Saturday, September 8, 2018

Teletype and Sherman Tank progress


Ken and I completed the wiring of all AC and DC power on the table. During that process, we checked all the lines for correct connections and absence of short circuits. We did discover two shorts. One was caused by frayed wiring connected to a receptacle, and the other came from wire whiskers  bridging between adjacent terminal on the Transmitter/Distributor connector block. 

The desk has two power switches on the front. One controls the motor on the Transmitter/Distributor and the other controls the REC-30 Power Supply. I checked their operation and found a fault in the Power Supply switching. We discovered that the switch itself was stuck open. It was a double pole, single throw 20A switch which had been wired in parallel to support more than 20A load. 

We picked up a suitable DPST 20A switch from a local hardware store and installed it, restoring the ability to switch the main power supply on and off. 

I began to wire the signal lines, supporting twin lines, a mix of Reperforator, Transmitter/Distributor and Printer/Keyboard plus test plugs. The last set of connections to make come from the complex line switch that supports connecting the reperforator to either of two lines or leave it offline. There are also connections from a Tape Out button that provides idle characters as filler to provide some leader or trailer on a tape being punched. 

We all worked to install the base and connector block into which the model 14 Transmitter/Distributor will slide. This was finished and all the wiring completed, thus we can use the TD as soon as the signal wiring of the desk is complete. 

Marc spent some time putting together the cover for the model 15 printer that will sit atop the desk. There were several doors and flaps that were twisted and fitted badly. Marc spent the time bending these until the closed and opened properly.


Mike did a teardown of the selector mechanism in the reperforator, both to improve its operation and to support some video demonstration of the way that teletype selectors work. 

Mike and Marc designed and installed a modification providing a terminal strip for connections to the reperforator, which provides a neater and more reliable alternative to the directly soldered wiring of the original mechanism. 

Mike did quite a bit of oiling and exercising of all the moving parts. It is largely done now, with most levers or other parts moving easily and promptly. 


Marc's Transmitter/Distributor was assembled and all wiring completed. He did a sequence of adjustments until it performed perfectly. He demonstrated this with a tape he had produced on his keyboard perforator, transmitted flawlessly to his model 15 printers. 

I picked up new brushes to install on my Transmitter Distributor, but for the time being I am waiting until we can manufacture or find a motor pinion supporting the standard 60 wpm transmission speed. 


Nancy selected the tank body color and did a test painting. We are ready to prime and paint all the panels of the tank now. We are still struggling to find right material for tank treads and wheels. 

I spent Saturday building out the front half of the upper body and doing some finishing of the center 'bar' section. We have a few more plywood panels to install but the majority of the front half of the tank is done. I expect to wrap this up on Sunday and to begin building the rear half of the upper body and the rest of the bottom panels. 

Most of front upper body is done, but some panels left to do

Bartenders side view of the front of the tank (sans Turrent on top)

Tuesday, September 4, 2018

Starting on Sherman Tank bar construction


I began construction of the latest bar structure we are building for the Villa Siena fundraising dinner. The theme of this dinner is WWII/1940s and the design we chose was a Sherman Tank. We have to accommodate bartenders inside which requires this to be big enough to allow for a ten foot wide window across the bar where drinks are served.

The structure is a side of a tank (actually half a tank as it is cut along the front-back centerline), with the main gun barrel facing left. The structure is 21 feet long and five feet deep. The top of the treads are 4 foot off the ground and the bottom of the gun turret sits about 7 foot off the ground. This is slightly larger than life size scale, where a real Sherman tank is only 19.5 foot long.

Structure - picture distorted due to need to use Panorama mode to capture image
We built the frame for the bottom of the tank (up to the top of the treads) with the higher window opening for the bartenders taking 10' of the length and nearly centered front to back. It consists of a front, a back and the center bartender section, allowing us to move the parts; these but side to side to form the 21' length. The center section can be separated to fit past gates and openings around my home.

