Tuesday, October 31, 2023

Adjusted backspace function on 1053, built testbed to check out the printer under power


The way that backspace works on the Selectric is to implement a second rack just below the escapement rack - this one also with teeth but slanted in the other direction. A spring loaded pawl from the carrier will engage in the rack but just pops out of one spot and into the next as the carrier does its normal rightward spacing. When the rack itself is slid backwards, it grabs the pawl and pushes the carrier backwards. The escapement pawl will pop out of its rack and enter the previous column's position, completing the backspace operation. 

There are only two adjustments for the backspace mechanism, one of which sets up the proper play in the system while the second limits the maximum movement of the backspace rack. If the limit is too large, the carrier might hop more than one column back. If the play is too tight, wear can develop on the mechanism during normal forward movement of the carrier. I adjusted both of these. The main difficulty in making these adjustments is limited visibility, with the backspace pawl hidden below the escapement pawl, the tab pawl/latch and the tab gang clear bracket. 


So far my adjustments have been tested by manually cranking the main shaft of the typewriter. Some operations such as backspace don't work well with manual cranking; the need the extra momentum given by the rapid rotation of the shaft under motor power. Other functions appear to work properly with me pushing on a solenoid armature using a screwdriver. The most accurate test is to switch on the motor of the 1053 and to drive the functions using the solenoids and front panel pushbuttons. 

The solenoid is powered by 48V DC and one end is pulled to ground to cause the solenoid to trip. These activations should be relatively short, less than the time of one print cycle. Since the typewriter can operate at a maximum of 15.5 characters per second, this indicates around 60 milliseconds per cycle is consume. 

I decided to fire the solenoids for about half that, just to ensure that I don't request more than on space or character to print by holding the activation too long. To do this, I set up a testbed I can use to selectively fire solenoids during this phase of the testing. I will make use of a 48V power supply and a relay to switch the 48V feed to the typewriter on for only 30 milliseconds at a time. 

I set up a 555 timer with a button to produce the single 30 ms pulse, inverted it to match the particular relay board I have, and used that to control the duration of solenoid activation. This means that I need only connect a line to ground on the desired solenoid connection to the typewriter and push my button to request that function. 

I will begin with the operations that I feel are in the best shape - space, tab, index, backspace and carrier return. I will also test the upshift/downshift which spins the ball to the upper or lower case side, and test the color selection solenoids that would cause the red or black half of the ribbon to be struck by the typeball. 

I still don't have the ball rotation getting fully to the +5 and -5 positions, so I will not be powering any character typing until I think the issue is sorted out, just to be safe. 

Saturday, October 28, 2023

Oops on 1053 adjustment but fixed several others plus read another two boxes of 1620 cards for a different collector


In a previous post, I found a cam on the filter shaft whose position appeared to be seriously out of phase. During a print cycle, the machine rotates a cam which trips the escapement mechanism to move the carrier one column to the right. It must happen after the printing has completed, thus the timing of the cam is important. 

A filter shaft is geared to turn at the same time as the shaft for the carrier, both of which are turned by the main operational shaft when the print clutch has been tripped. The carrier shaft will lock the ball in its tilt and rotate position, swing it forward with appropriate velocity and return it. This shaft also lifts the ribbon so that it is in between the type ball and the paper on the platen. The filter shaft is used to release the keyboard on typewriters, as well as triggering the print escapement.

The challenge in following the maintenance documentation is the enormous variety in selectric mechanisms, even when it is a print only device like the 1053 on the IBM 1130 console. The 1053 is also used as part of the 1052 operator console for a S/360 mainframe, but its implementation is very different. Other 1053 are used as output log printers on mainframe systems, having their own implementations.

As one example of the variety of implementations, just considering the print only devices, consider the tab function. The 1053 on the IBM 1130 does have tab settings and a tab movement function, but the other print only 1053 such as the mainframe models do not include any tab oriented hardware. 

Because of this, the diagrams and procedures are not highly specific to the model you are repairing and as  a result mistakes are easy to make. I saw a 1053 document that showed the print escapement cam at the side of the machine on the far end of the filter shaft. I have a cam on the side and that is what I adjusted. 

Well, it turns out that the print escapement cam is inside, not as far along the filter shaft, while the cam I was adjusting provides a function that is not used on other selectric models. The outside cam is a lock which stops the shift mechanism from rotating the ball between upper case and lower case sides, during a print cycle. Thus the low point of the cam is when the interlock is in place, freezing the shift mechanism. On the print escapement cam, the low point of the cam is when it is not driving an escapement. 

Thus, at the time that a print cycle is not happening, the idle time, the escapement cam should be at its low point so as to not trigger movement, while the shift interlock cam should be at its high point to release the interlock permitting the operator to shift back and forth between UC and LC. I corrected the adjustment for shift interlock, undoing my error.


I also got the index (move down a line) and carrier return mechanisms to trigger properly. There are five functions that can be triggered, releasing a clutch on the operational shaft allowing motor power to drive the function. These are space, tab, carrier return, index and backspace. The 1130's console has three buttons on the front which can trigger the tab, space and CR functions.

In addition, five solenoids are implemented to trigger each of the five functions. The only way to move the paper up is to trigger index with the solenoid; similarly only the solenoid can trigger a backspace to move one column to the left of the current position. 

I verified that all of these solenoids are triggering the clutches to drive the function. I adjusted most of them to work properly. I am still fine tuning the backspace and the space functions while the remainder are in good shape already. 


Another collector had mailed two boxes of punched cards to me containing various historical programs for the IBM 1620 computer. It only took a fraction of an hour to unbox these and read all 4000 cards into separate files for each logical deck. 

Thursday, October 26, 2023

Reading and archiving a box of cards for an IBM 1620


I have two Documation card readers with interfaces that allows me to read punched cards and create PC files with the contents. My best one reads at 1000 cards per minute, which means that even with reloading the hopper it takes about three minutes to read an entire box (2000 cards are in a box). I built an interface into the reader with a USB cable that plugs into other computers. Programs on the computer can issue a read command and collect the 12 rows x 80 columns of data as the card is read. 

Reader processing card decks to a capture program on PC

I read the decks twice and digitally compare the contents to check for errors that might have occurred during reading. I also ask the collector or other expert on the computer system to work with the digitized deck to check for the very unlikely chance that the same error happens with the same card in the deck on both runs through the reader. 

Because computer systems often use multiple encodings on punched cards, I read all decks in a lossless binary format that records the holes in all twelve rows for each card column, rather than converting to the Hollerith characters that are the most common encoding. 

For example, the IBM 1130 does use Hollerith for most cards, but it has several binary formats that can be employed. In addition, data cards for applications are free to set up any encoding they wish, thus a card may intermix Hollerith characters in some columns with other encodings in different columns. 

