Wednesday, November 29, 2023

Continued battle with tab/return cords on the 1053 console printer; installing new console loader


I secured the carrier return cord to the bottom of the carrier with a bit of tape while I was routing cord around, removing it once things were under tension. Similar tips helped with the whack-a-mole problem I had last time I worked on this. 

I put a clamp on the spring loaded pulley that adjusts the cord tension, to counteract the spring force. This permits me to route the cord and tighten it without fighting the power of that spring. 


I rotated the return drum relative to the axle as a way of taking up cord and shortening it. When I had it in the proper position I tightened down the two screws that sit 90 degrees apart to lock the return drum to the rest of the mechanism. I removed the clamp and checked the cord tension, but I saw the return drum move on its own a few times, releasing too much tension.

I reset the position and tried to tighten the screws a bit more firmly. One of them was spinning without ever feeling tight and the other initially felt tight then just fell right out! When I looked at the screws I could see that the threaded hole was stripping and releasing bits of aluminum. 

This won't work. I looked back at the other assembly that I had removed, the one where the drum was almost frozen on the axle and wouldn't rotate with the screws loosened. I had done a swap with parts from a donor Selectric but now the return hub is ruined on the machine.


The threads and screws of the return drum I had pulled from this machine looked good, in spite of the drum not turning on the axle. I used clock oil and finessed the drum to come off the axle. I could see that the axle was really scraped up, the cause of the frozen position. Now I have a good drum that needs to go on the working axle I put into the machine.


What this portends is another major surgery. I will remove the cords, remove the entire assembly, mainspring etc before taking the bad return drum off it and installing the better drum. Once I am convinced that the return drum will rotate freely and then lock down when the screws are tightened, without stripping them out, I will put it all back together. Then back to the cord installation and adjustment. 


The front panel of the console printer (1053) has 16 toggle switches that comprise the Console Entry Switches, an I/O device the program can interrogate. My new console loader fits on the rear of that panel, underneath and inside the typewriter in unused space, with the wires running up to the console entry switches to virtually switch them while loading.

The remaining connections, to power and to the pushbuttons Prog Start and Load IAR, run out of a notch at the base of the front panel where the CES connections are routed down to the logic inside the 1130. One final connection, a USB cable, will run out of that notch along with my and IBM's cables. 

Here you can see me in the process of joining the console loader CES cable to the wires (white) I already installed on the toggle switches. Once this is done, I will wire in the other cable to the buttons then fashion the mechanical connections of the console loader to the back of the front panel.

Sunday, November 19, 2023

Typewriter 'whack a mole' getting the carrier return/tab/escapement cords set up


The cords were removed and I had to replace the drum/mainspring system with parts from the donor typewriter, documented in an earlier blog post. This left me with the tab drum sitting on the front of the shaft but not fastened down and the mainspring installed but not wound up. I hadn't put the two screws into the CR drum to fasten it on the shaft either, and neither cord was attached. 


The front of the shaft where the tab drum sits has a flattened area and the tab drum has a setscrew that will lock the drum on the shaft at that flat spot. I moved the drum so the gear on the drum edge would engage with the mating gears on the operational shaft, tight enough to meet the backlash adjust of no more than .006". The setscrew was tightened to lock the drum in this position. 


The mainspring was installed on the rear of the shaft and I could replace the mounting bracket for the motor start capacitor which otherwise blocks access to the spring. The procedure for reattaching cords first puts about five turns on the mainspring which would be the force remaining when the carrier is fully rightward. This is a minimum sufficient to power the spacing and tab movements of the carrier even at the right margin. 

Then when the CR drum pulls the carrier to the left margin it will wind additional turns on the mainspring. In normal operation, for a return operation the motor turns the shaft through the tab drum to wind cord on the CR drum, let cord off the tab drum, and wind power into the mainspring. All this energy in the mainspring is available to pull the carrier rightward whenever the escapement teeth disengage, either to space one column over or to fly to the next tab stop or all the way to the right margin. The power for rightward movement of the carrier comes from energy stored up in the mainspring. 


My next move was to attach the return cord to the CR drum, route it around its three pulleys and attach the other end to the bottom of the carrier which was sitting at the right end of the machine. When that was done I would manually turn the operational shaft to draw cord onto the CR drum, wind the mainspring and pull the carrier to the left side of the machine. 

