New gears arrived for the 2501 card reader restoration

NEW HOPPER GEAR CAME OUT CORRECT FROM SAME STL FILE AS THE OTHER

The first gear I had printed using the craftcloud3d.com broker service did not have the correct high walls. This new print had the exact same STL file sent but it was done properly. The printing service that did a good job was Detroit 3D Manufacturing, someone I will select when I use the broker service again. 

By comparison, look at the old order made by 'elipac 3D' where the wall and the outside teeth end prematurely. 

NEW STACKER GEAR TO REPLACE THE ONE THAT SNAPPED

I had a hopper gear whose teeth bent inwards towards the center as the extended further up from the bracing at the bottom. To get this to fit on the aluminum disk which forms the gear I had to attempt to bend it slightly but it broke in half. The gear did match the STL file, but the result wasn't good. 

Friends suggested a change in material that would suffer less from the deformation and bending of the sides of the teeth, so when I reprinted I selected a different plastic. I also used 'Detroit 3D Manufacturing' and in this case also the part was excellent when I received it. 

Comparing it to the prior gear, the one I snapped, I believe this new one is to be superior on the merits of the printing quality. The picture below of the snapped older gear isn't very sharp, I am afraid.

RECOVERY FROM KNEE REPLACEMENT - BEATING EXPECTATIONS

On Monday 21 April I had my right knee replaced, was walking with the aid of a rolling walker that night. Before I was sent home on Tuesday morning I could already bend more than 105 degrees and almost fully straighten the knee. I never needed pain killers outside of Tylenol and had remarkably little pain. 

The Wednesday 23 April I was able to walk without the walker as a support. I could do marching steps backwards and forwards at the Physical Therapy facility on Thursday as well as stand on the repaired leg while tapping my good foot back and forth, all with good balance. 

The only consequences of the operation are the swelling of the leg and bruising, but as long as I continue all the exercises and ice it frequently, those will greatly reduce or disappear in a week. I am extremely optimistic about resuming my workshop activities - except for any that might require me to kneel on the new knee - within a week. 

Working on a way to run DMS-2 on an 1130 without a working card reader and line printer

CHALLENGE FOR SOME OWNERS OF IBM 1130 SYSTEMS

The IBM 1130 was developed by IBM in the era of batch processing. Input was punched onto cards, work was processed serially and the results were output on line printers. Many users might share a machine by submitting their decks of cards. The decks were stacked in the reader, processed one by one and the output pages were returned to the user later. 

There were some alternatives for input and output, but the bulk of processing involved card decks and printed output. A keyboard, console printer (typewriter), switches, paper tape reader/punch, plotters, disk drives and other devices offered those alternatives. 

The controlling software for the IBM 1130 was Disk Monitor System (DMS). The latest version of the software was release 2, with most people referring to it as DMS 2. Enhancements and fixes to bugs were rolled out in incremental versions. The last official release was DMS V2 R12 although some bug fixes could be applied if you wanted a 'V2 R13'. 

Most IBM 1130 systems came with one internal disk drive which used 2315 cartridges holding about 500K words. Additional drives could be attached (IBM 2310 or 2311) for larger installations. DMS 2 was installed on one or more cartridges. 

To start the system, a boot card was placed in a card reader and the Prog Load button on the console loaded that in memory and began execution. That card's program would fetch in DMS 2 from a disk drive and turn over control to the monitor. The first thing that DMS 2 would do as it started was to print a page on the line printer, pretending that it had read a control card (// JOB) from a card reader. 

Decks started with a // JOB card to delineate a new element of work, often a new user. The deck is read by DMS 2 to find control cards - these can start compilers like Fortran or utility programs like DUP (Disk Utility Program) or user programs (// XEQ). The programs such as a compiler will read cards to accomplish its part of the job, then return to the monitor to look for the next control card. One might call a compiler (// RPG) then run the program (// XEQ). When the monitor finds the next // JOB card, it begins the next job. 

In general practice, to load DMS 2 from the disk requires a boot card (cold start card) in a working card reader. DMS 2 won't fully start without a working line printer to display that first // JOB card. It tries to read cards from the reader in order to find control cards. If an installation does not have a working line printer and a working card reader, nothing can be accomplished. DMS 2 waits at a special location x002A with a code in the accumulator register (ACC) showing which device is not ready or not working properly. 

While you could toggle in some code to memory to act as the cold start card, once DMS 2 is loaded from the disk drive, it will wait for the missing line printer. If that barrier were overcome, it would then wait for the missing card reader. This makes demonstrating an IBM 1130 in a museum challenging unless you have the printer, card reader, and disk drive working. 

DMS 2 DID NOT PROVIDE DEVICE INDEPENDENCE

Device independence is a common design objective with operating systems to provide a common interface that allows a program, without modification, to use different device types. Within reason - you can't expect to read data from a plotter for example - but modern software might allow you to read from a card reader, a tape drive, a disk drive, a keyboard, as well as multiple types of card readers. 

This was not a general capability of DMS 2, with only a primitive degree of independence provided. Printed output could be directed to the 1132 or 1403 line printers, or to the console printer (Selectric based typewriter). However, the program had to format the output in the character code of the specific printer being used, so that it had to be modified if you switched between printer types. 

For input of decks, the 1130 could use the 1442 or 2501 card readers, the keyboard on the 1130, or the 1134 paper tape reader. The character code of the paper tape reader differed from the Hollerith code used with the first three devices. 