One method uses twelve rows of one column plus four of the second column for a single 16 bit binary word, then continues with the remaining eight bits in the second column plus the first eight rows of the third column for a second 1130 word. Finally, the last four rows of the third column and all twelve rows of the fourth column are combined to form the third 1130 word. This uses four columns per three 1130 words. Another format uses two columns per 1130 word, wasting four rows of the pair thus is a less dense storage format.  

By recording the cards in the lossless format digitally, the recipient is free to interpret any column of any card as justified. Once can interpret as Hollerith and then store an ASCII equivalent character in a file. Some of the glyphs used with IBM systems don't exist in ASCII but there are Unicode representations that can be used, as long as the programs that manipulate the files are Unicode capable. On the 1130, for instance, IBM uses the cents sign and a logical not character, which do not exist in ASCII. Record, group and word marks are other glyphs that were used in older IBM systems which do not exist in ASCII. 


A box arrived with decks which included the Algol and the Snobol languages for the 1620 system. These cards mostly had sequence numbers in the last columns of each card which serves as yet another validation of correct sequencing and accurate reading. We did discovers a few sections that were misplaced in the box, for example a 42 card program that was stuck in the middle of another longer deck, but that could be corrected digitally. 


A different collector is sending me two boxes, which contain quite a few decks of various sizes. When those arrive I will read them and send them back to the collector. Often the digitized files are also shared with other enthusiasts allowing them to run the newly captures programs on simulated computers or their own restored mainframes. 

Wednesday, October 25, 2023

1053 has many adjustments quite far from correct, working through each section of the machine


There is a cam that rotates for each print cycle, so that at the end of typing a character on the paper, the carrier will advance one column. The cam should have been adjusted so that the linkage is at the low point on the cam when not printing - this ensures the correct timing between typing a character and spacing afterwards. 

When I looked at the machine, the cam was almost halfway out of phase, pulling on the escapement link while at rest. This would space while the typeball was flying, producing smeared and improperly spaced characters on the paper. I rotated the cam to its proper setting, thus achieving the proper spacing at the end of each print cycle.

Rest position at low point of the escapement cam


When the tab button is pressed, it releases a clutch on the main shaft which spins the clutch one half turn. The clutch pulls on a turnbuckle link which rotates the tab bar. The bar should latch the escapement lever out of the escapement rack to start the carrier moving to the right. However, if the bar isn't rotated enough then the mechanism does not latch. The symptom is a short movement but not sustained tab movement. 

Since the carrier was only moving a couple of columns regardless of the tab settings, I began checking the mechanism that rotates the tab bar. This is spring loaded to sit at a stop position and be rotated when the link pulls. I saw that the spring was unable to pull the mechanism all the way up to the stop position and the result was inadequate rotation of the tab bar.

I realized that the turnbuckle link was way too short. Once I adjusted it, starting a tab operation fully latches the escapement and the carrier moves to the right until it encounters a tab disk in the set position, which releases the escapement latch. 

Spring pulls tab lever fully up to the stop position

Turnbuckle link that was lengthened


The 1053 has two different mechanisms that activate the same escapement bar. One is driven by the print cycle cam as discussed above, while the other is activated when the clutch on the main shaft is triggered to drive a space operation. The Space button on the front panel and the space solenoid both use this second escapement method.

Unfortunately, the carrier moves about three columns every time this is activated, rather than the single column that occurs with the print escapement. I had to diagnose the cause for this - obviously some adjustment - and fix it. 

Monday, October 23, 2023

Rotate spring tension set correctly, tab setting sliders loosened as I continue to work on the 1053 console printer


I managed to find a solution to the conflict between lights, my eyes and the tools, so that I could see and maneuver the rotate spring and its detent. I relieved tension on the spring and then carefully added it back in until I got to the desired range of rotate tape tension. 

The tension is measured by setting up the machine with the type element (ball) on the lower case side, commanding a character with a -5 rotation and hand cranking this until the rotate pulley on the right is just about to hit a stop pad that limits the pulley lever arm travel. With this condition set up, an IBM spring scale pushes against the pulley lever arm and measures the force required to move the arm outwards. 

This force is the target spring tension of 1 7/8 to 2 1/2 pounds. I found a setting that produced 2 1/4 pounds of force, right in the desired range. To verify this is good, we also check at +5 rotate character from the upper case side of the ball.

Tripping a solenoid on the side of the machine causes the pulley lever arm to move outwards to the right, which pulls the ball around so that the upper case side faces the platen and paper. The +5 rotate character was triggered and hand cranked to the point where I could again measure the force on the pulley lever arm. We still had 2 1/4 pounds of force, confirming that the rotate tension setting is correct. 


The tab setting sliders are discs that fit inside slits on the long tab cylinder, one slit per column that the carrier can reach. The disc rotates so that the two projections which stick outside of the tab cylinder diameter are either rotated backwards to the rear of the typewriter or partly forward. The forward position puts a projection right in line with the escapement mechanism on the carrier. The carrier strikes the projection and releases the latched tab condition allowing the escapement pawl to enter the rack and stop the carrier at this position. 

Quite a bit of corrosion has occurred inside the slits and on the faces of the discs, which froze some in place and made them all very hard to rotate. Using my clock oil and patiently moving each one back and forth many times, I got most of them to move freely. I still have a few that are stiff but with time and more manipulation I expect them to all work properly.

I verified the gang clear function, where as the carrier is pulled right to left during a carrier return operation, if the Tab Clear lever is activated simultaneously, a wedge on the front of the carrier will force up any tab discs that are rotated into the 'set' position. This clears all tabs in one operation, instead of requiring the user to repetitively tab to each set position and then move the Tab Clear lever. 


IBM implemented a mechanism called Whiffletree Linkage to select the amount of movement of the tilt and the rotate tapes required to move the ball to print the intended character  The heart of this mechanism is different lengths from pivot points to the activation levers for each 'bit' of selection. 

Tilt is easier to explain since it has only four possible positions. A horizontal bar has two levers dangling from its ends. One is twice as far from the horizontal bar pivot as the other lever. Thus, pulling down on the far lever produces one unit of movement, pulling down on the nearer lever creates exactly twice as much movement of the tape, and pulling both down adds together the movement to pull the tape three times as much as the far lever alone. 


Rotate requires five positions in one direction and five positions in the other plus no rotation, thus eleven possible rotary positions of the ball. The mechanism has a negative rotation link which reverses the direction of the movement plus four levers to select one of the six positions in a direction from no movement to rotating five positions. 

As the typewriter sits right now, it rotates the ball less than one character position so that a +5 or -5 character request only produces a movement to the +4 or -4 character on the actual ball. I will be working through the adjustments that must be made, in the proper sequence, to cause the ball to rotate properly.