The body of the tank consists of a front and back half that will sit atop the structure you see here - these rise to about 7' above ground over the center section and form the outline of the tank, minus the turret. We have to build these front and back body pieces next and sit them over the frame you see.

The turret itself will be formed from paper mache, using chicken wire as a form to apply the paper. That will attach to the top of the body sections we will build next. 

Saturday, August 25, 2018

Work on model 14, 15 and 19 teletype parts


Marc is in contact with a fellow YouTuber who does CNC work on gears to see if he can make a replacement for the motor pinion gear I would need to hit the standard 60 wpm transmission rate (about 6 1/8 rotation per second). This is achieved by taking the 1800 rpm synchronous motor, putting on a 9 tooth pinion gear and coupling that to a 44 tooth gear on the main shaft. 

I am also pursuing a possible source of another 14 TD which might have the right gears in place, but it will be a week or so before I know if this will pan out. 

We worked to get the wiring of Marc's TD correctly installed. Once that was completed and verified, he continued to install the labels, covers and other parts to finish this up. Next week he will run a test to transmit the contents of some test tapes to one of the model 15 printer units.


My model 15 teletype has a bent typebar for the letter Z which results in the letter printing faintly in the superscript area above the line of the other typed characters. This is due to a deformation of the shape of that typebar, which sits on the outside edge of all the typebars on the carriage. 

Z typebar prints too high compared to other letters
I can see from the rest position of the typebar that it is bent out of position. The typebar shape is complex, with several bends the ensure the typeface strikes right in the middle of the ribbon opening, flat and at the proper height. To fix the misalignment, I need to adjust several of the bends. I am studying and making a detailed plan for the bending necessary.

Leftmost (Z) typebar out of position

Ken and I began to install all the wiring, receptacles and switches into the desk today. Fortunately, the Teletype company drew up a wiring diagram, which is distinct from the more usual schematic. The wiring diagram shows each part in place with the actual wiring that is connected. This includes the jumpers that connect different terminals on the terminal blocks.

It goes so far as to identify the wiring bundles that are laced together with string - in one long group of wires there are several bundles. Each bundle runs to one or two receptacles and I can distinguish them by the number of wires hooked together. A circuit continuity tester gave me resolution to the individual wire in each bundle.

By the end of the day, I had two fuses and five receptacles fully wired, additionally I had four phone jacks wired but not fully verified. Ken had three switches on the front of the desk wired and the power lines installed through the flexible armored cable and

Finished wiring receptacles and fuses while the signal jacks at right are nearing completion
Power switches and one armored conduit installed, more to do on right
The wires from all these receptacles, fuses and switches run to five terminal blocks that connect together the 110VAC, 120VDC, send, receive and test lines. There are quite a few jumpers that run from one part of the terminal blocks to another part. Many of these are loose and have to be replaced as part of the wiring. I still have to install the metal stands that the five terminal blocks attach to, then complete the wiring.

Terminal blocks being wired and tested, but not yet mounted in place

Mike Albaugh brought over his typing reperforator. This is a unit that will take the incoming characters from the signal lines and punch them on 11/16" paper tape, using a chadless method that leaves the hole with a hanging chad.

In today's terms, because of elections, we think of chads as things that hang attached to the main paper, but the original terminology calls the completely removed circle of paper a chad and that chad falls into a waste chute. If the hole remains partially attached, it is called chadless by Teletype.

The reason that the hole is only perforated partially is to leave the paper in place since characters will be typed on the tape. If there were holes, the characters would be obscured by the holes. This way, you can read the typing on the paper tape but the pins in the Transmitter/Distributor will push the flap away and accurately detect where a partial hole was punched.

This unit has a selector unit and typebars, much like the model 15 printers we restored, but it is quite a bit less complex in many ways. No function box since actions like tab, carrier return or line feed don't make any sense when performed on paper tape. Instead a special character is typed that represents each of those functions. Thus, this machine only needs type bars to print all the letters, figures and control function characters.

