Cleaning up the acrylic cover for the 1053 console printer and identifying another issue

COVER FOR 1053

The cover over the IBM Selectric typewriter mechanism that is the console printer for the 1130 computer has an acrylic cover on the lid, minimizing noise for the operator while allowing a view of the ball, paper and printed output. This acrylic piece had been snapped into two parts prior to my receiving the machine for restoration. Either someone tried to remove the cover but didn't know the proper way or it was struck by some heavy object. 

CLEANING UP THE BLUE TAPE LEFT OVER AFTER REGLUEING THE PARTS

I carefully scraped away as much blue tape from the glue joint edges as I could so that the cover was colorless rather than tinted with blue bits. It was a tedious process but is almost fully done.

ANOTHER PIECE OF THE COVER DISCOVERED TO BE MISSING

The way that the cover is placed on the 1053 is to slide it backwards on the lid so that tabs on the underneath sides of the cover push back on springy projections, then letting the spring push the cover forward to hold it in the lid opening. 

We can see in the picture above the tab on the underside of the cover that hooks onto the springy projection for left side of the typewriter. It is a sort of triangular shaped ramp under which the projections fit. The projections on both sides are below.

These projections bend backwards as you can see, so that as the cover is pulled to the front of the lid it bends the springs. The cover can be dropped down so that its rear fits into the opening of the lid, then the spring force pushes it rearward in place. 

However, in the picture below look at the right side underneath the cover, where the triangular sort of tab was snapped off. This piece was not provided to me, thus I will have to make a bit and glue it on to restore the functionality.

Site of missing tab within red circle

Various fixes to the IBM 2501 card reader and inspection of lower cabinet circuitry

STACKER GEAR A TOUCH TOO SMALL TO ENGAGE FULLY

The stacker mechanism that collects cards after they have been read uses an oscillating part to nudge cards together. This is driven by a cam that is turning slower than the main mechanism, with gearing to reduce the speed. The stacker gear on the axle of the cam has 211 teeth on an approximately 3" diameter gear, which meshes with a perhaps 5/8" diameter gear on the main motor shaft. 

The original part was constructed of a plastic which disintegrated with age, thus a replacement gear had to be fabricated. Experts at a museum in Europe had produced a design to be 3D printed, which I used. Because of inexact dimensions for 3D printed parts, the teeth of the new gear were not fully engaging with the teeth on the driving gear. Whenever the ramp of the cam is rising to push the nudger sideways, the resistance increased just enough so that the teeth skipped over each other.

Based on a recommendation, I picked up a rubber band of a suitable size to put around the diameter of the replacement stacker gear. This gave enough extra diameter plus some bite for the teeth of the driving gear, allowing the stacker gear to rotate smoothly and activate the nudger. I superglued the band over the teeth of the plastic gear. 

REMOVED FEED PRESSURE ROLLER TO FREE UP BEARINGS

With a card sitting in the pre-read station, when the controller logic requests a feed or read of a card, it activates a solenoid to lever a pressure roller down onto the rubber roller underneath. The card is pinched between the rollers and given a push into the read station. 

The pressure roller was not turning freely. I disassembled the parts, carefully oiled the sides of the roller and worked it free, then put everything back together. So far, we have the parts working correctly to move a card into some rollers at the hopper throat by moving picker knives at the proper time. The continually turning rollers in the throat moves the card into the pre-read station. 

roller that didn't

Solenoid to press roller down

As the card leaves the rollers it slides rearward to come to a stop on a spring loaded bar that ensures the card is in the correct position for its future movement through the read station. 

Bar at bottom

WORKING ON PRESSURE ROLLER IN READ STATION TO ACHIEVE EASY ROTATION

As a card is fed from the pre-read station to the read station, it enters a narrow gap and comes into contact with continually turning rollers that will move it steadily past the photocells of the read station. There is a rubber wheel on the underside and a spring loaded pressure roller on the top. 

Alas, the pressure roller bearings were also sticky. I added some oil and began to work the roller to get smooth movement so that it could uniformly move a card through the read station. I am not satisfied yet with the smoothness of the roller so I will continue to work on this next time.

Poor picture of sticky roller in middle

OBSTRUCTIONS IN THROAT OF READ STATION

I tried to slip some paper under the read station, having it pulled by the roller pair above, but the paper kept stopping on something. I imagine this is dust, rodent hairs and other debris, but I haven't yet cleaned it out. There is no value in having the pressure roller try to move a card if the pathway is jammed. 

SMALL CAGE FOR SLT CARDS SITS IN THE LOWER CABINET

The main circuitry in this cage deals with the photocells and the coils detecting the timing pulses. Amplifiers turn the light into well shaped pulses at two points within each card column, allowing the values detected to be compared by other circuitry inside the IBM 1130 controller logic. A mismatch is used to detect read failures. Other amplifier shape the timing pulses CB-1, CB-2 and CB-3. 