The first sets of adjustments are setting the rotate spring tension and setting the left side rotate pulley lever to be exactly vertical when the ball is set to the zero rotation position. Immediately afterwards, I had to deal with the failure of the vertically hanging levers from the Whiffletree to restore themselves under the bail that will pull the levers which select the amount of tilt or rotate movement. 

I don't know if the improper position of the levers is part of the inadequate rotation of the ball but the adjustment needs to be made so that they do restore. When a lever is selected by the solenoid, it is pulled away from the bail so that that lever is NOT pulled down. It should restore under the bail so that the next request for a character where the solenoid is not driven should have the lever pulled down. Failure to restore may result in mis-selection of print characters at speed, thus this must be corrected.

Metal tabs above the top pivot of the vertical levers are bent downwards until the bottom end of the lever will restore under the bail. These are called stops. There is no direct way to reach and bend those tabs while the Whiffletree mechanism is in place, but I don't want to disassemble everything. I will figure out a method to adjust the stops and do it. 


I noticed that at the end of the day today, the transport pulley has moved outwards away from the scribed line, indicating insufficient tab cord tension. It seems obvious that the CR drum screws are not holding the drum on the shaft sufficiently, I was worried about the amount of torque I had to apply last time and it still didn't hold. 

My guess is that sludge is in the threads of the drum hole and on the screws. I will try to clean them out thoroughly and reinstall the drum. I may have to use some Loctite Threadlocker to hold them in place so they don't loosen up on their own, but only when I am certain that the screws are holding the drum firmly to the shaft. 

Sunday, October 22, 2023

Tab and carrier return cords installed at proper tension


It took a few more iterations than I expected, in part because the drum would slip if I didn't really tighten the screws down quite firmly. It felt as if I was on the edge of material failure on the screw when I attained the final tightness that left the transport pulley at the target position .

Left edge of slider right on scribed line


Tab positions are controlled by a long cylinder running from left to right behind the carrier rails, with a rotating slider for each of the columns across the page. Moving the slider in one direction allowed the carrier to sail past it unimpeded during a tab operation, while placing the slider in the other direction would trip a latch on the carrier to stop the movement at this column. 

Pushing the Tab Set or Tab Clear button on a typewriter (an up/down toggle switch on the 1053), causes the slider at the current column position to be moved to either the set or the clear position. As a convenience, when doing a carrier return, if the Tab Clear is held down then the carrier resets the sliders on all columns as it returns past them. 

These sliders were stuck in place by solidified lubricants, requiring me to flush them out with clock oil and work the sliders back and forth until they moved freely. With that done, the tab operation could work as intended, moving the carrier right to the next column that had its slider set. 

Tab sliders move to set or clear positions


The rear of the carrier has a set of levers that are connected in a complex way. Two of them have pawls that engage in the teeth of their associated racks.  Another will force both of the pawls out during the carrier return and the tab movements. 

The space rack is what holds the carrier at its current column against the pressure of the mainspring and tab cord seeking to pull it rightward. The escapement lever can pivot its pawl out of the rack, the carrier begins moving, and then a spring pulls the pawl back into the next tooth of the rack. This moves the carrier a single column to the right. 

This lever is moved by a long bar running just behind the carrier, which pivots during the end of the a character print cycle to cause a one column advance. It is also pivoted by the operation of one of the two operation clutches, when the space button is pushed on the front of the 1053 or when the space solenoid is activated. The button or solenoid trips a clutch, rotating a cam one half rotation during which the cam moves levers that, in the case of a space function, pivots that bar that moves the escapement lever.

A second rack is offset a bit from the first and has pawls on the backspace lever that insert into the rack. If the backspace solenoid is activated, it trips the same clutch as was used for space, but the cam moves levers that engage the backspace pawl and drive the carrier back one column. The escapement pawl pops out of its rack and into the tooth one position behind. 

Finally, the escapement and backspace pawls are held out of the teeth of their racks during the long movement operations, tab or return. Another pivoting bar behind the carrier moves those levers out of the way. In the case of a tab operation, whose distance is determined only the the sliders that are in the set position, some levers and springs hold the pawls locked out of the teeth but when a set slider strikes a small projection on the carrier it releases the pawls to lock the carrier at that position. 

The escapement and backspace pawls plus tab latch levers

Some success with tab and carrier return cord installation


With the carrier return function engaged so that the drum shaft won't turn on its own, the two screws holding the CR drum to the shaft are loosened and the drum rotated enough to add a bit less than a half an inch to the net cord length. The cord would then fit over the spring loaded pulley (transport pulley) and the pulley sits at the scribed line  on the assembly to indicate proper tension. 


I loosened the two screws but the drum wouldn't turn on the shaft with hand pressure. I backed out the screws further and eventually they came fully out of the drum yet it wouldn't budge. 

Drum with screws removed

Removed screws


The from (tab) drum uses a single setscrew that tightens against a flat spot on the common shaft, but the presence of two screws on the CR drum suggested it did not have a flat spot. However, with no movement of the drum, I considered the possibility that my speculation was wrong. 

I therefore removed the entire shaft and drum assembly from the parts donor Selectric I had acquired and got the drum off to examine the shaft. The drum didn't slide off but when I used vise grips to turn it relative to the shaft, I began to turn. Apparently it was just grime that had hardened to stop the drum from turning. 

Studying shaft from donor typewriter


Once I was comfortable that this should and would rotate freely around the shaft, I carefully applied some tools to the metal hub of the CR drum and worked on moving the drum. I did get it to move, slowly at first and then with less pressure as I increased the distance it had moved. 

This allowed me to move the carrier and even up the pressure on the tab and CR cords. The cord could then be pulled over the transport (spring loaded) pulley with the assembly just about at the scribed line. I tried moving the carrier in both carrier return and tab directions with hand cranking and it appeared to be working correctly. Clearly this method is the key to getting everything perfect.


Because I hadn't replaced and tightened the screws while I was checking the cord tension and positioning, the force of movement rotated the CR drum a bit more resulting in the transport pulley sitting too far out from the frame. There is not quite enough tension now.

Cord is a bit too loose

All this means, however, is that I have to move the CR drum back in the other direction, tighten down the screws and then verify the tension. It may need a bit of iteration but I am certain to get the tension just right using the new method. That will be my next task when I return to the workshop, then I can move on to setting the rotate spring to its proper tension. 

Friday, October 20, 2023

Found a new approach to get the tab/return cord tension adjusted


These cords hook onto the carrier of the typewriter and run in opposite directions, providing the force to move the carrier left or right. The reverse direction around pulleys on the sides of the machine and then are wound around drums. These drums are on the same shaft hooked to the mainspring. 

They hook onto attachment points on the carrier and at the start of spiral grooves on each drum. As the mainspring shaft rotates, one drum winds in cord while the other drum plays out the same amount. Turning one direction, the carrier is pulled to the left by winding on the carrier return drum while cord is released by the tab drum. The other direction winds the tab cord on its drum while the carrier return drum releases some of the carrier return cord.