When Mike got it wired up, he found that the selector mechanism was too gunked up to perform properly when we tested it. The motor and solenoids were moved and it was dunked in Simple Green to remove old lube. At the end of the day he began to remove, reassemble and lubricate parts of the typing and punching mechanism. It will take at least another session to get this working properly. 

Tuesday, August 14, 2018

Successful trip to RTTY Electronics for teletype parts


On Monday five of us journeyed to visit Paul Cemburas, Mr. RTTY, of RTTY Electronics, who maintains an enormous stock of teletype parts, machines and related goods. We had previously sent him a list of parts that Marc wanted, a list that Bob wanted and a list that I wanted.

My parts included missing items from my model 15, a spare part I wanted for my model ASR 33, and new gears for my model 14 TD to convert it to 60 wpm operation. Marc had a similar list including thumbscrews, the glass panel for the cover and the hand crank to advance the paper manually on the model 15. Bob Rosenbloom has a longer list because of the large number of machines he has to restore.

In spite of an enormous collection of parts, each of us had requests which could not be fulfilled. For example, both Marc and I were interested in buying the crank that is used to manually space paper up out of the machine, but they are very rare. We saw one in person and admired it, but none was for sale.

Converting my model 14 TD requires a matched pair of gears, one on the main shaft and a smaller pinion gear on the motor shaft. Paul had a partially machined gear for the main shaft but no pinion gear. Once I drill mounting holes in the gear I could install it, but not until I find a pinion to match.

Marc did have a pleasant surprise, finding that he could add the motor stop optional feature to his model 19 system. The model 15 he owns has this feature, allowing a user to start up the motors of the teletype, send a message and then power down the motor by sending the Figures-H character.

It consists of many dozen brackets, levers, screws, spring and other parts, installed on both the baseplate and the printer modules. Marc decided to check availability of the parts, using the parts catalog to generate a long list of part numbers. Amazingly, Paul had every single one of the parts in stock.

I was unable to pick up the stock line feed upstop for my ASR 33, nor the model 15 parts I was seeking. None of them were critical - two rubber guides that position the cover over the baseplate, a new drawstrap for carrier return, and the unobtainium hand crank.

Bob did pick up quite a few parts that he requested, although some parts such as the cover plates for the front of the model 33 teletypes were unavailable. Overall, we were all satisfied with our trip. Plus we saw many rare and unusual teletype machines.

Saturday, August 11, 2018

Progress on model 14 Transmitter Distributor restoration and a motor investigation


I disassembled my model 14 and oiled everything on the main shaft in preparation for trying out a potential new gear set. The gear I received from RTTY Electronics needed some holes drilled but was otherwise cut with the necessary number of teeth to gear the synchronous motor down to the 60 wpm rate we wanted.

Marc had some gear sets he received with his teletype, but none of the motor pinions fit my gear properly. It meshes perfectly with the 80166 gear on his TD and that is the part I still need to make this unit work at the intended rate, rather than the faster 75 wpm rate it was geared to produce. 

The clutch on my TD is a later type, a drum clutch, unlike the friction clutches on most model 14 TDs including Marc's unit. This has shoes that expand under spring pressure to rub against the inside of the drum when the clutch is engaged, then they retract when the clutch is disengaged after one rotation of the shaft. 

After lubricating all the parts I tried to reassemble it. There is some trick I have to learn to compress the shoes in order to fit them up inside the drum; I wasn't successful on Friday in figuring out the needed technique. 

I partially reassembled my TD and set it aside for when I have a new pinion gear, at which time I can also complete reassembly of the drum clutch. If I don't find or make a suitable pinion gear for 60 wpm, then I will need to reassemble the old 75 wpm gear set and make use of an alternate method to slow down the TD. 