When it reached the left side, I would then attach the tab cord to the tab drum, getting at least one wind on it while at the left side of the machine, route the cord over two pulleys and attach it to the right side of the carrier. Turning the CR drum on its shaft (since the screws were loosened to let it turn freely on the shaft), while turning the tab drum in the other direction, I could get the lengths of cord approximately correct and lock down the CR drum screws. 

Pulling the tab cord over the spring loaded pulley on the right side of the machine will indicate whether the tension on the cords is correct or not, by the position of the pulley against a fixed mark. Slightly loosening the CR drum screws and turning that while holding the tab drum/mainspring from turning, while differentially loosen or tighten the cords after which I can lock down the CR drum. 

Unfortunately, this is where the Selectric began to play whack-a-mole with me. That is the game where as you try to knock down a mole popping out of one hole, others pop up from different holes, such that you never have all the moles down at the same time. The theory sounds simple, per the manual.

Lets summarize the number of items that need to be controlled or manipulated for this all to work out:

  • CR cord attached to bottom of carrier
  • CR cord positioned around two pulleys on left side of machine, in the groove on each pulley
  • CR cord positioned over small pulley in rear of machine on post, in groove
  • small pulley does not jump or fall off post
  • CR cord wrapped smoothly around CR drum

  • CR drum turned and held to tighten or loosen CR cord
  • Tab cord attached to right side of carrier
  • Tab cord fit round the spring loaded pulley on the right side of the machine
  • tab cord fitted over small pulley on post above tab drum
  • small pulley does not jump or fall off post
  • tab cord wrapped smoothly around tab drum
  • Tab drum and mainspring turned to tighten the tab cord
  • CR drum turned on shaft to tighten CR cord without releasing tab cord
  • Two screws set 90 degrees apart on CR drum must be tightened down while cords in tension
I no sooner get the CR cord properly wound on the drum when the cord pops off 1 to 3 of its pulleys. I get the cord back on the pulleys and the end falls off the bottom of the carrier. 

The issue is the number of hands which need to be involved to keep all of the elements in their proper positions - one hand for the CR drum and one for the tab drum. Other hands so the cord tension doesn't slacken so much that it detaches from the carrier or loses the even wind on the drums. Other hands to tighten the screws on the CR drum. Eyes and hands to ensure that the two small pulleys don't jump off. Eyes and hands to make sure the cords run in the grooves on two small pulleys and three big ones, plus in two drums. 

I put in a good two hours until the last time that the CR cord fell off the bottom of the carrier. When next I get into the shop, with a packed Thanksgiving week in the way, I will ever so patiently reinstall it, thread the cord on all the grooves, fix up the drum wind and then try to get the tab cord started on the tab drum. 

Saturday, November 18, 2023

Selection latch restoration and rotate selection adjustment work


There are a number of adjustments to work through for the rotation selection and I am going to focus on getting them exactly correct, by the book, in order to achieve proper selection. Some of them will require me to power up the motor because the adjustment procedure requires the print cycle to occur at full speed. 

One of the earliest adjustments is to set up the rotary pivot arm so that it as close to vertical as you can get it. The various manuals suggest measuring from the line etched in the arm at the top and bottom in order to ascertain whether it is equidistant. The snag is that there is no 'thing' to measure to from which it would be equidistant. 

Vertical etched line with no surface to match

You can see the pivot arm with its line etched running up and down. Notice that there is no vertical surface anywhere in sight that you could measure from . The mechanisms behind the rotational pivot arm include the tilt pivot arm and they block visibility of the metal frame behind them, at any position where you can observe the pivot arm vertical line. The opening to the right of the pivot arm is quite deep and even at its far end there is no flat surface where a measurement point can be taken. 

Note the nonexistent reference structure to which the measurement is taken

The vertical positioning of that pivot arm is accomplished by moving a turnbuckle on the black rod you can see running from the bottom of the pivot arm rightward into the depths of the machine. This is what pulls or pushes on the arm to effectuate tightening or loosening of the rotate tape, which in turn causes the type ball to spin on its axis to one of the five positive or five negative positions away from its idle 'home' spot. 

When the vertical position is set by lengthening or shortening the black rod using the turnbuckle, a later adjustment has the black rod attachment moved up or down on the pivot arm to increase or decrease the displacement of the arm for a given movement of the rod. These two are interrelated and one must iterate to get them both adjusted properly. The later adjustment, the pivot point change, is intended to make the positive 5 and negative 5 rotations of the type ball turn the same number of degrees. 