One of the pulleys on the side of the machine is spring loaded, in order to maintain a target tension on the cords. A scribed line on that assembly marks the ideal position of the spring loaded pulley when the cords are at the proper tension. 

To keep the cord from popping off its drum, each drum must have about one wind of cord when the carrier is at its extreme position - left side of the machine for the tab drum and right side for the carrier return drum. With the cords attached to the drums with the desired one wind of cord on one and the other drum wrapped as many turns as needed to keep that cord tight, the tab cord should fit around the spring loaded pulley and sit at the scribed line.


The process of installing the cords puts the carrier return cord the carrier, routes it around pulleys on the left side of the machine and hooks it to the attachment point  of the CR drum. Latching in a carrier return operation causes the CR drum to wind up the cord as you manually crank the machine, pulling the carrier to the left side of the machine. 

Each spiral of the drum pulls the cord by a specific amount (pi times the diameter of the bottom of the spiral groove on the drum) until carrier reaches the left margin (side) of the machine. When the carrier is at the far right margin/side of the machine, there would still be a bit of cord wound around the CR drum thus the cord won't pop off.

Next the tab cord is hooked to the attachment point of the tab drum, wound around it once and then routed around the side pulleys until it is hooked to the right side of the carrier. Each turn of the tab drum pulls the cords the same amount, pi times the diameter of the groove bottom on the drum spiral. 

What this means is that the attachment point position of the two drums determines the start of the cord and then each rotation of a drum pulls up pi times the groove diameter of cord. The attachment point position on the drum can be anywhere in a 360 degree rotation, thus the angle where the attachment point sits when the cord is attached can shorten the cord by up to pi*D. 

If the drum's spiral groove bottom is one inch in diameter, to simplify the math, then the cord length is from 0 up to 3.1415" shorter, determined by the angle of that attachment point. This is important since the cords don't have a fixed net length, it is determined by the attachment point angles. 

When I installed the two cords per the various installation instructions, I end up with the tab cord net length too short by about 3/4 of an inch or it is too long when hooked to the tab drum attachment point without any turns wound on the drum as the carrier is all the way on the left side of the typewriter. 

I can compensate for the overly long cord by tying knots but the lack of any winds on the tab drum results in the cord popping off during a carrier return operation. Thus I need one wind of the cord on the drum, producing the deficit of about 3/4 inch. 


I have several manuals describing the adjustment procedures for the I/O Selectric (and regular Selectric). Every one, including the documents that came with the IBM 1130 system, skip this key adjustment. When they talk about adjusting cord tension/length they only cite the ability to tie knots in the cord to shorten it. I then found one manual online with this figure that offered a hint.

This does not show the two screws for adjustment, nor mention rotation of the drum. The right hand transport pulley is the one that I call the spring loaded pulley. In retrospect, I see that this comment means intends the mechanic to loosen the two screws on the CR drum, turn it to set the position of the 'transport pulley', then tighten them up. 

Setting a  new rotary angle for the CR drum effectively can shorten that cord by up to 3.1415" but the target is to shorten it by the missing 3/4" which simultaneously moves the attachment point of the tab drum enough to have one wind of cord on the drum with sufficient space to fit onto the spring loaded pulley. 


The front drum (tab drum) is affixed to the shaft with a single small setscrew. The documents all warn that this setscrew fits onto a flattened section of the shaft thus you can't turn the tab drum to adjust the cord length. It only fits at one rotary position relative to the shaft. 

Tab drum

Otherwise this would be the obvious pulley to try to adjust, as it is the tab cord whose length over the spring loaded pulley is the subject of adjustment. Due to its construction, however, that drum cannot be rotated around the shaft. Instead we have to adjust the CR drum, which changes where the tab drum stops when the carrier is at the full left position. 


The rear (carrier return) drum has two screws placed at ninety degree positions around the shaft, with nut heads to make it easy to turn with a wrench or nutdriver. These anchor the drum to the shaft and thus don't depend on flat spots as the tab drum does. 

Different model drum 

I couldn't find a good picture of the CR drum, which looks very much like the tab drum above but has the nut head screws I mentioned. This picture from a different Selectric model has setscrews instead of the nut head type but you can see the same basic adjustment scheme with two screws at ninety degree angles. 

That is what the terse comment in the IBM manual above refers to when it says to 'adjust carrier return drum until . . .  right hand transport pulley is clearing side frame . . .' as we want to cause the tab drum attach point to have moved. 


The mainspring can remain wound up, under tension, because the gears and clutches at the front of the machine hold the tab drum from movement when carrier return is activated, thus I can loosen the carrier return drum without the spring spinning around.

Loosening the two screws with a wrench, I can spin the carrier return drum on its shaft, letting out a bit of cord until the tab cord side would be in the approximate position to sit at the scribed line of the spring loaded pulley that we wish it to attain. Once tightened up, I can pull the tab cord over the spring loaded pulley and verify the cord tension. 

Wednesday, October 18, 2023

Getting close on tab cord and rotate spring tasks


I used the method from Phoenix Typewriters I watched on YouTube and carefully loaded the cords and wound the mainspring. When it was done I was left with a cord attached but too tight to fit over the spring loaded pulley on the right side. It is just a touch too short - if I had perhaps 3/8" to 1/2" more length then the spring loaded pulley would sit at the scribed line that shows perfect positioning. 

Tab cord attached with one loop around pulley

Cord too tight to fit on spring loaded pulley in normal position

This is the result with one loop wound around the tab pulley. I can add knots to shorten the tab cord but then it attaches without any loops around the tab pulley; that is likely to result in the cord popping off the pulley when the carrier reaches the left margin. 

Will study this carefully and see if I can figure out a fix that doesn't require manufacturing a new set of tab and carrier return cords to get the correct lengths. 


Finally I found an opening where I could see the two objects I need to manipulate to release some rotate spring tension. The rotate spring is a disk shape that sits at the bottom of the shaft which holds the typeball. There are notches around the periphery of the spring and a detent that extends out to catch the nearest notch. This keeps the spring housing from rotating.

To add tension, a screwdriver or hook pulls the spring housing around, with one notch slipping out of the detent and the next notch clicking into place. To release, however, one has to simultaneously manipulate both the detent and a notch on the spring housing.

I will have to pull the detent away from the spring housing disk, freeing the notch, while the other hand controls the unwinding of the housing so that it only moves a bit before I release the detect. Then, the detent will have clicked into the notch prior to the one it had been holding. I do this repetitively until I measure correct spring tension of 2 to 2 1/2 pounds force at the rotate arm. 


The gap through which I can see the rotate spring housing and the detent is small. The parts I have to touch are a bit deep inside the gap as well. This triggers the battle among three necessities to do this work. First, I need a bright light at the proper angle to shine down and illuminate the parts to be manipulated. Second, my eyes have to be over the gap so that I can see the parts. Third, two tools have to fit into the gap, one to control left to right movement of a notch on the spring housing and another to move the detent forwards to release it. These have to be fairly small tools because of the limited space.