DMS 2 was generated for an installation, tailored to the devices being attached to the machine. As part of that tailoring, DMS 2 assigned one card reader and one line printer as the principle input device and the principle output device. This is the primitive level of device independence offered. 

When reading control cards, DMS 2 would refer to the principle input device rather than the specific 1442 or 2501 driver. Similarly, when printing the // JOB card and other monitor data it would use the principle output device instead of the specific 1403 or 1132 device drivers. 

Installations could have multiple types of readers and/or line printers. DMS 2 would always use the one assigned as the principle device, but user programs could read/write to the device of their choice which made use of the specific device driver. 

CONSOLE PRINTER AND KEYBOARD AS ALTERNATE PRINCIPLE DEVICES

DMS 2 did allow the console printer and the keyboard to be used as the principle devices by reading specific control cards. The // CPRNT control card would switch the principle output device from a line printer to the typewriter. The // JOB card and other monitor output is typed on the console printer. This continues until a // CEND card is read which changes the principle output back to the assigned line printer. 

The change of the principle output device was written back to disk, so that any time you booted DMS 2 after a // CPRNT had been executed, the monitor output would be typed rather than sent to a line printer. This could resolve the problem where DMS 2 hangs at startup due to a missing line printer. 

DMS 2 could switch the primary input device to the keyboard when it executes a // TYP control card. All subsequent monitor cards are read from the principle input device, e.g. from the keyboard. This is NOT written back to disk however so upon a reboot DMS 2 would again hang waiting for a missing card reader. 

Using the console printer and keyboard is very cumbersome and impractical for meaningful decks to be entered. DMS 2 and its programs used fixed columns for card fields, unlike the free form input of most modern systems. An Assembler input card      LOOPX LDD I *-4 must match the column requirements of the assembler. 

• Columns 1 to 20 are ignored  
• Columns 21 to 25 are the name field of the statement, with any name left justified in the field
• Column 26 (and 31 and 34) are ignored
• Columns 27 to 30 are used to enter an operation code or assembler directive name, left justified
• Column 32 is used to mark a long format (doubleword) instruction using L or indirect using I
• Column 33 is used to select one of three index registers entering 1, 2 or 3
• Columns 35 to 71 hold the operand, left justified
• Columns 72 to 80 hold card sequence numbers, used to sort a card deck into order

If using the keyboard, the user would need to space precisely to column 21, 27, 32, 33, and 35 in order to type in the left justified nonblank input. There is no way to go back to earlier 'cards' to make changes, only some primitive line editing for the current 'card'. 

Perniciously, it takes a working card reader to read in a // TYP in order to switch to the keyboard. Since the change to keyboard is not recorded on disk, each boot of DMS 2 returns to the card reader as the principle input device.

STRATEGY TO CORRECT THIS

I think the most straightforward way is to cold start DMS 2, with it having previously processed the // CPRNT card making the typewriter our principle output device. It will type out the initial job card information and then stop at x002A with a card reader not ready condition.

I will work out how to enter a // TYP card in the buffer and a way to branch into the card reader to make it return to the monitor claiming a successful read of a card. The monitor will process the // TYP, changing the principle input, leading to the Keyboard Select lamp lighting on the console next.

I did a lot of source code examination of the monitor logic that reads the control cards as well as the device driver for the card reader. It isn't enough to zap the disk image after a // TYP because the execution of that command loaded a different device driver and changed quite a few words in core. That would mean I would have to update a substantial number of memory words to place the correct driver and control words in core. It is easier to let the monitor handle the work by feeding it a // TYP card.

METHOD TESTED ON IBM 1130 SIMULATOR

The card buffer for the monitor control records sits at 0x0faf with the first word containing the word count (0x0050 or 80 columns) for the read. The data in that buffer is read as Hollerith characters but the card reader routine will convert them to EBCDIC characters before they are processed as monitor records. 

This means the desired card - // TYP - reads in as 3000 3000 0000 2400 2020 4040 0000 0000 . . . 0000 but when it is converted and packed two characters per word, it becomes 6161 40E3 E8D7 4040 4040. . . 4040 instead. I have to load the buffer with the Hollerith values, then branch back as if the card read device driver finished the read and now wants to convert it. 

I was doing something wrong because the conversion is not completing successfully. I see the card columns converted from Hollerith to EBCDIC but they are not packed two characters per word. I thought I must be branching to the wrong place. 

After tracing the execution a bit, I realized that it there was some flag that wasn't right so it was trying to read another card. If the flag had been correct it would have branched to the routine to pack the characters two per word and then process the command. I set the IAR to that routine and started execution. It worked!

PROCEDURE ON A SPECIFIC DISK

On the disk I had loaded with DMS 2 and previously configured for printing on the typewriter, the monitor control record processing code sat starting at x04FE which determines the locations to use in the procedure. It is likely that other disks will use the same address if they were loaded with the same version of DMS 2 but I would always test to be certain.

Boot DMS 2 and verify it is at 0x002A with 0x3000 in the ACC register - wait for card reader not ready. 

The card buffer sits at 0x0fb0 to 0x0fff. The first step is to clear that buffer to all spaces - 0x0000 then enter the Hollerith code of our // TYP card. Starting at 0x0fb0 we enter:

• 3000
• 3000
• 0000
• 2400
• 2020
• 4040

The IAR is set to 320, the address where the card reader routine will execute to return after it has successfully read a card into the buffer. Press Prog Start and the machine waits again at 0x002A with 0x3000 in the ACC. Set the IAR to 5C6 and press Prog Start. The Keyboard Select lamp will light on the console indicating this has worked, plus the // TYP card will be typed out on the console printer. 