Before I can set the pivot point, however, I have to set the 'homing' position of the type element. This is the resting or idle position, called home. The adjustment manual requires me to half-cycle the machine using a set of selection latch activations, under machine power. A special tool, which I own, sits on the cycle clutch and forces it to step halfway through the print cycle, when the type element has achieved its full tilt and rotation. This is the dynamic half cycle tool. 

Dynamic half cycle tool
Initial home position setting

I have to begin with a tilt 3, rotate 0 character from the 'upper case' side of the type element, which lets me adjust the ball. There is a setscrew under the bottom of the shaft holding the ball, which is loosened and then the ball rotated to make sure that the detent bar enters the teeth of the ball at the right point on the side of the teeth. 

Next we adjust the selection mechanism until the I/O Home and Latched Home position of the ball is identical. There is a balance arm involved in this adjustment, which tweaks the mechanism so the ball remains at the home or rest position, in exactly the same spot, when either of the home types is activated. 

Latched Home is a configuration where all the positive rotate latches R1, R2 and R2A are selected, e.g. they are NOT pulled down by the selection bail but R5, which controls the -5 rotation, is pulled down. With no pull on the positive latches there is no positive turn and pulling on R5 blocks the -5 action - a net zero rotation is produced. 

I/O Home is a configuration where the three positive latches R1, R2 and R2A are not selected, so that they are pulled down by the bail and would cause a +5 rotation of the ball. However, because the R5 is selected and does not pull down, it imparts a -5 action resulting in no net rotation. The balance arm adjustment is what ensures that the -5 action of R5 is as equal as possible to the +5 action produced by R1, R2 and R2A. 

The type element (golf ball) has teeth under each of its 22 columns (11 per 'case') with four characters vertically arranged in the column based on tilt position to achieve the full 88 character capacity of the element. A detent arm slides into the tooth to slightly turn the ball and anchor it in the precise rotary position for the desired column of characters. A similar detent arm locks the tilt mechanism to the precise degree of tilt to select which of the four characters in the column to print.

The selection mechanism pulls on the pivot arms and thereby tightens or loosens the two metal tapes for tilt and rotate. Each tape is hooked onto the carrier at one end and to a lever or rotating part inside the carrier with the tape's other end. Thus tightening the tape will pull the lever or cam in one direction, while loosening the tape lets springs move the lever/cam in the opposite direction as tension is relieved. 

During the print cycle, the selection ball pulling down on latches causes the selection mechanism to tilt two pivot arms, one for tilt and one for rotate, a given amount to move the lever or cam to its approximate correct position for the chosen character. The detent arms then move in and jog the type element to its final correct position. 

To work properly, the selection mechanisms have to get the tilt and the rotate position close enough that the detent arms always enter the proper tooth position to lock the ball correctly. The homing adjustments and all the checks as I adjust the selection mechanism are intended to ensure that we will have a good initial position as the detent arms begin to move in. 

The tilt mechanism does work correctly. The detent arm barely causes any adjustment to the tilt as the initial position is good. The rotate mechanism, however, is where we have problems. The machine presented with a failure to move the type element enough to reach the +5 or -5 columns before the detent arm moved in, thus we locked the ball to the +4 or -4 column incorrectly. 

All my adjustments are intended to get the typewriter to initially move the ball so that for any of the eleven rotate positions, -5 to home to +5, we are set so that the detent arm enters the teeth at the right point to ensure that we reliably lock the ball on the chosen column. 


The hanging selection latches are pulled forward by springs so that they will hook under the bottom edge of the selection bail. That bail moves downward during a print cycle, thus pulling down any selection latch that is under the bail edge. Choosing a character involves selectively activating some of the solenoids for R1, R2, R2A, R5, T1, T2 and AUX and any activated solenoid holds the selection latch out of the way so that it is NOT underneath the bail. Thus, an activated latch is not pulled down while an unselected latch moves downward during the print cycle. 

The selection latches are supposed to have just enough clearance when the print cycle ends, based on the stopping position of the selection bail, that they will restore or pop under the edge of the bail if they had previously been activated during the print cycle. This restoration is important, otherwise a selection latch might incorrectly remain off the bail edge and pull down when the solenoid did not fire to choose it. 