My challenge is the conflict  between those three elements. The light has to be at the correct angle to illuminate, but that is essentially the same angle that my eye needs in order to see. Then the two tools and my hands will block both the light and my eyesight. 

I have a couple of USB optical inspection cameras, one of which might be useful if I can suspend it to give me the view from a PC screen instead of needing my eyes in place. If I can then work out a light placement that shines around the camera, the remaining issue is tool access and movement. I expect this to be a learning experience as I try different placements for everything. 

Monday, October 16, 2023

Discovered broken mainspring during the Tab and Carrier Return cord work


The key to this new method is that I don't have to shorten the tab cord with a knot. That dramatically reduces the risk of the cord popping off the pulley as it did before. This method comes from a Phoenix Typewriter YouTube video I just watched.

First step, with all cords disconnected from drums, is to latch in carrier return and hand cycle until the mainspring stops at full tightness. The next step would be to release about seven turns before attaching cords and the rest. 

The mainspring never tightened past a certain point, which indicated that it was broken internally. That explains some of the funky behavior I saw during my prior attempts to attach the cords 


The mainspring on the Selectric 1 I bought as a parts donor was in good shape, so I moved it over. I then opened the original mainspring and confirmed that it had broken inside. 

Broken spring

Donor machine replacement

Next session in the workshop I will wind it up then go through the Phoenix Typewriter procedure to try to get my carrier return and tab cords properly installed. Hopefully that will be successful so that I can move on to fixing the excessive tension on the Rotate spring. 

Sunday, October 15, 2023

Drama and defeat in the battle of the tab cord attachment


When I had attached the tab cord to the drum and the carrier, it only needed to be pulled out around the spring loaded pulley that will maintain tension. The strength of the springs on that pulley don't allow simply pushing the pulley inwards while manipulating the cord. 

I ended up removing the pulley assembly, fitting the cord on it and then twisting it up into place in order to reinsert the screw attaching the assembly to the typewriter. There it was - a set of cords attached and at proper tension. The carrier was about 1/5th of the way to the right, which was the position that allowed me to attach the tab cord, maneuver it to get a second loop around the drum, and attach it all prior to the spring loaded pulley dance. 


I latched in a carrier return to pull the carrier to the left edge of the machine and to wind some tension into the mainspring. Everything moved well until I reached the edge and tried to release the carrier return clutch. The machine did not unlatch, it strained pulling the carrier against column 1 and kept turning the tab cord drum so that the end of the cord was barely in the notch with no spare cord. 


As I wrestled with the machine trying to get it release the carrier return clutch and stop turning everything the wrong way, I heard a pop and the end of the tab cord came off the drum. Time to start over and try this again. There must be some secret to doing this, but none of the IBM manuals nor the YouTube videos address it, instead presenting the idealized process where it all just fits together and works. 


I did some work building my new vacuum tube curve tracer, a project that I originally cobbled together some years ago based on Ronald Dekker's uTracer design. Ronald works at Phillips Research and definitely knows vacuum tubes. This device connects to software on a PC that gives all the curves and results with a very nicely built GUI. 

The uTracer had a weakness in how it drove the filament voltage which was corrected by a clever design from Stephan Lafferty that adds a very accurate filament/heater power supply. I recently completed the heater part of the project and decided to improve the build and esthetics from the quick and dirty version I made years ago.

I cut a new front panel and made a decal labeling the various controls and sockets, unsoldered everything from the old panel and began construction. I lost one of the knobs so I will be replacing all ten of the bottom knobs with a new type of knob, as soon as the order arrives. I installed all the controls and sockets today and began soldering everything up. 

Each of the nine possible pins of a tube socket as well as the cap electrode can be switched to one of six roles - cathode, control grid, screen grid, anode, or either end of the filament supply. That accounts for the ten knobs at the bottom. The rotary knob at the top sets the filament voltage to 5, 6.3 or 12.6V but allows for an external supply if a tube has an unusual heater voltage requirement. 

There are four sockets, for 7 pin and 9 pin miniature tubes, octal tubes and loctal tubes. Pin straighteners are on the panel to ensure that the pins don't bend or snap while being handled. I can make adapters that plug into the octal socket to accommodate rarer tube types including nuvistor as well as the older tubes like a 4 pin radio tube. 

I also did some organizing of the workshop, collecting items into containers and labeling them. This makes the shop neater and more open but also helps me find what I need much faster than the chaos of before. 

Friday, October 13, 2023

The tricky installation of the tab and carrier return cords, as well as challenges loosening the rotate spring tension


There are two string like cords in a Selectric typewriter mechanism. One hooks to the left side of the carrier, able to pull the carrier to the left. The other cord hooks to the right side of the carrier and pulls it towards the right. Teeth fitting into racks hold the carrier in position against the rightward pull, allowing it to move one step during a space or to move freely during a tab until it strikes a tab stop that is set at some column. 


The carrier return cord is routed leftwards from the carrier and over a pair of pulleys on the left which reverse the direction of the cord and direct it behind the racks. It is wound around a drum at the rear of the machine - that drum is on a common shaft with a mainspring and a drum that sits forward of the spring. The rear drum winds up the carrier return cord as the carrier is moved to the left, feeding the cord out when the carrier is pulled to the left so that the return cord remains under steady tension. 

The tab cord is routed to the right side of the machine, changes direction over a special spring loaded pulley and is then wound around the drum in front of the mainspring. The mainspring will be wound up by the process of a carrier return, storing up energy necessary to pull the carrier rightward. The drum winds up the cord as the carrier is pulled rightward during spacing and tab operations, feeding out the cord during leftward (backspace and carrier return) operations. 


The source of power to move the carrier to the right is the release of energy stored by winding up the mainspring. This winds as the common shaft rotates in one direction and seeks to rotate the shaft in the other direction unless the carrier is held in position, for example with a tooth in the escapement rack. The spring gains energy while the carrier is pulled leftwards during a return and gives it up to move the carrier rightward. IBM refers to this as negative energy for some reason but it is just the potential energy in the wound up spring that powers rightward movement. 


The motor of a Selectric is always running, spinning the operational shaft but that shaft isn't coupled to anything else unless a clutch is activated. This is what IBM refers to as positive power in their training and documentation. In order to pull the carrier left in a return operation, the clutch connects the operational shaft to the common shaft with the cord drums and mainspring, turning it to simultaneously feed out tab cord, pull in carrier return cord, and wind up the spring. The power comes from the motor to make the movement and to restore energy into the mainspring. 


Since the cords can stretch over time, a spring loaded pulley is built into the right side of the Selectric. The pulley can move left or right but has strong spring tension rightward. This holds the cords in the proper tension and automatically adjusts to stretching, within the limits of its range of motion. 


