Debugging issue with XIO Sense DSW - part 1

BACKGROUND FOR UNDERSTANDING THE SENSE DSW ISSUE

The 1130 has a common input bus for I/O data as well as the device status words, with all the sources for a bit tied together so that any one of them can pull the line to ground to indicate a 1 value. This means that many circuits can be turning on those bits. 

When reading from a peripheral, the IO bus is gated into the B bus (memory data register or storage buffer register) at the correct time so that it is written back to the current memory word. DSW status bits are also gated to the B register in the same way. 

This means that the issue could also be occurring in the B register, but the IO bus value was correct. That is another avenue to chase down. In addition, there are other registers involved, which I will discuss below. 

The 1130 is a memory centric machine, with instruction execution involving one or more memory access cycles. An address is placed in the M register (Storage Address Register) before the cycle begins and the contents of memory are placed into the B register (Storage Data Register) in the midst of the cycle. If a new value is to be written into that memory location, the B register is changed before the second half of the storage cycle takes place.

The instructions themselves are in memory, thus before they can execute they must be read with a storage access. Each memory/storage access cycle is one of a number of defined types. I1 is what fetches the first word of an instruction, but we could need an additional storage cycle I2 if it is a doubleword instruction. 

The address of the target of the instruction must be determined and these might require storage access cycles themselves - IA for indirect addresses and IX if an index register is involved since those reside in memory at fixed addresses. 

Once all the preparation steps, at a minimum I1 but as much as four cycles I1, I2, IX and IA, then the purpose of the instruction can be satisfied by execution memory cycles. E1 is the first execution memory cycle, where a value might be fetched from memory or placed in memory. Some instructions may not access the memory, instead changing arithmetic or logical data, but that occurs using a storage cycle but setting a signal that suppresses access to the core memory during the cycle. 

We see the I register (Instruction Address Register) is moved into the M register before a cycle to cause the instruction's first word to be read into the B register. In the diagram above, a simple instruction has only the I1 cycle and then the E1 cycle to grab the value in the target memory location and place it in the B register. 

In the 1130, every memory access produces a value in the B register. When executing the XIO Write instruction, the last memory location we read is the address where the character we want to print is stored, thus B contains that value. When it then starts to execute the XIO Sense DSW (step I1), the first memory address read is the instruction word, which replaces the B register. The XIO step E1 then fetches the second word of the Input Output Control Command (IOCC) which has the device, IO function and sometimes control bits. Thus word 2 of the IOCC is in the B register. 

In step E2, the XIO fetches the first word of the IOCC which often is an address but for XIO Sense DSW the storage read is blocked and we instead just gate the IO bus to B register. The XIO Write, step E3, on the other hand, will fetch memory at the address we just picked up. For an XIO Sense Device, the value in the B register is then gated to the D (Arithmetic Factor Register AFR) and passed through to the A (Accumulator) register using a couple of arithmetic logical unit control signals. 

Somehow the value in the B register looks more like an XIO Write than an XIO Sense Device. However, the first word of the IOCC I used was not the address where the character value was stored, so it could NOT be actually reading it from memory like an XIO Write E3. 

The data that was in the B register multiple memory fetches ago is now showing up in the A register during the XIO Sense DSW step E2. While it looks as if the IO bus for the sense DSW stored the 'saved' value in B, it had no path to make that transfer happen. I think instead this has to do with the D and A registers. They would not be disturbed by the I1 and E1 stages of the XIO Sense DSW instruction execution, thus anything in them would remain there. 

The problem with this hypothesis is that the XIO Write should NOT be transferring the B register value to D or A. In order for the observed actions to take place, the XIO Write would have to transfer the B reg value somewhere else, which it shouldn't, then the XIO Sense Device would have to move something other than the IO bus value to B, D and A. 

Compare the XIO Write instruction, which is diagrammed above, with the XIO Sense DSW instruction diagrammed below. 

The E1 step of XIO Write will grab the second word of the IOCC and store it in the U register to determine which device and XIO function is being performed. The next storage cycle, E2, will grab the first word of the IOCC which contains the address in memory where the character data for typing is stored. That address moves to the M register and the E3 storage cycle causes the character value to be fetched into the B register. The typewriter controller logic looks at the value in the B register to determine how to control the typewriter. 

The E1 step of XIO Sense DSW also grabs word two of the IOCC, and another storage cycle takes place as E2. However, the storage access is blocked, nothing goes in or out of core memory. Instead, the typewriter controller logic sets bits to 1 in the IO bus and it is gated to move into the B register. Other signals than gate the movement of the B register to the D register (Arithmetic Factor Register) and control signals cause the value in D to move into the A register (Accumulator). All those gated moves happen during a storage cycle but no actual memory access occurs during that time. 

The address in the first word of the IOCC for XIO Sense DSW may be moved to the M register but it is ignored since we have inhibited memory access. The typewriter controller logic is only able to set some status bits in the IO bus. It is not able to write back the entire character value. This is the root of the problem - A register ends up with a value that is long since gone from the B register when XIO Sense DSW starts executing and the controller logic has no way to write it back even if it had it. 

IBM 1130 typewriter (console printer) repair and adjustment - part 10

USING SCOPE TO VERIFY BUSY CONDITION FROM TYPEWRITER

I could clearly see the -Twr CB Response signal drop during the typing of each character, although the console printer diagnostic as reporting that the DSW did not show the typewriter busy when it was sensed immediately after an XIO Write was executed. 