In order to adjust this, the manual suggests bending the metal stop tabs of any errant selector latch until it has a given clearance beneath the selector bail bottom edge when we are idle, not in a print cycle. It is very unusual to need to adjust one of these and nobody who worked as a typewriter technician (and who is reading the Golfball Typewriter Facebook group in order to respond) has ever seen a machine where all the stop tabs are wrong. I too worry that having them all out indicates some other error in the machine, thus bending tabs will put the machine further out of adjustment in reality. 

The stop tabs are just bent sections of the backing plate where the mechanism is mounted, bent forward at nominally 90 degrees but then bent to push the selection latch down so that it pops under the selection bail bottom edge when the print cycle is at idle. 

The selector bail pivots on a rear rod, pushed down by cams on the main operational shaft when they rotate during a print cycle. Rollers on the end of the pivot arm ride on the cams. The adjustments given for changing this part of the machine carry warnings that it should normally not need to be adjusted, but I can't see any adjustments of the position of the rod about which the selector bail pivots that might raise it at the idle point of a print cycle to let the selector latches restore. 

The design of the cams that move the selector bail up and down does move the bail a bit higher than its rest position at the start of a print cycle, then proceeds to move it downward to pull on any selector latches still under the bottom edge. Thus, in this typewriter where selector latches do not restore at the end of a print cycle, they will restore at the very beginning of the next print cycle when I am hand cycling the machine. 

The adjustment instructions insist on having the restore occur when the print cycle is at idle, however. The bail is held up by the rollers riding on the cam, thus there is no room for the bail to move further up; I can't hope for momentum during powered printing cycles to get the latches to restore. 


Friday, November 17, 2023

Rotate work continues on 1053; new version of console loader modification tested


I made adjustments of the rotate pivot arm and the long bar that transfers the rotate selection mechanism to the pivot arm, giving me a good +5 rotate selection but then the -5 isn't turning far enough. All of the selection latches for the tilt and rotate selection mechanism should be popping over the bottom edge of the bail that drives the tilt and rotate movement when the print cycle finishes, but on my machine all of them just fail to restore over the bail. 

The manuals state that the stop tabs should be bent to hold those latches a bit lower so they will restore over the bail. However, I find it hard to believe that all six of the stop tabs somehow are misadjusted. According to the typewriter pros that I chat with on a Facebook group, it is incredibly rare to have to bend even one tab and nobody has seen all of them need bending. 

The bail is raised and lowered by rollers that ride on a cam turned by the main shaft when the print cycle clutch is engaged. I compared their positions to that of my properly working 1053 from my own IBM 1130 and they appear to be identical. There is no adjustment other than the rotary position of the cams that determines how far down the selection bail moves.

When a print cycle starts, the bail goes slightly lower at the start which does allow all the selection latches to restore under the bail, but at full speed there is the risk that they won't pop under. That would cause erratic mis-selection of print characters. 


I supposed we could have had extreme wear that cut down on the diameter of the rollers on the cam or lessened the size of the cam, but I do not see any evidence of that. The cam is narrower than the rollers, thus the rollers would form grooves if they were eroded down. The cam has a nice smooth shape just like my working 1053, so I doubt that answer as well. 

I need to figure out what is different between the two, before I continue on this task. I don't want to bend all six stop tabs, which are metal L shaped protrusions from the bracket holding the selection mechanisms. These could snap if over stressed and if I bend them when they aren't the actual problem, it may further throw off operation of the machine. 


Further, I don't see how the latch restore problem is related to the failure to get the type ball to swing the full amount for +5 and -5 rotation positions. It may well be an evil coincidence that this typewriter has both of these issues. 


I originally designed a console loader as a request for a friend at a museum in the UK who wanted a quick way to enter large amounts of data into core memory while their card reader was inoperative. It was to be a quick and dirty fix for them, one that I built using an Arduino and some relay boards. 

The console entry switches (CES) on the front panel of the 1053 are a set of 16 toggle switches allowing the operator to set bit values in a word. The CES are used to load core, set the instruction address for execution and can be read by programs during normal execution. The logic gates that read the CES value are pulled down to ground through a 470 ohm resistor when a CES is turned to its on position. 