The simple sounding theory for installing the cords is much more challenging to put into practice, the issue being getting the cords to be the right length and on the drums correctly, in addition to which setting the mainspring at its proper tension. 

The carrier return cord is hooked to the rear drum, threaded around the pulleys and attached to the left side of the carrier, while the carrier is sitting in its rightmost position. 

The carrier return mechanism is activated so that as you turn the operational shaft manually the rear drum takes up the cord and pulls the carrier leftward. Proceeding carefully so as to keep the cord winding on the correct spiral grooves of the drum, you move the carrier all the way to the left. 

Next one should attach the tab cord to the front drum, thread it around the spring loaded pulley and attach it to the right side of the carrier. Here there are challenges in real life. The drum is usually turned so that the attachment point is downward and away, not convenient to hook up a cord. The spring tension of the pulley will make it almost impossible to hook the cord on, so you really leave the cord off that pulley, hook to the carrier and then force the pulley leftward while pulling the cord over it. Alas, the cord may be too long so that the spring loaded pulley can't move rightward enough to put on tension. 

If the cord is hooked to the front drum and engaged in the spring loaded pulley with proper tension, one then has to wind up the mainspring to appropriate tension. If you do all this, the carrier is ready to move left and right, handling the carrier return, space, backspace and tab operations properly.

When I have the carrier full left but the front drum mount point is inaccessible, I need to move the carrier a bit to the right until the drum rotates. Unless you are very careful looking both at the front and back of the machine, you can loosen the carrier return cord making a jumble on the rear drum. 

I had to tie several knots in the cord next to the hook that connects to the right side of the carrier, to shorten the cord appropriately. I must then tension the mainspring by winding it nine or ten turns. If all went well, I should be able to space the carrier all the way to the right. During this movement I have to watch that the tab cord winds properly around the front drum. 

I have failed multiple times just as I am moving the carrier a bit to the right or trying to connect the tab cord to the front drum. This is very tricky, as moving the shaft the wrong way loosens cords which then scramble up on a drum. 


Inside the carrier there is a vertical rotating shaft that the type ball spins on. It has a spring underneath that provides power so that when the metal rotate cord is loosened, the rotate spring takes up that length by crisply turning the shaft. It has to move fast enough to get into position during typing. However, if it is too tight, then it restricts the range of rotation. This is the cause, I believe, of the failure of this typewriter to rotate to either the +5 or the -5 positions. 

This is checked using an IBM spring scale that pushes against the rotate tape pulley on the right side. One sets up a +5 character, hand cycles the machine halfway through a print operation so the rotate tape is appropriately tensioned, then push on the pulley and see 2 to 2.5 pounds of force. My spring is offscale beyond 3 pounds right now 

Adding tension to the rotation spring is easy - there are notches around its perimeter that you can see and reach from the top of the machine. Pushing it one way will turn it to click into the next notch, adding tension. However, releasing some pressure requires simultaneously holding it steady by the notch and also pulling on a detent spring to let it rotate the other way. I can't even see this detent, much less figure out a way to get a tool in to move it.

Assuming I find a way that I can pull on the detent while also having another tool control a slow rotation of the spring to release some energy, I can remove tension until the scale shows me the target force of 2 to 2.5 pounds. This is challenging which is why I have spent quite a few hours on the 1053 just trying to deal with the rotate spring; then there is the time fighting to get the tab and carrier return cords properly attached. 

Thursday, October 12, 2023

Cover in place - could fine tune the mounting hardware but acceptable already


The mechanism has a groove on the bottom mounts, allowing the cover to be placed onto the raised ridge inside the IBM 1130 display box. On the two sides are mounts with a rotating lever to either hold the cover behind the raised side ridge or allowing the cover to tilt out if the lever is oriented vertically. 

The lever has detents that lock hold it either vertically or sideways to extend behind the ridge. A spring holds the side screw heads outward, which pulls the lever against its stop plate inside so the lever locks into one of two orientations, vertical or sideways. To operate the cover, the screw is pushed forward against the cover, moving the lever out of its lock, rotated ninety degrees to its intended orientation and released. 

The change I anticipate making is to swap the screws on the sides with longer versions that allow me to install a locking nut on the inside end. The lever has a nut epoxied to the part but the screw therefore not only rotates the part but loosens or tightens. Using a second nut to jam against the first will keep the nut purely rotating with the screw head rather than having the screw threads move in or out.

Wednesday, October 11, 2023

Put together two designs and sent the boards off to be fabbed; challenge removing typeball from 1053 for more adjustments


The quick way I implemented the console loader was using two eight relay boards and one four relay board connected to an Arduino. The Console Entry Switches (CES) on the front panel of the typewriter printer are wired to the relays and the other side goes through a resistor to ground. Then there are two buttons, Prog Start and Load IAR, which are wired to three more relays. 

By activating one relay the power is removed from the existing Prog Start switch. The user turns the rotary mode control switch on the 1130 to Load and then uses a terminal program to interact with the Arduino. The text in the file then causes the Arduino to set the CES and push either Load IAR or Prog Start in order to set memory addresses and store contents. 

The issue is one of space and elegance. The relay boards take room under the cover of the 1130, in front of the keyboard, plus we need an additional box elsewhere to hold the Arduino. I designed a board to use optoisolators to replace the relays, that board mounts atop the Arduino and we only need to find a space for that smaller stack inside the console. I sent this off to the fab as well, since I already have the optoisolators and the Arduino. 


The Cape Canaveral Space Force Museum has several locations, one of which is outside the security perimeter thus readily accessible to the general public. It has a number of small LCD displays that run various videos discussing activities. These are older units and are behaving very badly. I suspect some kind of corruption to the files as they have repeatedly lost power over the years. 

I decided to whip up a Raspberry Pi based solution that can drive any HDMI monitor as a replacement. It makes use of the Pi Presents open source application to animate such displays. There are a few challenges that aren't properly addressed by the Pi hardware and application. 

Any time power fails, the Linux system running on the Raspberry Pi can leave the file system in a corrupted state since it didn't shut down gracefully. The Pi Presents software can schedule automatic start and shutdown of the displays, but it needs a persistent clock or an internet connection to know the current time. The building does not have internet connectivity. Finally, the staff needs an easy way to start these up for an unscheduled event and to shut them down when leaving at the end of that event. 

I whipped up a circuit that will be built as a 'PI Hat', a board that fits above the Raspberry Pi and plugs into the 40 pin connector. It will provide a real time clock with battery protection so that the system always knows the correct time. It will feature a supercapacitor based system that provides 90 seconds or more of power when the input power drops, plus sends a shutdown signal to Linux, allowing the system to gracefully close all file systems. It has an autostart feature when power comes back on, a start button for manual startup, and a shutdown button that triggers a Linux shutdown. 