I have a number of methods that could be used to make my model 14 TD produce teletype serial streams at the 60 wpm rate:

  • buy or make the pinion to mate with my new main shaft gear to operation at 60 wpm
  • use a variable frequency drive to slow the frequency of the mains down and slow the motor
  • build a box that will accept and buffer data at 75 wpm and drive a 60 ma current loop at 60 wpm

Marc worked on his model 14 TD. It had been disassembled to send the base and covers out to be powder coated. With the coated parts on hand, he began assembly of the unit. Most parts went together easily and the wiring was obvious. The wires to the main contact plate, however, don't match the schematics or other TD units, which was where he stopped at the end of the day. 

Ed had bought a synchronous teletype motor to disassemble, as he was curious to see its construction including the motor start winding and its centrifugal switch. He pulled it apart although it was not obvious that the bearing on one end would pull the centrifugal switch mounting bracket off with it. This stripped out the two small screws that hold the switch to the end plate.

Ed picked up a replacement plate and screws from RTTY Electronics. While there, he also picked up a new set of brushes for my TD. The brushes slide on the brass rings on a disc, making contact to route the various pinhole microswitch contacts from the paper tape reader to the serial output line. 

The brush that rides on the segmented ring, the one that breaks a rotation into a start bit, five data bits, and 1.42 stop bits, was worn down quite a bit by the action of the slots between segments. The other ring is continuous and its brush was much less worn. 

My Model 14 paper tape reader is the wrong speed, but we make continuing restoration process on the Teletypes


I was given a transmitter distributor, which is a paper tape reader for the 11/16" 5 bit baudot tape used with older teletypes. At our work session with teletypes we worked on two of these units, one that came with Marc's model 19 system and one that I was given. As well, Marc made some adjustments to his model 15 teletype to correct two flaws we had discovered.

The model 15 has a feature that will stop the motor based on a character sent to it (motor stop is the H key in Figures mode), then restart the motor if new data begins arriving. One function of this feature is to flip the switch from SEND mode to RECEIVE ONLY mode during a stop. 

We had found that it was bouncing the switch nearly out of SEND mode on every typed character, and from time to time it would move it all the way to RECEIVE. This was frustrating to users trying to type messages on the keyboard as it would suddenly stop sending their keystrokes. 

Marc did some adjusting and it now works perfectly. The lever doesn't bounce at all except when seeing an H character (H key in Letters mode), where it moves just a bit but never forces the lever to RECEIVE ONLY. When a stop is sent (H key in Figures mode) it will flip the lever to RECEIVE and stop the teletype motor. Worked correctly every time. 

The other flaw we had discovered was with the autorepeat feature for the spacebar on his keyboard. This is designed so that a normal tap on the space bar produces exactly one space character, but if you press down hard on the bar and hold it, a string of spaces are emitted until you release the bar.

On this keyboard, it would autorepeat on any tap, so that single spaces were usually turned into 2 or 3 in spite of how briefly the typist hit the bar. Marc adjusted the mechanism until it was performing perfectly, providing single spaces unless you intentionally pushed down the bar and held it. 

Marc's TD (Transmitter Distributor) is disassembled, since he had the cover and baseplate powdercoated along with the rest of the model 19 external metal surfaces. He spent the time cleaning up dirt and corrosion from his parts, adjusting it properly and cleaning all the contacts to remove old oxidation. Someday soon he will begin reassembly of the TD. 

My TD needed cleaning and relubrication before I could test it. I spent time freeing up mechanisms, scrubbing off dirt and cleaning most of the corrosion on metal surfaces. I then cleaned the contacts and inspected the unit carefully. It appeared ready for a test, but we had to provide connectivity first.

The model 14 TD has a set of metal contact fingers on the back which are intended to slide into a baseplate such as the desk from Marc's model 19 system. We worked out the required wiring to provide 110V AC to the TD and hooked up the current loop for the output signal. 

I crimped ring terminals on some wires including a phone jack cable for the data output and a household plug cable for delivering power. These were hooked to the appropriate fingers of the contact mechanism. 110V is provided to two fingers to power the AC motor and to two other fingers to power solenoids that control function. The phone jack hooks to two fingers for the line common and MARK output side.