My solution used 16 relays and 16 resistors to activate the CES, assuming the operator has them set all to the off position when using my device. In addition. another relay board is used to activate push buttons that normally are pressed by the operator. When the rotary mode switch of the 1130 is set to LOAD mode, pushing the Prog Start button will cause the contents of the CES to be stored in core memory at the current address from the IAR, then the IAR is bumped by one to the next location automatically. 

To load a new value  in the IAR, either to store data in core with the LOAD function or to begin execution when in normal RUN mode, the operator sets the CES and pushes the Load IAR button. This is a normally open switch and my relay simply closes the circuit as if the button were pushed. 

The Prog Start button is more complicated it drives two complementary signal wires. +12V is routed to the normally closed contact when the button is not pressed, but instead that connection is opened and the 12V is connected to the normally open contact to energize that signal wire. I therefore need a relay that switches the 12V the same way, either to the NC or the NO contact wire. However, since the physical button is still active on the NC contact, I have to use an additional really to block the +12V from going to the armature of the pushbutton when my device is controlling the machine. 

That first implementation means that there are several relay boards that have to fit below the tabletop of the IBM 1130, squeezed between the 1053 typewriter front panel and the rear of the keyboard. A board of resistors sits on the side as well, plus the Arduino Mega must be located somewhere under there. It is crowded and messy as a result. 

The sixteen wires from the 1053 front panel snake out from under the 1053 panel. Note that the front panel can be separated from the 1053 typewriter itself, and the front panel can be lifted out of position. Thus there need to be connectors to disconnect my wires to the front panel. Another thing to squeeze in that limited tabletop space.

I verified this on my own IBM 1130, even though I have a different and easier mechanism on that machine allowing me to load and dump core memory locations. I installed another on the 1130 I am restoring. However, the messy nature of the implementation bothered me.


To solve the messy nature and build a more elegant version I decided to replace the relays with photo-isolator switches. These electronic switches are considerably smaller and allow me the opportunity to place the device in a better location on the IBM 1130. 

I designed and fabbed a printed circuit board that sits atop the Arduino Mega 2560 (a shield to use Arduino terminology), mounting surface mount versions of the photoisolators and resistors. The sandwich of the Arduino and its shield is small enough to fit behind the 1053 front panel. The typewriter mechanism has lots of open space in the front, below the row of three buttons for Tab, Space and Return. The device can mount on the panel and fit in that open space. 

It has a connector for the 16 wires from the CES and another connector for wires going to the area under the tabletop. These bring +12V and ground to my device as well as wires to hook to the Prog Start and Load IAR buttons. Thus, the formerly cluttered area now has a small bundle of six wires that run under the front panel of the 1053, with everything else out of sight.

I put together a test rig to verify the operation of the loader, feeding it +12V from a supply and using LEDs on a breadboard to indicate when the wires were energized. Everything worked as expected, so the device is now ready to be installed into the 1130 for its final test, removing the ugly version 1 of the console loader.

Testbed for loader device on left

I had also improved the program running in the Arduino in quite a few ways. The goal is to take a text file on a PC or other terminal, feed text lines to the Arduino over the USB serial interface whenever the Arduino issues a prompt character, and have that file control the operation of the loader device. It will always be active, listening on the USB connector for command lines. The format of the files was chosen to match the format that the Simh based IBM 1130 Simulator will dump memory contents. Thus the simulator can be used to prepare and test information, then those files used with my device to load core on the physical IBM 1130. 

The file has four hex characters per line to be loaded into the CES. 

  • A prefix character (default @) indicates that the Load IAR button is to be virtually pushed to put the CES as the next address. 
  • A different prefix (default =) saves the value as the location for the IAR to be used when the machine begins to run at the end of the session. 
  • A third prefix (default Z) tells the loader to put 0000 in the CES and push Prog Start as many times as the value of the four hex digits indicates, thus zeroing out a block of memory. 
  • If there is no prefix, the value put in the CES by the four hex digits will be loaded to memory by virtually pushing Prog Start. 
The device is inactive in its normal state. When a command line with only the activation character is sent (default #) then the Prog Start button is disabled and my device will begin responding to the other lines of the file. If not activated, my code ignores any command lines. At the end of the session loading memory, another command line with only the activation character is sent. This returns the Prog Start button to its normal operation and loads the IAR with the saved value if we had a = prefix during the session.

The code allows for reconfiguration of the characters to be used for the various prefixes and activation characters as well as other customization options. It has documentation throughout the code showing what is intended. 