BEGINNING INSPECTION OF POWER SUPPLY AND POWER BOX

Underneath the reader mechanism sits the power box plus a card gate with SLT cards and some connectors. Otherwise it is empty. The power box sits on rails and is not bolted down any way. Instead it can be lifted upward and the bottom swung over the rail upon which is sits. 

The bottom of the power supply has rectangular notches that drop onto the red rail in the diagram above. The green flat plate at the top fits into vertical slits at the top of the power supply. Thus one can push the power supply up so that it nests all the way up on the green plate; this allows the bottom of the power supply to swing inwards over the red rail. Once it place it slides down to sit on the red rail. 

I do not have schematics for the power supply nor ALDs for the card reader, which could slow my progress depending on how the top level testing works out.

Capacitors to check

Transformers to check

Diodes and relays to check

Another view of capacitors

multipole relay

Motor contactor and switch

My first restoration tasks in the power box will be:

• Checking for shorts
• Testing all capacitors
• Testing all rectifier diodes

Once the major parts seem good, I will remove fuses and isolate sections so that I can test each portion of the supply individually. This provides some of the voltages needed but the IBM 1130 itself supplies the +3, -3 and +6 voltages for the SLT logic through the cables into the 2501. The cables also provide the AC voltage that spins the motor and energizes the remaining local power supplies. 

Preparing bumper parts for replacement foam in 2501 card reader

BUMPER ATTACHED TO TOP OF STACKER WHERE CARD STRIKES ON UPWARD MOVEMENT

The cards being ejected from the reader will curve inside this top piece of the stacker, striking a soft bumper at the end to arrest their motion and send them gently backwards. 

Bumper mounts to Allen bolts in circled area

BUMPER HOLDER PARTS REMOVED

The bumper consists of a plastic holder that fits under two Allen bolts on the stacker cover. There is a metal plate screwed onto the plastic, holding down a rubbery bumper whose remnants are visible in the picture below.

The substitute I am producing will be glued in place of the metal plate above. It is heavy insulating foam which will have Kapton tape applied to make the surfaces slicker where cards might have to slide. 

Repairing acrylic typewriter cover lid for VCF 1130

TYPEWRITER COVER CRACK WITH ACRYLIC GLUE

The lid of the 1053 console printer, an output only version of a Selectric typewriter, has an acrylic plastic part that is held onto the opening of the lid top. It allows the operator to see what the 1053 is typing but reduces the sound emitted and helps keep foreign objects from falling into the typewriter mechanism.

The VCF system's acrylic top that was cracked and almost broken in two. It had been stabilized by the use of scotch tape to hold everything together, but this is not esthetically pleasing. It has to be repaired or replaced.

I have a great acrylic glue which would bond the sides of the crack together. To make this repair and to keep from having blobs of glue disfiguring the surface of the plastic part, I had to devise a method of holding the parts together while the glue worked. 

I chose a very thin version of the acrylic glue to minimize the risk of marring of the surface. When I attempted to glue the parts together, I found that they didn't provide enough 'melting' to fuse the sides. It seemed to hold together as I let the glue set but it fell apart a few minutes together. 

I moved on to using cyanoacrylate glue (superglue). It forms a very solid bond with acrylics and I have good experience with it. The main risk is another form of marring of the appearance of the plastic, called fogging. Any glue that hits the surfaces of the lid, such as when squeezing out of the joint, will cause that spot to look as if it had been frosted. 

To address this risk, I had to combine two strategies. First, I had to put tape across the surfaces (other than the seam that is being glued) so that any glue that leaks out will not penetrate through to the acrylic underneath. Second, I had to orient the parts so that any dripping was down to the underside of the part when it was installed on the printer - this would lessen the visibility of any fogging that did take place. 

I can now appreciate the plastic films that cover acrylic parts from the supplier. This not only protects against any scratching but it could help prevent fogging when edges are glued together.

The sections glued together, although a bit of blue tape was stuck on the edge of the glue at the joint. I will come back tomorrow and carefully clean off the tape edges. 

The fracture line is still noticeable, although it will be less obvious once the blue tape remnants are removed. The thickness of the acrylic is enough that you can see both edges - top and bottom - of the fracture. In this picture below only one side has blue tape stuck to the seam. 

Restoration work on IBM 2501 card reader

REASSEMBLED TIMING DISK AND HOPPER SIDE MECHANISMS

The timing disk fits on the same shaft as the replacement hopper gear I built. The shaft also turns the cam that will move the picker knives which grab the bottom card in the hopper and push it into the rollers. The replacement hopper gear turns the rollers that will move the card into the pre-read station where it will sit waiting for a feed or read action. 