The TD is designed for both the normal NEUTRAL signaling method and POLAR signaling. NEUTRAL signaling delivers a 60ma 120V current for MARK bit values and no current to indicate SPACE. POLAR signaling delivers current in two different directions, one for MARK and the other for NEUTRAL. We wire our TDs for the NEUTRAL method we are using, but could use them to drive a POLAR line with a bit of rewiring. 

I fired up the TD and verified that the motor spins properly, a tape advances through the reader properly until it either runs out (sensed by one microswitch) or the tape becomes too taut and pulls up a safety switch bar. The result on the signal output line seemed correct as I pushed or released each of the five pins that sense/read the paper tape holes.

It was time to hook this in a current loop and see if the tape we read will be properly typed on one of the model 15 printers. Marc had produced a few test tapes with his model 19 keyboard, which has a paper tape punch called a perforator that transfers keystrokes into tape characters. I put in the first tape, holding a one line message, and transmitted it.

The results on the printer were gibberish. Having a suspicion that this might be a speed mismatch, we hooked up an oscilloscope to the line and observed the duration of the bits being produced. Our normal 60 word per minute units have a bit cell time of 22 ms and the stop bit, being 1.5 bits long, is 33ms. The scope showed a stop bit that was only 26 ms long.

We produced another tape, this one with a string of R characters, which would allow us to easily see and measure data bits. That confirmed that the bit cell was a bit more than 17ms, reflecting a transmission rate of 75 words per minute. The steady string of R characters produced gibberish on the printer, but a repeating pattern that further proved this was a speed mismatch problem.

I will need to replace the motor pinion and main shaft gears with a set designed for 60 wpm operation. We plan to visit RTTY Electronics to look around and buy spare parts on Monday, so that would be a good time to pick up the new gears I need. 

There is the complication that model 14 TDs had three different sets of gears for 60 wpm from a 60Hz AC synchronous motor. The motor pinion is always the same, but the main shift gear is one of three different part numbers. I am not sure which I should be buying, but hopefully I can spot the correct one when I look at them on Monday. 

We put the huge thyratron based model 30 power supply into service powering our teletype current loops as well as the perforator solenoids on the model 19 keyboard. Ken and Ed took lots of measurements of parts and watched the operation to understand this beast more thoroughly. 

Monday, August 6, 2018

VCF West exhibition this past weekend was a success


The exhibit at VCF West became one ASR 33 working and a broken one open on the table for inspection, two model 15 wired together to allow attendees to chat, and my model 15 printing the Reuters news feed. Near the end, we had a partially working model 28 join the other machines, as one of the team at our booth bought it from the show consignment room.

One of two model 15 teletypes linked together for chatting
My temporary fix for the line feed on the ASR 33 was erratic, but I had received a replacement bracket from a memory of the teletype oriented Greenkeys mailing list. I swapped that part into the machine, made a few adjustments and the line feed problem was fixed for the remainder of the show.

My print cylinder on the ASR 33 became more and more clogged with ink over the course of the show. I will need to remove it, soak it and get it cleaned up. This is the first of the after-show tasks on my list.

ASR 33 working with Altair 8800 clone
I noticed from reviewing the news stories on my model 15 that the letter Z was only partially printing and raised like a superscript above the print line. I looked closely and could see that the typebar for that letter was bent out of position a bit. Fixing this is the second after-show task on my list.

Model 15 printing Reuters news feed
My ASR 33 tends to print the first two columns crowded together, which I believe is due to a misadjustment for the carrier return mechanism. Adjusting this properly will be the third after-show task on the growing list.

I was lucky to have quite a few friends who worked the booth with me, engaging with show attendees and showing off the teletypes. In addition to the demonstrations I had planned, we added the game ZORK and had a few people trying out their BASIC skills on the Altair-duino and ASR 33.