To use the loader, a text file is generated manually or one is produced by the IBM 1130 Simulator. Simulator generated files need to have a first and last line of the activation character added as my device needs those to activate and deactivate. The operator turns the rotary mode switch to LOAD, turns off all the CES and then transfers the file over USB serial with the program on the PC/terminal sending one line every time it receives a prompt character. When the file transfer is complete, the operator turns the rotary mode switch to RUN and then pushes Prog Start to begin executing what they loaded into core. 

Monday, November 13, 2023

Adjusting rotate mechanism to properly select characters on typeball; performing a transplant


When I set the solenoids to choose a position on the typeball to print, the various latches cause the tilt and the rotate arms to pivot, pulling on the metal tape that allows the fixed position movements of the arms to be transmitted to the carrier mechanism which can be anywhere from left to right on the typewriter. 

The tilt selections work fine - the arm pivots to one of three positions or remains in its idle spot, which causes the typeball to pivot to one of four tilt levels. This selects 11 of the 44 characters on each hemisphere (upper or lower case) of the ball. 

The rotate selection does not move sufficiently to turn the ball all the way to its +5 or -5 position, instead mis-selecting a character on the +/-4 for printing. That arm moves between eleven positions - five positive and five negative, with the idle position selecting the eleventh possible character at this tilt ring. Rotate by itself chooses which 4 of the 44 characters are to be printed, with the tilt further refining that down to a single choice. 

The rotate spring under the golf ball maintains some tension on the rotate tape so that when the pivot arm moves inward it lets out some tape and turns the ball in one direction away from idle. When the pivot arm moves outward it pulls in more tape, turning the ball in the opposite direction from idle. 

A pivoting shift pulley on the other side of the typewriter can rotate in or out by a fairly large distance, pulling or releasing the rotate tape which turns the golfball between the upper case and the lower case side of the ball. There is an arrow on the golfball cap which points at the idle position of one of the hemispheres. The ball sits at idle with the arrow either facing the paper or 180 degrees away when shifted. 

The idle position is correct for the golfball, in that when the rotate pivot arm is in its vertical idle position, the ball has the proper characters facing the paper. I have the correct rotate spring tension and the idle (home) positions are correct in both upper can lower case. The issue I face is that the rotate pivot arm is moving less than the required amount when it moves out or in away from the idle position. 

I have also noted that the latches for tilt and rotate are not restoring themselves just under the actuating bar which moves them, which suggests incorrect adjustment of some stop tabs. This may be contributing to the incorrect rotation of the type ball. 


There is a rod that pulls or pushes on the bottom of the pivot arm, which causes the pulley at the top to move in the opposite direction. The point of attachment of this rod is adjustable, so I will move it closer to the arm's pivot point to increase the movement of the pulley for a given movement of the rod. 


The latches which are selected to cause the movement of the tilt and rotate pivot arms are supposed to just pop back under the actuation bar when the print cycle is done. A spring holds the latch under the actuation bar so that when the print cycle takes place and the bar moves downward, it pulls the latches downward. The solenoids for selecting a character will hold the latch away from the actuation bar thus when we select a solenoid for a latch, the latch will NOT be pulled down by the actuation bar. 

The downward movement of any latches which remain under the actuation bar cause arms in the Whiffletree mechanism to rotate. The length from the latch to the pivot of each arm is designed so that they deliver different amounts of movement based on the purpose of the latch. The latch which moves the ball one rotate position from home, R1, produces the least movement of the rod. The other latches produce increased movement and causes some to add or subtract to the movement when used in concert. 

Thus, the R1, R2, R2A and R5 latches can move the rod to any of the eleven positions in and out that should cause the golfball to rotate to its eleven positions. The amount of movement of the latch depends in part on where it starts from when the actuating bar moves it downward. There are stop tabs that sit above each latch and block it from moving upward past the tab. These are to be adjusted by bending them upwards or downwards until each latch will just pop back under the actuating bar at the end of a print cycle.


I saw that the entire block which has the stop tabs is attached to the frame with four bolts. I removed the motor from the rear to access the bolts, but there was not enough movement to completely resolve the stop tab issue so I will have to figure out how to bend them later. The access route for pliers to the stop tabs has the print shaft directly in the way. It might take some ingenuity. 

After moving the rod closer to the pivot of the rotate pivot arm, I was able to get to the full -5 position but the +5 still doesn't make it past +4. I think I can fine tune this to select properly. 