LIMITATIONS OF THIS WORKAROUND

This process will allow DMS 2 to be run and some work can be performed using the console printer and keyboard as the principle output and principle input devices. However, many programs will use the actual device driver for line printers rather than go through the principal output device. This will cause them to stall at x002A with a printer not ready condition. 

For example, I was able to invoke DUP with a // DUP card and that program did read its input from the keyboard. However, when I invoked the DUP command *dumplet to list the contents of the disk directory, the output went to the 1132 line printer and not the typewriter. 

IBM 1130 typewriter (console printer) repair and adjustment - part 6

ATTEMPTING TO FIT MYSTERY PART DISTURBED A PLATEN ADJUSTMENT

One point where they mystery typewriter part might have been attached was the inside post behind a screw with locking nut that adjusts the platen (roller upon which the paper rests). I had to partly remove the post in order to slip the part over it, but once it was clear this could not do anything useful, I pulled the part off. 

Unfortunately, tightening the screw left the platen misadjusted. This caused the carrier to partly jam as it tried to move along past the paper and platen. I had tried to run the Console/Keyboard diagnostic to check out my typewriter adjustments but ran into the jamming right away. I will need to set this adjustment properly before I proceed. 

MOVED COMPONENTS OVER TO THE NEW 2310 INTERFACE BOARD PCB

The new PCBs arrived from the fabrication service. I chose to desolder and swap the parts from the bodged older board, to have a fully correct version of the Virtual 2315 Cartridge Facility for use with the two IBM 1130 systems that will receive it. This was easy to complete and the new boards are ready for installation. 

IBM 1130 typewriter (console printer) repair and adjustment - part 5

ADJUSTING TAB OPERATION

I had two issues to address. First, the metal part that supports a plate under the platen (roller) was too close to the tab torque bar plate and could interfere. Second, the tab stop plate on top of the carrier was not adjusted correctly. 

For the interference issue, I studied the maximum rotation of the tab torque bar and determined that it would not be reaching the point of interference as it reached and went slightly beyond its high point. There is a stop tab that is set to block it from moving too far up and that was properly adjusted.

That left only the important function of opening a microswitch during the entire time the carrier is moving to the right in a tab operation. To accomplish this, the tab torque bar must be prevented from restoring to its idle rotational position until the carrier reaches the next column where a tab stop is set. This typewriter was starting the tab movement but restoring immediately, before the carrier motion has completed. 

CHALLENGE FINDING MECHANISM THAT SHOULD HOLD TAB INTERLOCK

The Theory of Operations manual shows a raised lug on the back of the tab trigger lever, but that does not exist on my machines - either of them. That is what should hook under the lever and keep it twisted away from its idle position until the tab lever itself is reset upon reaching a tab stop column. 

The parts manual does not show the lug either. It doesn't show any part that would act to hold the lever from returning immediately as the operational cam finished the rotation to trigger the tab movement. That matches what is occurring on this machine where the switch closes again right after the tab movement is initiated and well before it ends the movement to its new column. 

A suspicion arose - could this be related to the mystery part that I can't locate in the parts manual or on the machine? Perhaps it provides a latching action to hold the microswitch assembly open once it is begun by the tab operational cam rotation? What I don't see right away is how it would be released when the carrier reaches the tab stop column, but I can try to install it and puzzle out the behavior.

Above is the drawing from the parts manual which does not show that part. Below is a very quick slapdash drawing where the part might fit on the machine. 

TESTING FIT OF MYSTERY PART INTO THE TAB MOVEMENT LOCK MECHANISM

There was no orientation or placement for the part that would do anything useful with the tab switch. The mystery part remains a mystery but is unrelated to the tab interlock issue. 

I SPOTTED THE LUG MENTIONED IN THE THEORY OF OPERATIONS MANUAL

The Theory of Operations manual mentioned a lug on the rear of the tab trigger lever that would hold the tab torque bar partially rotated, but I didn't see any signs of a lug or other projection. However, when I was bending the torque bar for another look, I noticed that the escapement bracket (rear of the carrier) had a hole in it into which a spring disappeared. I had believed this was only used to allow the spring to pull the tab trigger lever back to idle position, but I saw a glint of metal inside there.

REPAIR MADE, TAB SWITCH STAYS ON DURING ENTIRE TAB MOVEMENT

I realized that the lug was indeed on the lever but it was bent back so far that it stayed inside the 'tunnel' of the hole on the escapement bracket. I used a small screwdriver to bend it forward. The mechanism worked correctly! 

This is NOT an adjustment or check mentioned in any of the IBM maintenance manuals for the IO (Input Output) Selectric models. The line of IO Selectrics is broad, with models having keyboards and others like the IBM 1130 console printer that are output only. Some were developed for banking, some for remote terminal access to timesharing on the mainframe, and some were consoles for various computer systems. 

The manuals are filled with details that pertain to only certain models. Further, they mention iterations of the design, such as version 1, 2, 3 and 4 of the escapement mechanisms. It is difficult to build a parts manual and documentation for all those variations. Still, both of my issues were due to missing information so I can't give them an A rating.

The tab switch is only needed for the IO models in order to block any letters from printing while the carrier is in motion. An office Selectric would not have this problem because the human typist would not press keys fast enough to have them print while the carrier was still moving. 