This was completed and sent off to the fab for production. It mostly uses surface mount components for compactness. The supercapacitor system that charges the capacitors and then uses them to produce 5V for the machine during power outages is built around a MAX38889 chip. The real time clock is built around a DS3231 chip and a CR2032 battery. The battery needs to be replaced every two years and the capacitors should be replaced every eight years. 


When IBM first introduced the Selectric typewriter, the typeballs had a plastic lever and cap to remove them from the typewriter, but they soon switched over to a design that had a knurled metal cylinder that the lever was molded onto. The newer construction produced balls that tend to break so that the lever snaps and the element won't detach from the typewriter. The metal cylinder is left on the cap but can't be turned without a lever.

Inside the cap is a strong metal spring that has two arms which snap shut into a groove on the spindle of the typewriter. The metal cylinder has ramped ends that will push the two arms apart so that the ball can be pulled up and off. The lever would cause the cylinder to rotate, that is until it snapped off. This is a very very common failure of these early type elements. IBM eventually went back to all plastic mechanisms which don't break. 

All of the 1053 console printers and most other I/O Selectric devices use the typeballs with metal cylinders, meaning on most of them the ball is stuck on the unit. This doesn't cause a problem in operation but it would be nice to remove the element to clean off built up ink and it is important to make certain adjustments with the ball out of the way. 

The space through the plastic cap to the ends of  the spring arms is very tight, thus ordinary tools like snap ring pliers can't fit in. I will work out a way with my existing tools and perhaps the hardware store to remove the ball for the current restoration, but I want to accomplish two things longer term. First, I want to modify the balls to have a working removal lever. Second, I want to fabricate a tool to easily remove these elements with broken levers. 

Friday, October 6, 2023

Still working on 1053 character selection after a busy day at Cape Canaveral


A tour van was scheduled to visit Hangar C and the main museum at LC26, but the original staff who would have met them were unable to work it. I was called to head over, open up the buildings and deal with the visitors. I left around 8:30 this morning and wrapped up the tour support by lunchtime.


United Launch Alliance had an Atlas V rocket scheduled to launch the first two Kuiper internet satellites to allow them to be verified in space. Kuiper is the constellation of birds that Jeff Bezo's Blue Origin plans to put into orbit in order to offer a competitive satellite internet service.  It was scheduled to launch at 2PM, so I had time to stop by the base cafe for a quick lunch and then police the visitors watching the launch from ITL road. All in all, I didn't bet back to the shop until after 3:30PM because of all the above. 


Having finished both sets of mounts and pivot mechanisms for the rear cover of the 1130 display pedestal, I did a test fit and wasn't happy with the operation of the latch. I switched to a longer bolt that gives more room for the spring loaded movement to release and turn the pivot.  


The 1053 console printer is having issues moving the typeball to the -5 position. The ball stops turning around -4, when the detents lock the ball into its incorrect position for typing. Something is maladjusted but I am not yet certain of the culprit. 

When this is combined with the failure of the positive rotation latches to return under the restoring bail, I suspect there are multiple problems. I can't imagine how a Selectric mechanism got this far out of adjustment, unless someone had tried to work on it in the past and randomly changed all sorts of adjustments. 

Bottom line is that I don't understand yet why these two problems exist. I do have both my own 1053 and the parts donor Selectric to compare against, so sooner or later I will spot the critical difference(s) and then they can be corrected. 

Confession - being too reliant on black box components, my uTracer Vacuum Tube Curve Tracer heater regulation board project didn't work


A while back I built a vacuum tube curve tracer designed by Ronald Dekker which measures tubes and produces curves to compare to the spec sheets to assess tube health and performance. One weakness of this design was in its ability to drive the filaments, which is overcome by a heater regulator board design from Stephan Lafferty. 


The regulator board made use of a very accurate 2.5V reference source to precisely control the voltage of the filament supply through an opamp feedback loop, with extreme precision resistors used to set the voltage points to generate 5V, 6.3V and 12.6V output levels at up to 5A. 

It also is a four wire delivery system, meaning that there is a separate sense wire for both ground and + voltage levels. Thus any voltage drop on the supply wires to the tube socket is detected because the sense voltage is lower than the target. The heater regulator board design is controlled to drive whatever voltage is necessary to produce the exact filament voltage as seen by the sense wire. 

The buck converter used to drop the 19V incoming supply voltage to the desired filament voltage was a board sourced from eBay that was built around the XL4005 IC. This board was manufactured in China and provided 5A buck voltage regulation with either constant voltage or constant current control, but at an extremely low price, thus it was not worthwhile for Stephan to design his own converter. 

The part specified in the design of the heater regulator board was no longer available on eBay or Amazon. I found some similar boards, based on the XL4015 chip, whose specs and layout appeared to match. I chose to buy those but when I tested the overall heater regulator board, it didn't work. I lazily assumed that XL4015 was a more modern and potentially slightly cheaper chip that the makers had switched to. 

I finally switched on my brain recently and downloaded the spec sheets of the two chips, XL4005 and XL4015. Two differences were apparent - switching frequency and the set point for the regulation. 

The original chip operated at 300KHz while the newer regulator chip operated at a lower 180KHz. This might introduce some remnants into the uTracer which weren't filtered by the component values on the heater regulator board. 

The fatal difference, however, was in the set point of the chip. The XL4005 used 0.8V as the feedback level, while the newer XL4015 dropped that to 0.2V. The entire design of the heater regulator board was oriented around monitoring the filament output voltage and selecting a divider network to produce 0.8V exactly when it was on target, that being driven through the opamp to control the XL4005 board. 

I dug around once I realized this and found some different buck regulator boards that did used the XL4005. The first order I placed on Amazon disappointed as the boards came with XL4015 and the vendor had sneakily updated the item description on Amazon so that it now claimed to use XL4015. Luckily it wasn't a very high cost item so I simply dumped them in the trash.

The next try was successful, the boards were indeed built on XL4005. The modification for the heater regulator board opens the onboard feedback from a small potentiometer and instead connects the feedback pin to the opamp output. The board works perfectly. 

Thursday, October 5, 2023

Success with 3D printing of door hardware; continuing on 1053 typewriter restoration


I discovered an important setting for the printer, in addition to bed temperature, extrusion speed and extruder temperature. There is a parameter called Z Offset, which determines how high the extruder nozzle actually sits above the bed. Once the leveling is complete and the auto-leveling takes place as printing starts, the difference between the bed level determined by the leveling sensor and the tip of the nozzle is the offset.

The printer moves left and right on the X axis, forwards and back on the Y axis, while it moves up and down on the Z axis. After the auto-level completes it has a mesh of offsets from the presumed home level of Z=0, since it tests sixteen points across the bed to compensate for tilting and warping of the bed. To that we have to add the Z Offset to place the nozzle the ideal height above the bed. That is a tad less than the thickness of a sheet of printer paper, to produce the best results.