To get the cord tension correct for the cords that pull the carrier left and right during space, backspace, tab and carrier return operations, I need to rotate the CR drum and tighten the screws at the point where the tension is just right. The drum on this machine is extremely difficult to rotate. I believe it is corrosion between the shaft and the drum that causes the problem, since clock oil did nothing to free it up. The one time I did rotate it and tightened the screws, it slipped back to the original position anyway.

The donor Selectric I bought has a CR drum that rotates easily, free of corrosion. Swapping it does involve some major transplant activity, as the entire shaft that connects the CR drum, the tab drum and the mainspring has to be replaced. The shaft with the CR drum mounts on a back plate through a ball bearing. The tailpiece that locks to the mainspring is a nylon piece that is press fit on the back of the shaft. The shaft does slide through a front plate ball bearing and then into the tab drum. 

In addition to the drums mainspring and shaft, there are levers attached to the back plate that activate functions like backspace. The levers on the donor machine are different from the levers on the 1053. Fortunately, I saw circlips that allow the levers to be removed and attached.

The transplant operation began. The setscrew on the tab drum is loosened so that the shaft can pull out of the drum. I unscrewed the back plate and then began to free up the various levers and other parts. One dangling lever is the activation mechanism to drive the backspace power from the operational shaft clutch, which has a spring to pull it back out of the way unless it is being selected by the clutch. 

I carefully detached the spring, pulled the lever out of the operating mechanism and maneuvered the various levers behind the machine to free up the plate. I had to remove part of a microswitch and take off the motor start capacitor mount as well. The two cords were completely removed from the drums at this point. 

The 'patient', mid transplant

Once the old plate with its CR drum was removed, I began the swap of the levers between the original and the donor plates. I have many of the special tools that IBM repair people used to work on Selectrics, including a circlip insertion tool that came in very handy here. I verified the easy rotation of the CR drum on the assembly I will be putting into the typewriter. 

Two plates with drums, ready to exchange levers

I did work on the original CR drum and shaft a bit. Even with two vicegrips, it was difficult to rotate the drum on the shaft and it felt very gritty and uneven. The donor machine has paid for itself several times over by this point.

Reinserting the assembly is a complex reversal of the removal steps. There are levers and other parts inside the machine that need to be moved to a specific orientation before the plate with the drum can be slid back into place. The tab drum on the front needs to have the setscrew positioned over the flattened section of the shaft front, while all the levers and parts are in the proper orientation, including the dangling lever, before it can be screwed into place. The small spring was replaced on the dangling activation lever, the start capacitor mount reinstalled and finally I am ready to begin the next steps.

Tomorrow I will reattach the tab and CR cords, get them wound properly, attach the mainspring, wind it to proper tension, then rotate the new CR drum to set the correct cord tension. I am hoping this is a relatively straightforward and quick task now that the bad drum is replaced. 

Thursday, November 9, 2023

Working on tab/CR cord tension adjustment


The bolts that fasten the CR drum in position on the axle are how you adjust the cord tension. Loosening the two bolts, which are spaced ninety degrees apart around the hub, should allow for the rotation of the drum to pull on the cord until it reaches the proper tension. Then the bolts are tightened to lock the hub onto the axle.

The last times I did this, after struggling to get the drum to rotate on the axle, the bolts didn't hold the position so that the cord worked its way to be too loose. I removed the bolts, cleaned their threads and put a bit of lacquer thinner to loosen any sludge in the threaded holes on the hub. That might give them a bit more tension on the axle, but it is not certain that this will work.


I do have the donor Selectric typewriter that I bought, which has a very nice assembly with a CR drum that rotates freely. I am considering swapping this for the current assembly on the 1053 to be able to more easily turn and tighten the drum to hold cord tension. 

The assembly is a large bracket with the axle rotating in a bearing set in the middle portion of the bracket. The end of the axle has a nylon cam that connects the mainspring to the axle to power the forward (tab and space) movement of the carrier. The axle has its flattened section on the far end, where the tab drum will slide on and be locked into place with a single setscrew onto the flat surface. 

The major hassle in making this swap is that I will need to readjust the positioning of the tab drum for the proper position, engagement and backlash into the gears on the operational shaft. I am reviewing the procedures and assessing my access to the area to accomplish these adjustments without incurring more dramatic disassembly of the typewriter. 

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.