POWER ON TEST OF TAB LOOKED PERFECT

I set up the typewriter with a long distance between stops, turned on the computer and watched the behavior doing tabs. The RETURN button got the carrier to the left column, then the TAB button caused it to zip to the right until it reached the column where a stop was set. The microswitch lever remained activated throughout the motion and reset as the carrier stopped. 

Hiatus as I recover from a total knee replacement

APRIL 21 IS THE SURGERY DATE FOR A REPLACEMENT OF MY RIGHT KNEE

Arthritis settled into my right knee, I believe accelerated due to the complete quadriceps tendon rupture I suffered back in 1998, where the repaired knee grew bone spurs in multiple locations. About three years ago I experienced a few events which I ascribed at the time as injuries to the knee but were in fact the degradation reaching a tipping point. 

It is time to have it replaced, having bought time with steroid and gel injections for the last six months waiting for the best surgeon in the area to slot me into his schedule. Monday April 21 is the day! I should be home by Tuesday, but it will take a bit of time to recover. An ice machine will cool the leg to reduce swelling and a variety of medications will support me as the injured tissues stop complaining. 

I will receive physical therapy starting on Wednesday April 23rd and anticipate that I should be relatively mobile in 4 to 6 weeks. In the first few weeks, however, it is unlikely that I could return to work on my various projects in the workshop. Thus, a pause is coming. 

NEED TO RECOVER ENOUGH MOBILITY TO SAFELY MOVE IN THE WORKSHOP

I not only have to be able to move around reasonably well with limited pain, but need to be sure that the workshop aisles and workbenches are safe for me when I may be depending on a walker or cane. This is one of the gating factors for when I can resume progress. 

IBM 1130 typewriter (console printer) repair and adjustment - part 4

READJUSTING THE REMOVED PARTS

Selection Stop Plate

This is a simple adjustment, just a bit awkward due to the narrow zone where the wrench has to fit to tighten the screws while holding the plate from moving.

Cycle Clutch

As you can see from the multiple diagrams above, the print cycle clutch has quite a few settings that must be checked or adjusted in order to work properly. I methodically moved through them. Most are easy to measure and straightforward to change.

C2 Switch

I hook up a VOM in continuity mode to the switch. The hand cycle tool I used to turn the shaft of the typewriter has degree markings, which gives me a way to measure where the switch contacts are opening and closing. 

The adjustment is done by rotating the cam and then moving the bracket around until the make and break points are achieved. First I had to disconnect the switch bracket in order to get to the two setscrews that hold the cam on the shaft.

I then loosened the two tiny setscrews (at 90 degrees from each other) and turned the cam to achieve the proper orientation while the cycle shaft was at rest. 

The bracket was replaced onto the frame and moved until the contacts just broke while the print cycle shaft was left at the 20 degrees of operation point. I then verified that the contacts reconnect right around 120 degrees of print cycle movement. 

Filter Shaft

On normal office typewriters, those with keys that are pressed by a human, the key latches down and has to be reset at the end of the print cycle to allow the next keystroke to be accepted. The filter shaft has a cross section that is a very thin oval, the two ends are what push the keys back to the restored position. 

This rotates as part of the print cycle, which is a 180 degree turn of each shaft, thus the two lobes on the filter shaft. In addition to its (unnecessary) role of restoring keys, this has a cam which pulls a rod to trigger a space of the carrier. A pawl is briefly pulled out of the rack of teeth that hold the carrier in place, so that the coil spring energy pulls the carrier to the right where the pawl falls into the next tooth (column). IBM calls this spacing action escapement. 

We want to move the carrier after the typeball has already begun moving back away from the paper and ribbon, not while it is still in contact, otherwise we will get a smear instead of a clean letter. The cam is adjusted so that it pulls the rod after the critical position of the ball is past, yet still releases the pull rod when the print cycle comes to rest. 

This was straightforward to check and was set correctly. The filter shaft on this keyboardless typewriter used a circular shaft rather than the oval version from office typewriters. 

Carrier Print Shaft

This is a very important adjustment. It rotates the rod that the carrier slides across, thus it turns the mechanisms inside the carrier. A notch runs along the length of the rod into which the various cams in the carrier are keyed. 

A print cycle begins when one or more solenoids are engaged by the 1130 to request a particular letter to be printed. These solenoids pull on levers that dangle under a wide plate, so that the lever is either under the plate or out of the way. The plate will be forced downward during a print cycle, thus pulling all levers that are still under the plate.

The print cycle clutch is triggered by the activation of any solenoid. It releases the print mechanism to turn 180 degrees before the clutch latches back to idle. As the shaft turns through the 180 degrees, it is rotating cams that push the selection plate downward. 

The downward pull of the levers that were selected cause the mechanisms in the typewriter to change the tension on two thin metal ribbons that are routed to the carrier. One of the ribbons turns the typeball left or right, achieving one of 11 rotation positions. The other ribbon tilts the typeball to one of four rows of characters. Thus the selection picks one of the 44 unique type characters on the ball. 

As the print cycle proceeds, the shaft running through the carrier is turning. It begins moving a set of latches which will first lock the ball to the tilt setting and a bit later push a lever up into a tooth on the typeball to lock in the rotation setting. 

During our print cycle, we have two sets of motions occurring. The metal ribbons are moving based on the selected levers and downward plate movement. The locks are engaging and releasing for tilt and rotate.