I experimentally determined the offset, set it in the software and immediately achieved successful printing of both the bottom mount and the pivoting side parts. I am delighted with the quality of the parts and can't wait to print the second set of parts and install it on the rear cover. No issues at all with adhesion, nothing fancy needed. 

Side pivot parts as they come off the printer


I discovered a broken part on the side of the 1053, the cord self-tensioner. Two cord are used, to haul the carrier to the right and to wind the mainspring when the carrier does a carriage return to the left. The cord that pulls to the right is routed around a pulley with a strong spring, called the self tensioner. The purpose of this part is to absorb slack as the cords stretch with age and usage. 

The self-tensioner part can be made with plastic, but those parts are famous for cracking with age (and abuse as it is sticking out on the right side). 

Damaged tensioner from 1053

Luckily the parts donor machine I bought had a good tensioner - one that was made with metal instead of the plastic used in the 1053s. It is stronger than the original part, therefore.

Donor part now installed on the 1053

Getting the two cords installed on the machine is trickier than I expected. I need to end up with the cords wound over the drums on the mainspring axle with just enough tension to partially compress the self-tensioner. My first attempt resulted in cords that were too short to even reach the tensioner.

This cord fit on the 1053 when it arrived, presumably, so there is some trick to installing it that I haven't yet found in the several IBM manuals covering the printer. I will keep at it until the cords are installed with a proper position on the self-tensioner. Once that is done, I can wind up the mainspring and that part of the restoration will be complete. 

I am still looking into the failure to fully reset the latches for the rotate selection at the end of a print cycle. My objective is to ensure reliable printing of characters which depends on all the settings for tilt, rotate and print shaft timing. I don't want latches that are left over from a prior print operation to cause the printing of the wrong character. 

Wednesday, October 4, 2023

3D printing mounting hardware for door, continued tweaking typewriter (1053 Console)


The main issue I had with the first attempt was that the exterior parts of the mounting hardware were large and clunky. Rather than using four T handles to secure the cover, I designed a new part for the lower edge that will sit on the bottom lip edge of the pedestal display cabinet. This new design means we only have a single visible screw head on the outside of the cover behind each of the two lower edge parts. . 

For the two side mount mechanisms that will latch the cover in place or release it, I kept the T handle for the outside but developed a set of rotating parts, spring loaded, so that the user pushes in and turns the handle 90 degrees to release the latch. Other than the 3D printed parts I will use a spring, two T handles two screws and four nuts with epoxy securing the nuts to my interior parts. 

The arm part on the left faces down onto the holder part on the right, so that the bulge in the arm will nestle into the gaps on the holder in one of two rotary positions. The holder is attached to the rear of the cover with epoxy and sits so that the edge that is closest to the hole is next to the lip edge of the display pedestal enclosure. 

Thus the arm, when the bulge is fitted into the gap opposite the lip edge, will extend over the rear of the lip edge and keep the cover from opening. Rotating so the arm bulge fits in the other gap, the arm will be rotated parallel to the lip edge and thus allowing the cover to pivot out. 

A spring sits between the T handle head of a bolt and the cover, so that it tends to pull the bolt outwards. The arm is epoxied to the nut on the end of the bolt. Thus the spring keeps the arm pulled into the holder so the bulge and gap blocks rotation. Pushing forward on the T handle against the spring allows the arm to move away from the holder and be rotated. 


I had picked up a 3D printer from a fellow computer restorer - so it is used because he owned it before but it is new to me. I brought my mounting hardware files to the shop, adjusted the printer and gave it a try printing these in ABS plastic. 

I am still having difficulty getting the printer to start the first layer reliably, but I work on it every day so eventually . . . 


There are so very many tiny parts, pivots, levers, springs and the like on a Selectric typewriter, all of which have the potential to be gummed up from stale lubricants. A good working estimate is 3,000 parts. Now that I have addressed all the larger and more obvious components, it was time to focus down on the tiny details that remain stuck.

The ribbon advance mechanism is a case in point, As the typeball is thrown forward to type a character, it should slide a plate forward which has pawls that would turn one of the two ribbon axles. The pawls as well as the plate were stuck with sludge, but with some reoiling and careful manipulation they are ready to go. 

Character selection to rotate the typeball involves four levers that are pulled down in specific patterns to cause the rotate tape to be pulled out or released inwards a given amount, ultimately turning the ball within a 180 degree arc to one of 11 positions. Simultaneously two other levers are pulled down in patterns to tilt the ball up or down to four rings of characters. 

I found that the mechanism for the R5 selection was sticky and working erratically. That is, we can either see the typeball rotate as it should in the positive direction which is what R5 selects, or by its absence cause a negative direction spurious rotation. With the same selections on the other levers, I can see either a -5 rotation or the ball remain in the idle position, but the sticky mechanism causes the R5 selection to be missed in many cases. 

I had to locate the sticking part, a tiny lever pivot deep inside the machine that is the latch which keeps R5 from activating unless the solenoid releases the latch due to an R5 selection. The latch is not being pulled back to block the R5 lever movement in spite of the spring that is attached, because of gumming in the pivot. Oil loosened the old lubricants and my tools gently rotated the pivot until it was moving freely. 

Having the rotate and tilt tapes properly installed it was time to work through the adjustments to be sure it will print well. It was going along reasonably well until I noticed that the character selection latches aren't relatching correctly. This leaves the typeball partly rotated, not back at the home position. 

This may not happen under power and only while hand cycling the machine, because I do see that the next print cycle completes the resetting before the new character is latched in. I compared it to behavior of the 1053 that came on my 1130. My typewriter does fully reset when hand cycling. 

I reattached the cords that wind up the mainspring as the carrier is pulled to the left margin by a carriage return operation, then pulls the carrier to the right for space and tab operations using the power in the spring. These are two cords that wind around drums on the same shaft as the mainspring, one side letting out the same amount as is wound up by the other drum. I have to figure out how to wind the spring and tension the cords in order to complete this task.

I also discovered that some levers used to trigger the carriage return were gummed up. After I freed them up the CR button would reliably shift the mechanism into power return. This activates a clutch to turn the mainspring shaft using the constantly rotating operational shaft, drawing the carrier to the left. When the carrier strikes the left margin setting it pushes the margin bar leftward to release the return mechanism. 

This typewriter uses is a high speed rewind feature to reduce the time to return across the line. To decelerate the carrier, there is an air piston that stops the carrier from bouncing as it comes to a stop. 

I am still hunting for suitable tape to create a replacement color shifting tape that selects between the upper and lower half of the ribbon, which is a bicolor cartridge with red and black ink. This is 46 inches long,  0.105" wide and 0.003" thick. IBM used a plastic for the tape but I suppose as long as whatever I find is flexible enough and strong enough, it will do.