A woodruff key on the shaft ensures that the timing disk is oriented in sync with the picker knife cam. The timing disk has a permanent magnet glued to it, with one pole at the rim of the disk. As the disk rotates, the magnet passes three coils that are arranged around the outside of the disk. These coils produce timing pulses, which IBM calls CB-1, CB-2 and CB-3. 

A microswitch is deactivated by the weight of cards sitting in the hopper, but will turn on when no cards are placed there. This tells the controller logic when the hopper is empty. A card weight sits on the top of the card stack in the hopper, ensuring enough weight to keep the microswitch from activating as long as there is even one card in the stack. 

A protective cover was reinstalled over the timing disk and gear train, finishing the reassembly of this area. When I hand crank the reader, everything turns smoothly in the hopper area and by manually tripping the trigger for picker knives, I see then completing one cycle to feed a single card. Normally a solenoid trips the trigger under control of the controller logic. 

PARTIALLY REASSEMBLED STACKER SIDE MECHANISMS

I put most of the parts back together for the stacker mechanism, but may need to pull the top piece off when I am working on the new bumper. Cards are ejected at speed from the read station following an arc to convert horizontal to mostly upward motion. The card flies up to strike a foam bumper at the end of the top piece, arresting its motion and causing it to fall back down onto the nudger. 

The nudger has arms that oscillate left and right, urging the card that just fell to move against the leftmost part of the stacker. An upright arm slides on a shaft, spring loaded to the right, so that as cards are added to the stack the arm will gradually move leftward as the size of the stack grows. 

The nudger is driven by a second plastic gear I built as a replacement for the disintegrated original part. This turns a cam to cause the oscillation of the nudger arms. These now move freely left and right but the gear teeth are not engaging quite firmly enough; the gear turns most of a revolution but stops as the ramp on the cam is steepest. 

The solution proposed by some genius restorers in Europe who have their own 2501 is to put a rubber band like sleeve on the teeth. This increases the effective diameter just enough to ensure good grab and the teeth don't have to mesh perfectly because the rubber squishes between the opposite teeth to generate enough friction. 

When I receive the 3D printed part to replace the bumper inside the stacker and the rubber band for the stacker gear, I will complete the reassembly. Once they are installed then the rest of the stacker mechanism will be finished and working properly. 

STILL TOO MUCH FRICTION ON SLIDER INSIDE STACKER

The spring loaded arm that holds the card stack towards the right, moving to the left as the number of cards increases, is attached to a shoe on the bottom that moves over a long metal rod. The shoe has sliding surfaces on its top that move under guide rails on the edges, plus it moves over the rod. 

Due to corrosion from moisture and rodent exposure, both the rod and the surfaces of the shoe needed to be cleaned up and the bumpy surfaces removed. The parts are much better but the shoe is still a bit sticky. It should snap to the right under spring pressure and slide smoothly with minimum force as cards press against the arm. However, it has variable friction so that its movement is not even. Sometimes it will stop partially restored to the right rather than completing its movement. I need to work further on this to regain smooth operation. 

WAITING ON 3D PRINTED PART FOR BUMPER INSIDE STACKER

The original bumper was a bit of rubber attached to a plastic part, which was screwed to the top lip of the stacker top piece. The plastic disintegrated, much like the two gears had, thus it needed replacement. A 3D printed holder will be arriving soon, to which I can attach some thick foam with a surface layer of Kapton tape. This is a solution also developed by the team in Europe to restore their own 2501. I have the foam and tape already. 

IBM 1130 typewriter (console printer) repair and adjustment - part 9

AFTER ADJUSTING SHIFT INTERLOCK, RAN PRINTER DIAGNOSTIC

Once the shift interlock was working properly the typewriter appeared to be ready for a successful diagnostic run. I loaded the code into core and started the test up but began to see error messages - new messages that hadn't been observed before. These indicated that immediately after issuing the XIO Write instruction to print a character, the status sensed from the device did NOT show it busy, but it should have.

When printing a character, the only status line from the typewriter that matters is the -Twr CB Response signal which is produced by a series connection of three microswitches to feed +48V into the device controller logic in the IBM 1130. The switches break the circuit during three types of operations:

1. printing a character
2. performing a space, backspace or starting a tab
3. shifting between upper and lower case

Mostly the line is connected to +48V but drops to 0V when one of those operations above is underway. The device controller should mark the typewriter as busy as soon as it initiates those operations, then turn off the busy when the -Twr CB Response line returns to +48V when the operation is over. 

CHECKING THE MICROSWITCHES IN THE TYPEWRITER

I first verified that the three microswitches for the -Twr CB Response signal were working properly by manually performing those operations while observing the state of the signal with a meter. They were working as they should. 

I then checked the other feedback signal line, +Twr CRLFT Intlk, which is normally at 0V but has four microswitches in parallel that connect the signal line to +12V during Tab and Carriage Return/Line Feed operations. Those are both operations that take a long and variable amount of time to complete as it depends upon the number of columns that the carrier must move from its current position to the chosen column or left margin. 