These must be synchronized. If the selection mechanism is still moving a ribbon, not yet at its final rotation or tilt tension, but we lock the ball then we have two bad things happening. We may have selected the wrong character, locking the ball before it gets to the intended target. We are also locking the ball but putting tension on the ribbons, which might cause them to break. 

This is why we want the shaft going through the carrier to be in a very precise relationship to the print cycle overall. We want to see the typeball move to its intended position just before the latches lock down the typeball. We also want to see the typeball unlatched before we begin restoring the ribbons to their rest position as the selection plate and levers move back up. 

I hand cycle and carefully observe the motion of the ball and of the latches, both at engagement of the latch and at release. The shaft position at idle is adjusted until I am satisfied with the synchronization. This is all checked with extremes of rotation and tilt, the worst case for problems in timing. Thus I selected characters with a +5 and a -5 column and a tilt of +3. All worked properly. 

Gear Lash

This is an easy adjustment, which must be done to allow smooth movement of the print clutch shaft, filter shaft and carrier shaft gears as they mesh and turn together. We don't want too much friction nor too sloppy an engagements. 

Final Checks

I first checked that the print shaft going through the carrier is in the right orientation, with the groove in the shaft just a bit rearward of straight up, about the 11PM position on a clock dial. I also checked the position of the cams for the spacing and shift mechanism lockout, as they need to be at the proper place when the cycle is idle. 

I then check for malselection of various characters, using the hand crank to see when the locking bar enters the teeth on the selectric type ball. I had to do this for both upper and lower case positions, testing -5 and +5 rotate operations. All appeared to be correct. 

Hand cycle tool to manually operate typewriter

TEST UNDER POWER

With the console entry switches (CES) removed from the front panel, the typewriter could be moved four to five feet from the 1130 due to the long cable. I plugged the SMS power and signal cards back in with the typewriter on a table next to the 1130, so that I could run it under power to see how everything works.

The front panel buttons Tab, Space and Return were pushed to observe how the carrier moved. Everything else will be tested by commands issued from the IBM 1130.  I let the residual code from the disk diagnostic run to print a few messages.

It was obvious that the mechanism to hold the tab microswitch open was not working properly. The tab torque bar snapped right back to idle position while the carrier was still in motion. This was reflected in the typed output which was distorted when new commands were issued during a tab move. 

I also noticed something different between this typewriter and the one on my personal 1130 system. The tab torque bar lever that activates the microswitch is able to jam against a metal part that is part of the paper movement system. 

Specifically, the platen (roller that the paper curves around) sits on four small roller shafts and has a metal plate that forms a sandwich of platen, paper and this plate. This extends for about a third of a circumference of the platen centered near the bottom. The metal plate sits on two metal parts, one at each end of the typewriter. 

You can see in the picture above that the metal part extends out to brush against the end of the torque bar plate as it rotates up. Compare that to the position of the metal part on my typewriter, shown below.

REPLACED TWO OUTPUT BUFFER CHIPS FOR V2315CF MAIN BOX

Due to an error on the 2310 Interface Board PCB, one of the control signals from the Virtual 2315 Cartridge Facility (V2315CF) was exposed to 12V when it was intended as an output to drive a MOSFET transistor. The signal would turn on the Unlock lamp on the 1130 console when the V2315CF did not have a virtual cartridge file loaded and it was operating in virtual mode. In its real mode, the 2310 disk drive inside the IBM 1130 would directly control that lamp.

I received a supply of replacement buffers for both input and output signals from the V2315CF and installed one on each of the two V2315CF boxes I had built. Having hacked the existing 2310 Interface Board PCB to cut traces to the 12V supply and add a bodge wire, it is now safe for use. The new version of the PCB should arrive tonight so that I can create an unhacked version for production use. 

IBM 1130 typewriter (console printer) repair and adjustment - part 3

UNSUCCESSFUL HUNT TO IDENTIFY MYSTERY PART FROM TYPEWRITER

During the disassembly required to replace the broken motor belt in the console printer/typewriter on the IBM 1130, one part that dropped out confounded me when it came time to reassemble the mechanisms. I didn't see where it came from and I can't see any spot where it makes sense to be attached. 

Yesterday I spent more than an hour scrutinizing the parts manual for the device, looking at every diagram no matter how unlikely it might seem that the part is associated with the diagram. Nothing that looked like the part was in the manual.

I then spent about an hour looking over my own IBM 1130's typewriter, hoping to find where the part was installed on my machine. As with the parts manual, I was unsuccessful. No sign of the part anywhere on the typewriter. The typewriter is composed of thousands of parts, with many deep dark nooks and crannies.

I had been adjusting my own typewriter when I moved to this new workshop, thus there were a few parts removed from it. I looked at the container holding those few parts and - voila - the mystery part was there. This confirms that it goes on the typewriter but gives me no clue as to where. Sigh. 

WORKING ON THE TAB FUNCTION INTERLOCK SWITCH

A tab operation on a typewriter causes the carrier to move a varying number of columns to the right, stopping when it reaches a column that has a stop tab set. I have written extensively about the mechanisms involved in prior posts, which I won't repeat here, but I will mention just a few essential points to provide context for the work I did yesterday.

To start a tab, the operational clutch is triggered by the tab button or the tab solenoid fired by a write from the 1130 to the typewriter. During the fixed timeframe while the operational clutch rotates 180 degrees, it twists a torque bar that runs from right to left across the machine just behind where the carrier travels.

