches could be jammed on, or it could be that the pin on the carriage (or it's target latch) is bent so it's never resetting.

Good luck!!!!!

 

[billdeg]

Thanks for the replies.

I was able to make progress by comparing with photos from the web suggested to me from a fellow computer club member in MARCH. If you get a teletype, make sure you not an obsessive compulsive or you'll be in front of the thing for days ...

I am not sure if this helped fix the problem but it turns out that I was missing the piece that catches the carriage when it returns to the left position after a return carriage. This piece may or may not also help with the catch arm for the horizontal movement. If you have a teletype, there is a little clamp that goes on the belt that has a little metal stopper. When the carriage gets all of the way to the right, the belt comes up against the stopper and rings the bell.

Anyway located behind this catch arm I stuck my finger on the sprocket in an effort to put pressure on the cog that moves the carriage horizontally as the typewriter prints. I am not sure if that makes sense, but kind of flicking it clockwise at just the right time (against the direction of the belt) I was able to create pressure and cause the latch to catch into the horizontal sprocket and cause the typewriter to print the line correctly. For a while I did this manually, and eventually the sprocket started catching on it's own.

So now I need to fix all of the keys, they're not all in the correct alignment. Most important to the SWTPc 6800 (that's running the teletype) is the "M" key as in M 0000 (show me whats in memory location 0000). I have been using the P command to dump the contents of the monitor to the printer so that I can keep the system printing while I test.

I estimate another 5 hours of tinkering to finish the job. I really should, now that this is fresh in my mind, disassemble the whole thing again and re-construct. It needs cleaning. But that's my compusive nature calling. These are mechanical beasts, nothing like computer repairs, more like fixing a typewriter. A few years ago I was able to fix an IBM Selectric, kind of similar.

Bill

 

[nige the hippy]

does sound a bit like there was maybe a bit of poop jamming the carriage return latch on.
I'm fixed too! a bit of squity alcohol & some silicone grease on the left "T" lever of the keyboard actuator codebar & keyboard is responding fine. I remember blanching the last time I was faced with a teletype with no top on the keyboard, I've had this one on & off about 5 times so far! The spacing problem has just gone away too, I don't know why. The carriage advance pawl wasn't quite going to the right place, I was going to adjust the roller that drives it, but maybe fiddling has pushed it a bit. I suspect that one's going to come back.

This unit has (now) only 311 hours on the clock! but before yesterday it hadn't run in 20 odd years. No exploding caps yet.

I'll take a photo, it's in a funny box, I was considering trying to get a teletype top case for it, but the odd enclosure is growing on me.