For each operation type, Tab or CR/LF, two microswitches are used. One of them is active for one half turn of the operational shaft when the operation is initiated. The other remains active until the long movement stops. The overlap of the two microswitches ensure that +Twr CRLFT Intlk is on from the initiation of the operation until it completes, whereas each one alone either ends too soon or starts after a delay. 

My testing showed that all microswitches involved in feedback to the device controller logic were working properly. That left unresolved the cause of the errors I was receiving. In this case, it does not appear to be a typewriter problem, but instead an issue with the logic cards that implement the device controller. 

The machine has also sporadically halted with parity errors, which appear to be caused by the injection of spurious bit values on the input bus during an IO operation. This may be from the typewriter controller logic it could come from other device controllers or unrelated areas within the machine. These may be related to defective components that are producing the error picked up by the diagnostic, so it would be good to chase this down as I troubleshoot this newest issue. 

IBM 1130 typewriter (console printer) repair and adjustment - part 8

ADJUSTED COLOR TENSION FOR RED/BLACK RIBBON COLOR

A pair of solenoids on the left side of the typewriter (when viewed from the front) pivot a lever up and down to apply more or less tension to a thin plastic ribbon. The ribbon runs over pulleys with both ends hooked to the carrier. This allows the carrier to move from leftmost to rightmost column position with the ribbon sliding over the various rollers. 

The lever ends up pulling on a spring loaded mechanism inside the carrier that adjusts the lift height of the typewriter ink ribbon during a character print cycle. When properly adjusted the mechanism either positions the upper half or the lower half of the ink ribbon in front of the character being printed. 

The adjustment is the rightmost roller (when viewed from the front of the typewriter) which can be moved left or right to add or remove tension to the narrow plastic ribbon. With the machine under motor power, I typed characters while adjusting the roller. I set the left side lever to the black and then to the red position, watching the resulting typed color. 

RAN CONSOLE PRINTER DIAGNOSTIC BUT EXPERIENCING HANGS

Now that the ribbon color worked well and the tab interlock switch was functioning properly, I expected to have a successful run of the diagnostics. I loaded the memory image of the diagnostic into core and started it up. It began typing and tabbing well but then came to a halt with a wait code 30FA that indicates that the typewriter never cleared a busy condition. 

Using a continuity tester, I found the microswitch that was causing the busy condition. That switch is activated during a shift operation, moving the type ball between upper and lower case hemispheres. Shifting the ball significantly changes the tension on the rotate band; if a print cycle were to take place at the same time, it would simultaneously change the tension. The result might be a snapped metal band. 

What I discovered when looking at the typewriter was that it was partway through a shift operation. While the diagnostic was typing characters, it shifted the ball to get to a next character but the shift mechanism didn't finish its operation. 

There is a pawl that will block the mechanism from rotating when the typewriter is in the midst of a print cycle. The pawl was jammed into the teeth holding the shift cam from turning, but we were not in a print cycle. 

ADJUSTING THE SHIFT LOCKOUT MECHANISM

The shift mechanism is a circular assembly that stops in two spots 180 degrees apart. Solenoids trip the clutch allowing the shift mechanism to make the half turn to the other position. A ramp rising out of the plane of the shift assembly will pivot an arm with a roller that the metal rotate band moves around. The high side of the shift mechanism moves the roller out on the order of an inch. That added tension rotates the typeball to its other side. When the shift mechanism rotates to the side where the ramp is low, the roller moves back to release tension letting the ball twist back. 

A pawl will lower to block the teeth of the shift mechanism from turning, which will interlock the shift while a print cycle is underway. This is driven by a cam on the end of a shaft that turns during a print cycle. The pawl is held out of the way when the cam is at a high point but will rotate down to block the teeth on its low points, mid print cycle. 

The cam has two setscrews so that its position on the print cycle shaft can be adjusted. When the print cycle is not active, the cam roller should be riding on a high spot with the result that the interlock pawl is raised .030 to .060 inches above the highest tooth on the mechanism. 

The cam was in the wrong orientation so that the interlock pawl was just a bit too close to the teeth so that it can jam the shift mechanism from turning even though the print cycle has completed. I got out the allen wrenches and turned the cam to ensure it wouldn't jam up the shift mechanism. 

Next up - reload the console printer diagnostics and make sure that the typewriter performs everything properly. 

Cleaning and waxing of stacker mechanism for 2501 card reader

DISASSEMBLED AGAIN

Because their was too much friction and sticking, I pulled everything apart to work on the parts. My first attempt using 409 did not remove enough of the deposits to allow free and easy movement of the parts. There was also a shaft around which the cam roller and levers turn in order to move the card shifter left and right, but it was barely turning because of sludge inside.