The torque bar has a roughly rectangular cross section, with the longer side positioned vertically. When the bar twists, the wide side pushes a lever away from the carrier and latches it in the out position. This pulls a pawl out of a rack of teeth which keep the carrier from moving to the right. Energy in a coil spring pulls on a cord that is tied to the right side of the carrier, thus with no pawl in the teeth the carrier is accelerated to the right. 

A projection on the lever that is latched away from the carrier will strike a plate at any column where a tab stop was set (by moving the plate to the position where it will be struck). Hitting the projection forces the lever to unlatch, the pawl to fall into the rack of teeth, and the movement to stop. 

Since the movement across from left to right takes a variable amount of time, based on the number of columns traversed, and because this takes longer than the time that the operational clutch was rotating, a means is needed to signal the IBM 1130 that the typewriter is mechanically busy. If the 1130 were to issue a character print command, that would print randomly during the tab motion. 

To block commands being issued during busy times, the typewriter has a chain of four microswitches that can open their contacts to indicate that mechanical motion is underway. These cover printing a character, shifting between hemispheres of the typeball, carrier return and a tab movement. 

The end of the torque bar on the left of the typewriter has a plate that rotates upwards as the bar is twisted. This allows a spring loaded lever to move upwards, transferring through another part to open the microswitch for tab motion protection. 

The blue arrow points to the microswitch that is opened while the torque bar is twisted. The red arrow points at the torque bar and the green arrow is the lever that moves up when the torque bar is twisted. 

The green arrow points at the plate on the end of the torque bar (see blue arrow), as viewed from the top of the machine. The lever is underneath the plate and not visible in this picture. 

The torque bar should be held partially twisted as long as the lever is latched away from the carrier and the carrier is thus in motion. When the projection strikes the plate for a tab stop, the unlatching of the lever allows the torque bar to restore to its idle position. That pushes the parts down to close the microswitch again. 

The problem I discovered was that the microswitch was not remaining open for the duration of a tab motion. It would briefly open during the time the operational clutch was rotating but then it closed in spite of the fact that the carrier was still moving to the right. 

The lever for tab was not holding the torque bar partially twisted because it hadn't reached a critical angle of twist during the tab request. It turned far enough to latch the pawl out of the teeth, so the carrier moved, but not far enough to latch the torque bar in a twisted condition. A metal plate called a tab overthrow stop was what capped the maximum movement of the torque bar and lever. I adjusted this and the typewriter now holds the microswitch open until the lever is unlatched at the column where the tab movement stops. 

I believe the erratic printing I observed while running the disk function diagnostic 309 was mainly due to the incorrect operation of the busy signal for tab movement. Attempts to print and to perform carrier returns were issued while the carrier was still in motion from a tab movement request. We will see how it behaves when I run the console printer/keyboard diagnostic at the end of this repair and adjustment project. 

IBM 1130 typewriter (console printer) repair and adjustment - part 2

BELT REPLACEMENT

The belt between the motor and the operational shaft is blocked in by the print cycle clutch on one side and a metal bracket through which the operational shaft passes in a bearing. Thus I have to remove some part of the shafts to make room for the belt to be fitted around the shafts. 

The print side (left side when looking from the front) is easiest to take apart with minimum adjustments needed upon reassembly. I remove an assembly with intermediate gears that connect the main shaft with others such as the print shaft that the carrier slides along. With that removed, I can unhook the end of the main shaft to pull it partway out.

The motor belt turns a pulley that is one end of the operational shaft, the part that rotates continuously as long as the motor is turning. The pulley has the print cycle clutch attached to it. That couples the turning motion to the left shaft when a character is being printed other wise the shaft to the left of the pulley does not turn. 

When I pull the left shaft out of the pulley and print cycle clutch, it opens a gap that I can maneuver the new belt through. There is a little bit of wiggling and twisting involved, but it is easy enough to fit the belt around the pulley with the other end extended back to the rear of the typewriter where the motor sits. 

This plate holds the end of the shaft that extends to the print cycle clutch. I have several parts to remove in order to be able to pull the shaft leftward and open a gap. 

You can see two screws across the bottom that hold the cam operated microswitch (C2 switch) assembly to the typewriter. The black plate holding the end of the shaft has two screws plus a nut to remove. There are plates, nuts and other mechanisms behind most of those fasteners that must be removed as well.

The shaft slide out of the clutch body and gave me the gap.

The belt has to move around the cycle clutch release arm you can see just to the right of the gap. A bit of a twist to the belt and some pushing moves it so the belt can fit over the cogged pulley on the right. Below you can see it over the pulley.

The belt is pulled from the rear of the typewriter and fitted over the small cogged gear on the motor shaft. 

Replacing the shaft involves maneuvering it back to slide into the cycle clutch then replacing the screws and nuts on the plate. The nut has a post on its rear over which a spring loaded pawl sits. That pawl stops the print cycle shaft from bouncing a bit in reverse when a cycle ends, by falling into a notch on a cam to hold the shaft at its rest position. The pawl has a teeny circlip holding it onto the nuts post. 

Both screws thread into the frame, but one of them is longer and its threads extend on the rear to hold the selection stop plate. That is a plate that keeps the pivoting selection bar that twists and tilts the golf ball from going too far down. It is held by nuts on two screws - this one on the rear of the print cycle shaft plate, and one of the two screws holding the C2 switch plate onto the frame. 

The plate takes up a lot of the space available, thus there is very little room for a tool to put the nut on the threads.

At first I tried to use tape to hold the nut in place, backed out the screw on print cycle shaft plate and then engage the threads in the nut. That didn't work well so I switched to forceps to hold the nut while I turned the screw clockwise to catch the threads. 

With that started, I could fit a thin wrench in there to tighten it up. However, I had to get the other screw through the plate and install a second nut. The other screw is the right one of the two that hold the C2 switch plate in place.

Using the same technique - partially installing the screw, holding the nut with forceps and then turning the screw clockwise, I got the nut engaged on this second screw holding the stop plate.

You can see in the picture above that the stop plate keeps the more goldish looking pivoting mechanism from moving past a certain point. I will need to adjust the position of the plate, along with a ton of other adjustments, once I finish the reinstallation of all the parts. 

Once I replace the intermediate gear train, all the shafts are connected again. It is important that the three shafts are synchronized = the left shaft connected to the pulley, the print shaft that the carrier runs over, and the filter shaft that trips the space function at the end of a print cycle. These are several of the items1 to be adjusted, although I worked very hard to get the gears back together as close to in sync as I could initially. 

The print cycle clutch has a number of adjustments that must be made since it was also disassembled. The C2 switch has to be adjusted to open and close the switch contacts at the exact rotary positions during a print cycle - this blocks the 1130 from activating selection solenoids during the time when the type element is turning to position. I anticipate a good hour of fiddling to get all the adjustments required for the parts I had removed completed to my satisfaction. 

I did have one part that fell out during disassembly that I am struggling to identify so that I can reinstall it. 

I looked through every part on the parts manual for the typewriter but didn't see any candidates. The parts manual groups parts in diagrams based on their function, not their locations. Thus when looking at the selection mechanism diagram that has the stop plate I installed, you don't see the C2 switch assembly because that is on a different diagram. 

Finding parts that fit together in one location is not easy, since they can be spread across dozens of diagrams. However, I know it had to have dropped off when I was removing some screw or nut involved in the belt replacement. 

Looking at the thin material this is constructed of, we can see it isn't directly moving or handling force. We can see an elongated hole meaning that its final position is adjusted. There is a notch and a step on the end that must engage a rod or spring. These are all clues.

I have opened up the typewriter on my personal 1130 system and will be peering closely into every part of it hoping to 

Using CE Cartridge to align heads on IBM 1130 internal disk (13SD factor name, 2310 when in external cabinet)

THEORY OF THE ALIGNMENT TRACK AT CYLINDER 100

IBM recorded a 5 mil wide track that is all zero bits, but offset the recording mechanism so that the track is eccentric compared to all normal data tracks. Each track/cylinder is 10 mils apart, with the data ideally centered in that ring as the surface rotates under the head. The eccentric track moves about 2.5 mils either side of center, touching the outer edges of the ring at two points and being perfectly centered at two other points, all points being 90 degrees from each other. 

The head on the 13SD disk (the internal disk drive of the 1130, also called a 2310) has a read/write coil and an erase coil. The read/write head reaches each point on the track first, with the erase coil trailing behind. The width of the recorded pattern is wider than 5 mils initially, so the erase coil trims off the edges to leave the 5mil center. 

When using the CE cartridge to read the alignment track at cylinder 100, the read/write heads are disconnected and the erase coil is instead connected to the read preamplifier. IBM uses a special adapter that is a cable extension to swap the wiring. This means that the coil is only seeing magnetic flux at the two small poles that make up the tunnel that the normal signal passes under. 

Thus when the eccentric track moves towards one extreme or the other, it is mainly under one of the two poles. This produces a strong signal of one polarity or the other depending on which side of the coil the track is under. As the eccentric track returns to the nominal path in the center, the signal is in the tunnel and produces a minimal signal.

Thus, using an oscilloscope, we can watch as the heads are moved outward from before cylinder 100, gradually seeing a strong peaked pattern from the eccentric track. Initially peaks in one polarity are much higher than the other polarity but as the head is moved to the central position in the track, the two peaks should be equal heights. 

Theory

Directly on target position

About 60% offset from correct position

Vendors who built drives derived from the 13SD, such as DEC, Pertec, Diablo and others, usually moved to a higher density recording head. However, they still use the same alignment philosophy. Their versions of the CE packs have a high density eccentric track at cylinder 105 in addition to the standard density track at 100. 

They also worked out an interesting way to use the standard density track at 100 from an IBM CE cartridge to align their high density heads, by inserting a 5mil shim at a precise location on the cartridge to increase the eccentricity of track 100 (and all other tracks as well). This increased width made the signal peaks easier to read with high density heads.  

I can see that this might be a way to write an eccentric track on a regular cartridge to use in a pinch if one doesn't have an IBM CE cartridge available. 

SWAPPING LEADS ON DISK DRIVE ELECTRONICS GATE TO USE ERASE COIL

The leads from the disk heads are connected to pins on the backplane (SLT board) on the rear of the disk drive. By moving the leads around, the erase coil can be connected to the read preamplifier rather than the read/write head. This matches the function of the IBM alignment adapter tool.

HOOKING UP SCOPE TO TEST POINTS ON THE DISK DRIVE

The preamplifier circuits have an output at slot D3, pin B07 (also named D2 G07) on the backplane, which is hooked to an oscilloscope. It is set with the input at 500mv per division and the timebase at 5ms per division. The pattern displayed is used to adjust the arm.