PUT RUSTED/CORRODED PARTS IN CONCENTRATED VINEGAR AND SCRUBBED

All the parts that were interfering with smooth movement due to layers of rust or corrosion were soaked in a 30% vinegar bath for hours to loosen up and dissolve what it could. I used a sanding block to break away the surface coatings. I was able to reduce the irregularities in the surfaces far enough to allow the parts to move smoothly. 

APPLIED PASTE WAX TO REDUCE FRICTION IN CARD SHOE AND ROD

After the rust and other dirt was removed from the rod, it still had some rough surfaces because of corrosion pitting. I used an automotive type paste wax to reduce friction on the rod. I had cleaned out the hole in the shoe as well. 

In addition, the surfaces that the shoe glides upon - the side plates in the reader plus the top of the shoe - were waxed to give it less friction. The result was an acceptably free card holder sliding to the right under spring tension but giving way to the left as cards are added to the stack. 

GREASED THE SHAFT ACTIVATING THE CARD SHIFTER

The shaft with the cam roller and levers pivoting on it needed a bit of grease applied in order to have the parts rotate easily on the shaft. This is far enough down that there is no risk of the grease contacting any cards, thus it was safe to lubricate here. 

IBM 1130 typewriter (console printer) repair and adjustment - part 7

BENT HORIZONTAL LUG FOR TAB INTERLOCK SWITCH

The objective with the positioning of the horizontal lug is to allow the tab trigger lever to maintain a small space between the latch lip on the lever and the tab torque bar, so that the tab trigger lever will positively catch the latch lip when the torque bar first rotates. It must also keep the trigger latch lever pushed down enough to keep the tab interlock switch activated until the tab torque bar returns to its full rest (vertical) orientation when tab movement ends at the target column. 

I held the tab torque bar so it didn't rotate and applied bending pressure to the horizontal lug until it satisfied the conditions above. The first testing was with manual rotation of the typewriter using the hand cycle wheel, both slowly and with a quick acceleration at the start that had previously always caused the interlock switch to reset. 

This worked, even with a rapid twist of the hand cycle wheel. I then applied power to the IBM 1130 so the typewriter motor was spinning and did some tab activations using the front panel tab pushbutton. The Tab Interlock Switch was clearly active for the entire travel time of the carrier until it reached the destination tab and stopped. This works properly now. 

Cleaning up the stacker mechanism

REMOVING CRUD AND CORROSION ON PARTS

Most of the brown caked crud on the parts, which looks like rust, is actually a mix of mouse urine, dirt and a bit of aluminum or other metal corrosion rather than iron oxide. I was able to remove much of it with 409 spray and in some cases a mild sanding block to break free the layers. 

Example of corrosion

The rod that the card stacker shoe slides along cleaned up quite nicely. With a bit more work on it and some cleaning of the side plates that the shoe slides underneath, I should get it to return rightward under spring tension and move freely. 

MORE DISASSEMBLY IN ORDER TO CLEAN AND LUBRICATE CARD PUSHER PARTS

I removed the metal arch that converts the card motion from horizontal to vertical as it enters the stacker. This gave me good access to the card pusher plates that should oscillate smoothly left and right to move cards leftward to join the stack of other cards. 

I did a trial assembly after the cleanup and lubrication and found that everything moved reasonably well, but still had some resistance that kept the return spring from always pulling the card pusher plates rightward. The cam which causes the pusher plates to oscillate will move the plates leftward at its high spot but when the cam profile lowers, the spring must move the plates rightward to ensure smooth back and forth action. 

Pivot driven by cam moves card pusher back and forth

Shoe at bottom sliding on the rod

WORKING ON EASY MOTION WITHOUT ADDING OIL

Normally with mechanical parts I would add some oil or grease to reduce friction and ensure smooth motion. However, the stacker parts can come in contact with the punched cards. Since they are made from paper they will wick up some of the oil. 

That would cause the card to swell up. The throat in a card reader that allows just one card to enter at a time is based on the nominal thickness; a card that is too thick will jam up and bend. 

Therefore I have to find a way to reduce friction without the oils. I will use a combination of paste wax and more work removing sludge and corrosion from the moving surfaces. 

DISINTEGRATED BUMPER THAT MUST BE REPLACED

Below you can see the broken fragments of the bumper that the cards will fly up into and come to a stop. Fortunately I was warned about this and already have a replacement part in the works. 

The sound deadening foam that was glued between the ribs above has disintegrated. This is pretty typical of the foam used in 1960s IBM gear. I will remove it since it has no functional role, simply reduces sound levels. 

DISCOVERED MY ISSUE WITH HOPPER GEAR ALIGNMENT DOESN'T EXIST

In prior posts I was concerned about the timing between the picker knife actuation cam and the timing disk. The solenoid for the knife is triggered at the time of the CB 3 pulse from the timing disk and released at CB 1 time. This timing also starts the card feeding from the pre-read station out through the read photocells and into the stacker. 