LOOSENING THE CLAMP SCREWS ON A HEAD

The top head is 0, the bottom is 1. Working with one head at a time until it is aligned, we loosen its clamp screw and pull the arm out towards the spindle of the disk cartridge a bit. The adjusting screw for that head is preset to a depth of .188" from where it exits the bracket to its point. This is a good starting point for the head to be definitely to the left of the proper track position. The arm is pushed back to touch the adjusting screw and the clamp set to very light pressure. 

SPINNING UP CE CARTRIDGE AND ALIGNING THE HEAD

While watching the oscilloscope, the adjusting screw is screwed slowly clockwise which pushes the arm outward towards the cartridge spindle. The clamp should allow this to move the arm but not be so looses that the arm moves beyond where the screw tip would push it. 

When the signal looks correct on the scope, tighten the clamp screw while checking that the signal is still good. This may take a couple of iterations as the clamp screw can sometimes move the arm a bit as it is tightened which must be anticipated with the adjusting screw positioning of the arm. 

Turn off the drive. Switch to the lower head (1), loosening its clamp screw, pulling it out a bit and presetting the adjustment screw for the lower head to 0.188" depth. Push the arm back in and apply very light clamping. 

Spin up the drive and adjust the screw for head 1 until the signal will be evenly balanced when the head clamp screw is fully tightened. This finishes the alignment.

IBM 1130 typewriter (console printer) repair and adjustment - part 1

REMOVAL OF TYPEWRITER FROM 1130

The belt snapped so that the motor spun without turning any of the typewriter mechanisms. I had to remove the machine to replace the belt and perform some other fixes that were needed.

To remove the typewriter, signal and power cables must be disconnected from the SMS connector block down inside the 1130 and snaked out of the machine. 

The front panel of the typewriter holds the Console Entry Switches (CES), sixteen toggle switches that are read by programs to select options and used by the hardware to load certain registers. They limit how far the typewriter can be moved from the 1130 since the ribbon cable to the CES is not very long. 

I realized that I could unscrew the mounting block for the CES and have that flopping around near the 1130 while the front panel can be put back on the typewriter to support adjustment of the pushbuttons for tab, return and space. 

RESOLVING THE FAILURE OF SOLENOID DRIVEN SPACE FUNCTION

Using the hand crank, I tripped the space solenoid. The clutch on the operational shaft that handles space, backspace and tab should spin 180 degrees then stop - I verified that it did. The rotation of that clutch should pull down a bar at the rear of the typewriter and pull a linkage that is placed under the lip of the bar by the space function trip mechanism. 

That linkage is coupled through some parts to pull down on a lever that pulls the space torque bar before the claw pops off the torque bar end. The space after typing characters works, so the torque bar itself and related adjustments are good, however this is activated by a separate mechanism using a pull-rod from a cam which rotates in a print cycle. Thus space is done by two separate means, but the adjustments interact a bit. 

It didn't take long to get both working properly. The final test will be driven by the 1130 under power, but for now all looks good with spaces. 

ADJUSTING FRONT PANEL BUTTONS TO OPERATE SPACE, TAB AND RETURN

The buttons did not push far enough to trip the levers that push down on the function levers. These spring loaded levers are held forward but when pushed down they pull backwards to trip the operational clutch and to move the related function linkage under a bar that will swing down with clutch rotation. 

The first issue was loose screws holding the cable sheaths in place so the cable inside will pull down on the mechanism. In the picture above you can see the screws across the top. 

Next I had to adjust the levers that are behind the pushbuttons on the front panel, so that they pulled enough on the cable to trip the operational clutch latch. 

LUBRICATION WORKOVER TO IMPROVE PARTS MOVEMENT

I went over many points in the machine to flush out any stale oil and ensure the machine parts move freely. The operational shaft which moves continually under motor power was the first area of concern. I then lubricated all the parts that move with the operational clutch when a function is selected. 

Next up was the print cycle mechanism in the frame of the typewriter. I made sure all gears and bearings moved freely, as did the print cycle clutch and the shaft to its left. The space cam and shift lockout cam parts were also given attention as they move during the print cycle. The main print shaft that runs through the carrier and its bearings were checked for easy movement.

Up on the carrier, I lubricated all the parts that swing, rotate or slide to select a position on the typeball and to throw the typeball at the ribbon and paper. This took a while but I had to assure easy movement to lessen the load on the motor and belt. 

I then paid attention to all the linkages in the rear that implement space, backspace, tab, line feed and carrier return activation. These seemed a bit sticky since the tab and return operations weren't consistent when the diagnostic was printing status.

Next up were some torque bars and other linkages for the space and tab operations. The last step was to move around the machine looking for any other moving parts that weren't operating freely. By the end of all this work, I was satisfied with the lightness of the resistance for everything except carrier return. There is still quite a bit of force needed to drive the carrier back to the left. I will investigate more later. 

MISCELLANEOUS OOPS

I was working on the fit of the 2501 card reader hopper gear, a plastic ring I had printed to fit over an aluminum disk, replacing the IBM original plastic ring which disintegrated with age. The gear was designed with a recess for the disk to fit into, but the edge of the gear teeth on the side with the recess had bowed inward a bit. This made the fit of the disk quite challenging. 

As I was trying to get it to fit, I applied a bit of bending pressure against the bowing, but I ended up breaking the ring in half. I think I need to select a different material for this part when I have it made again.