I was worried that if the knife moves at the wrong time when the previous card hasn't cleared the pre-read station, we could have a jam. I wanted to get a copy of the FE Maintenance Manual to learn how to mesh the gears for proper synchronization.

However, that was due to a big misconception of mine. It appeared that the gear with the timing disk on it was meshed to other gears that not only turns rollers to move cards but also turns a cam to move the picker knife. Thus, the two gears would have to be set in the proper relationship in order to turn the cam at the right time. 

The diagrams in the Parts Catalog appeared to match that assumption. However, as I disassembled the card reader I realized that the cam for the picker knife is on the SAME shaft as the timing disk. The shaft has a key that orients the timing disk to the shaft, thus the timing between feed and pickerknife are assured. 

DRILLED OUT AND REPLACED A FROZEN RUSTED SCREW

As I was removing side plates to get access to the card stacker shoe and rod, one of the screws was too rusted in place to turn with a screwdriver. It was a recessed head screw as well, thus harder to apply turning torque to the end of the slot. I had to drill out the head in order to get the screw turning. 

Fortunately, it was a pretty standard type of screw that I could buy and use as a replacement when I reassembled the stacker assembly. 

Alerted to another plastic item on 2501 card reader that has failed with age

BUMPER STOPS UPWARD CARD MOVEMENT AS IT IS EJECTED INTO STACKER

As cards are fed through the read station, they continue to the left and curve upwards to be ejected out into the stacker. The card strikes an elastic bumper that arrests its movement and allows it to fall downward gently. 

The card pusher oscillates left and right at the bottom to gently move the card leftward until it is against the stack of cards previously ejected. The stairstep shape of the card pusher initially places the ejected card higher than the top edge of the stack, but then nudges it down the steps while the card slides down to end up well aligned against the other cards in the stack. 

WARNED TO CHECK THE CONDITION OF THE BUMPER

The bumper is another of the materials IBM used in the 1960s that degrades with the passage of time. Foam insulation, rubber and plastic parts outgas the chemicals that provide the elasticity and other characterists, so that by now they are brittle, crumble or in some cases have turned to a sludge. 

It sits in the area marked A in the diagram below at the top of the stacker assembly. The card flying up from below will bounce to a stop off the bumper, then drop to where the card pusher can move it against the other cards. 

The bumper itself consists of a holder (61), a soft elastic material (60) and a tougher outer face (62). 

EXPERTS WHO RESTORED A 2501 IN EUROPE ALERTED ME TO CHECK THIS

Friends who have restored 1130 systems for a museum had previously restored the 2501 Card Reader as part of that effort. They encountered the broken plastic gears during that work and were the source of the design files I used to fabricate my replacement parts. 

The found that the bumper on their reader was cutting or damaging cards because of its degraded state, so they replaced it. Because of this, they warned me to check the bumper on my 2501. The bumper was sitting there seemingly good but when I touched it to check the elasticity, it broke apart. 

Fortunately, the team had produced a design file for the bumper holder onto which they glued some firm foam. I was given the file and will build the holder. I already have suitable firm foam to add to it. 

2501 Restoration - mainly working on stacker section

VACUUMED OUT THE 2501 CARD READER

I used a shop vacuum to remove the fragmented plastic gear reside, mouse hair, dust and other junk from the card reader as the first step in cleaning it up. I will follow up with 409 and Simple Green for general cleaning. There is rust on a number of non-critical parts that I will partially sand and then treat with a rust converter but not right now.

STACKER ASSEMBLY NEEDS TO BE DISASSEMBLED

The card stacker is a mechanism into which cards are ejected at the end of a read/feed operation that will hold them in a neat stack for eventual removal by the operator. The card flies up and bounces off a bumper at the top to arrest its motion, then is nudged leftward by an oscillating assembly to result in the card fitting against the prior cards in a neat stack. The stack of cards is on a slider which is spring loaded so that it moves leftwards as the stack of cards grows until it reaches a 'stacker full' microswitch that causes the reader to become not ready. 

The slider moves along a chromed rod, with a shoe fitting under guide rails and having the rod pass through a hole in the center.  A spring attached to the shoe pulls the slider rightward. The chromed rod has rust and corrosion on it, so that the slider can't easily move left or right. This will need to be treated to allow easy movement of the rod through the shoe. 

The oscillating assembly that nudges cards to the left once they fall down from the bumper is jammed. It consists of a base plastic piece with steps formed into it, plus two thin plastic pieces that move left and right in slots cut into the base piece. The thin plastic pieces are moved by a lever underneath that is oscillated by a cam on a shaft. The shaft is turned by the stacker gear that I replaced, converting rotary motion into the back and forth nudging action. The thin pieces don't move due to solidified grease and dust. 

I have to remove quite a few screws and plates to open up the stacker assembly to remove the slider rod as well as to reach the thin pieces where they are frozen in place. This is mostly done now, but I need a bit more work to uncover the front side thin piece because the card reader motor is in front of it. 

Once I clean up the rod and the thin pieces, I have to reassemble the stacker. A number of the parts have room for movement so that they can be adjusted to specific widths or relative positions. In particular, the path that the ejected card moves through, as it moves up to the bumper and falls down onto the nudging assembly, may have a target range of adjustment.

I do not have access to the IBM 2501 Field Engineering Maintenance Manual, the document in which IBM would detail all the adjustments and specifications for reassembling parts of the card reader. This worries me as I will be doing even more disassembly of the reader, with those parts also having specific adjustment targets. If anyone knows of someone with this manual, such that I could get it scanned, it would be a great help. The parts catalog and FE Theory of Operations are available online already, but not this key manual. 

I will clean the rod, then sand down any high spots and finally try a rust converter to produce a smooth enough surface for the shoe to slide over it easily. The rod has a notch in it at the right for a circlip that holds it in place in the assembly, so simply buying a replacement rod of the right diameter and length isn't enough. 

Determined how to mesh geartrains in 2501 card reader

CONTINUOUSLY RUNNING SHAFTS AND SOLENOID CLUTCHES

The IBM 2501 Card Reader has a motor that is spinning continuously while the device is ready for card moving and reading operations. A number of drive belts connect different shafts both side to side and front to back in the machine to provide energy to various rollers and other devices.

The card stacker where cards are ejected after reading is connected to one of these shafts and via a cam converts the motion to side to side movement of the bottom of the stacker. This helps move each newly ejected card to the left where it can fit closely against all the cards that were previously ejected. 

Rollers to move cards from the pre-read station through the read station and push them up into the stacker also run continuously. Most of these rollers have a spring loaded roller on the other side such that the cards will be moved.  Any card entering between a pair of rollers will be grabbed and moved leftward. 

At the rightmost side of the machine in the pre-read station, however, the first roller does not have a counterpart permanently pressing on it. Thus the card will not be moved from the pre-read station until a feed solenoid moves the counterpart roller down to pinch against the card. When pressed down, this roller starts the card moving until it enters the next pair of rollers where the pair are pressed together to keep the card moving. 

The input hopper for cards yet to be read has pairs of rollers turning just inside the opening into the reader. As long as the cards sit stacked in the hopper they are not yet touching the rollers so they will not move. A set of 'picker knives' move front to back when activated by a hopper solenoid. These have a lip that is less than the thickness of a punched card, so they only push on the bottommost card. The entry into the reader has a 'throat' that is adjusted to be less then two cards in thickness, thus ensuring that one and only one card enters per movement of the picker knives. 

A row of 12 photocells sit inside the card path so that they will sense light coming through punched holes in each column as it is moved past. Cards sit in the hopper with the face of the card down and the left side (column 1) of the card to the left in the hopper. 

READING CARD IN PRE-READ STATION

Activating the feed solenoid pinches the card in pre-read so the continuously turning rollers propel it leftward into the next set of rollers. The card moves under the photocell station where each of the 80 columns can be sensed in turn, then moved up into the stacker. 

Simultaneous with feeding a card to read it, the hopper solenoid is activated to feed in the next card from the hopper into the pre-read station where it can wait for the subsequent read request. 

FEEDING CARDS FROM HOPPER TO PRE-READ STATION

Firing the hopper solenoid will cause the picker knives to push a card into the throat, where the rollers will push the card to the rear so that it stops in the pre-read station. When the machine is initially empty, a feed cycle must be taken to put the first card in pre-read before the card reader becomes ready for operations. This is done by pushing the Start button. 

Every read operation (feed solenoid) also activates the hopper solenoid so that as long as there are cards left in the hopper it will have one ready in pre-read at all times. When the hopper becomes empty, there is still a card sitting in the pre-read station from the prior picker knife activation. The card reader will drop out of ready condition at this point, allowing the operator to add more cards to the hopper if desired. When new cards are in the hopper, pressing Start will turn on ready, read the card in pre-read and pull in a new one from the hopper. 

However, when there are no more cards to be put in the hopper, the reader has not yet read the last one since it is sitting in pre-read. Pressing the Start button without adding any cards to the hopper will turn the reader back to ready where another read request can be processed to read that final card. A special condition is raised so that the 1130 software can tell this was the 'last card' being read. 

KNOWING WHEN TO SAMPLE THE PHOTOCELLS FOR THE 80 CARD COLUMNS

The rollers pulling cards through from pre-read to the stacker move continuously, as does an 'emitter station' in the machine. When the leading edge of the card enters under the photocells, the logic detects that at least one row (actually all 12) is dark. It records pulses on the emitter station, spaced one card column apart as the emitter station rotates. 

Thus each pulse identifies the location of columns 0, 1, 2 . . . 80, 81 and then the trailing edge of the card. After the card exits the read station, the emitter station is erased to be ready for the next incoming card. Because the pulses are placed exactly as the card first enters the photocells, we have a precise start position for the card. Because the emitter station rotates in synchronization with the rollers moving the card along, the pulses mark off the location of columns very accurately. 

TIMING CB PULSES SYNCHRONIZE CARD MOVEMENTS AND SOLENOID ACTIVATIONS

A rotating disk with a permanent magnet glued on it spins continuously as the reader motor runs. It has three coils placed around the perimeter so that the magnet will generate a pulse from each in turn at specific points in the rotation of the disk. These are called CB, for circuit breaker, which is an IBM term for a circuit that is turned on or off based on motion of a cam or other mechanism. 

The three CB pulses control when the solenoids are activated, when the emitter station pulses are recorded and thus relate to the movement of cards through the machine.

The solenoids are activated at CB3 time and released at the start of CB1. Cards entering from the hopper will slide rearwards into the pre-read station near the end of a cycle. A photocell to detect whether a card was feed into pre-read is activated at around 211 degrees, we after any card moving out of the pre-read has passed fully through the photocells. 

A card being read (by activating the feed solenoid) will have its leading edge enter the photocell station around 15 degrees, as it moves rightwards, meanwhile the card from the hopper is moving rearwards at the same time. The trailing edge of the card clears the photocell station around 165 degrees, thus the entire card is out of the pre-read station sometime prior to that. The incoming card from the hopper is about halfway into the pre-read station (based on the location of the photocell that senses it) at 211 degrees and will be at rest and ready for feeding before CB3 at 335 degrees. 

This is a ballet of simultaneous card movement that must be managed lest the incoming card from the hopper jams into the card moving through the photocells. The activate time of the solenoids runs from CB3 of one rotation to CB1 of the next, which starts the movement of both cards. Thus most of the synchronization is purely done by using the CB pulses to control solenoid firing.

However, the card that comes in from the hopper is fed through the throat by the picker knives. The solenoid to release them is fired based on the CB pulses, but the physical back and forth movement is driven by a cam that is also rotating continuously along with the timing disk. If the knife moves early the card might crash into the card leaving the pre-read station. If it moves late, the card might not be fully at rest in the pre-read station when the feed solenoid is activated to start the card through the photocell station. 

A gear on the timing disk meshes with other gears that turn the picker knife cams. Thus, the relative position of the cam to the timing disk is important to ensure that we time the picker knife movement properly. 

The Field Engineering Maintenance Manual would contain the instructions for setting the gears in time with each other, but that manual is not available to me nor available online. Fortunately, there is a blurb in the Theory of Operations manual that tells me how to synchronize these.

MY PROCEDURE

I will disconnect the new white gear from the gears on the right, then rotate the motor so that the permanent magnet pole (red arrow below) will be positioned at the CB3 coil (green arrow below) when the disk and new white gear is reinstalled. Then I will turn the existing gears so the cam is in the position show in the diagram above. Meshing the new white gear to the existing gears in this orientation will give me the relative timing necessary for proper operation. 

Trying gears on 2501 reader; narrowing down failure point on typewriter tab interlock switch

GEARS INSTALLED, TURNING WELL

The glued together plastic gears and aluminum disks were installed into the 2501 card reader. The teeth mesh properly, not too loose and not too tight. I left the bubbled up Gorilla Glue since it doesn't interfere with the operation of the gears. 

Stacker reduction gear for joggling cards

Hopper gear to synchronize picker knife with reader timing

FAILURE POINT IDENTIFIED ON TAB INTERLOCK SWITCH MECHANISM

The failure I am seeing is that the tab interlock switch can turn back off as the tab movement was initiated, well before the carrier actually reaches its destination column. The torque bar remains rotated during the movement, but the switch itself turns off.

After careful study I believe it is caused by misadjustment of the horizontal tab on the end of the tab torque bar. This allows the trigger lever for the tab interlock to move up and latch on the torque bar mechanism, when it should be held below the lip on the torque bar end so that it can't latch while the bar is rotated. 

In the diagram above, you can see that the horizontal lug of the torque bar allows the tab switch trigger to ride up so that its lip can latch atop the tab torque bar. As the torque bar rotates clockwise about 20 degrees the tab switch trigger lip is pushed off the torque bar and is moved down by the lug. That causes the switch to be activated. 

The horizontal lug should keep the tab switch trigger down so that it keeps the switch activated. The crudely modified diagram below shows that situation.

Because the horizontal lug is way too high over the tab switch trigger, it allows it to pop up and latch while the torque bar is still rotated. The adjustment is done by bending the horizontal lug down so that it matches the clearance shown in the first diagram. 

MY NEW KNEE

Front and left view of my new knee.