There could be a failure in the controller logic inside the 1130 system that is failing to indicate the busy condition. This is set when the XIO Write instruction is completing and cleared by the -Twr CB Response signal having gone low for a while and then returning to high. When the signal returns to high, besides turning off the busy signal it also requests an interrupt on IL4, presenting Operation Complete status.  

HAND CODE TO ISSUE XIO WRITE AND XIO SENSE DSW IMMEDIATELY AFTER

I set up the machine so that when the interrupt arrives on IL4 when the typing completes, the machine simply waits. Then, the code that fires off the character typing has a sense DSW immediately, stores it in a chosen memory location and at the end waits.

I could see that the Accumulator, as well as the chosen memory location, contained x3C00 which is not correct for what should be happening. This is why the diagnostic complained. I was suspicious because the value happened to match the character I asked to type - x3C is an A - so I altered the character I was typing to J (x7C) and that value was now returned for the  Sense DSW.

This should NOT happen.  This is not a typewriter issue, so I will blog about this under a new title and once it is resolved I can go back to documenting the console printer repair and adjustment. 

Wrapping up testing of 2501 card reader power supply box - one bad component discovered

INVESTIGATED THEORY ON HOW TRANSFORMER PRIMARIES ARE CONNECTED

My speculation on how the US transformer might be connected to the five terminals of terminal block PSTB1 was validated. I isolated windings and measured DC resistances. I removed the jumper between terminals 2 and 3 which did indicate there are two sets of primary windings, as I suspected. 

I altered the configuration to 230V, to match my workshop, and reverified the output voltages delivered. Since the transformer is ferro-resonant, thus crudely self regulating, the differences in the voltages produced were less than the delta from 208 to 230, but they did move in the correct direction. 

TESTING MOTOR CONTROL CIRCUITS

The motor is started by activation of the contactor relay K1, based on the signal -Motor Relay coming from the 1130 system controller logic. This works by grounding the input signal, thus powering the coil to switch on the contactor. I connected and disconnected ground to terminal 10 of PSTB2 where the signal arrives. The contactor clunked in and out based on the connection I made. A VOM confirmed the conductivity of the contacts when K1 was activated.  

As the power for the motor is applied via K1, it is connected to the normal winding of the motor. The starter relay K2 connects the start winding through an R-C link to shift the phase of the AC, sufficient to start rotation of the motor. Relay K2 has a time delay then switches off the start winding. I did not test this yet as I need to connect the motor first. The current draw of the motor starting is more than my bench 240V supply can deliver, thus I need to replace the PS box in the card reader and hook it up to the IBM 1130 in order to test the last piece - startup of the motor. 

Relay K3 is a time delay which delivers a signal back to the 1130 controller logic -Motor Hold that indicates that the motor should continue to be powered by asserting -Motor Relay. The relay is activated by relay K4, which switches on for each -Execute command from the 1130 controller logic. Execute is issued to feed or read a card. 

The relay K3 coil is provided with 24V from the brief activation of relay K4. The 24V charges a capacitor which continues to hold the coil activated but an RC network is draining the charge. The timing is set up so that the coil of K3 will drop out after about 15 seconds - as the voltage declines below some threshold. 

Thus, each time a card is read or fed, the hold relay activates for 15 seconds and causes the controller logic to hold K1 active so that the motor runs. During normal reading of a deck of cards, relay K4 resets the hold relay K3 repeatedly so that the motor is running continuously, but after any pause of 15 seconds the motor will stop. 

I tested relay K4 by connected terminal 9 of PSTB2 to ground, as this is where the -Motor Relay signal is connected. Each time I did the relay switched and the VOM indicated a good conductivity for the contacts. 

TESTING K3 FAILS

That would have also validated relay K3, as it will receive 24V every time K4 switches. I didn't see or hear the relay switching. I hooked the VOM to the contacts to see if it was working, but nothing changed. I then hooked up the VOM to the coil of relay K3 to see what voltages it was seeing.

It was presented with 24V when K4 activated and ebbed so that after 15 seconds it dropped to about 3V where K3 probably would have dropped out. However, no action and the voltage should have dropped across the terminals due to the current flowing through the coil.

I then used the VOM to test the resistance of the coil. Infinity! Open circuit. The wire entering the wrapped coil was good on each side, so the break is somewhere inside the coil of the relay. The part is a Sigma 41 F-98326 - a single pole dual throw relay with a 28V coil with the ability to switch 2A at up to 75VDC. 

This is excessive given it is just grounding a single line going into an SLT card in the 2501 card cage - it is pulled up to about about 20V when the relay is open and pulls that to ground when activated with just a few milliamps of current flow. Finding a substitute just has to support contact operation at milliamps of current with a voltage under 30V. 

LOOKING FOR REPLACEMENT RELAY

I partially disassembled the relay thinking that if I could find another Sigma relay with a 10K coil I could swap them. 

I checked eBay and did google searches, but nothing matched the exact relay. I can find many Sigma relays with similar specifications. There were plenty with contacts rated at 7.6VDC, 16VDC, or 22VDC but I need to have one at least 28V rated since it is looking at 24V or a bit more. 

The other issue is the resistance of the coil - which determines how much it drains the voltage on the capacitor in the time delay circuit. The schematic indicates this is a 10K ohm coil, however the relays I am finding on ebay are 1K or 2.5K typically. 

I found a Sigma relay with a slightly different form factor and current rating. This was also a 28VDC coil, 9000 ohms which will activate at 2.4 ma which is below the 24VDC level presented by the closing of relay K4. Thus it will activate and its current draw is only 11% higher than the nominal part. The contact is rated at only 1A but that is well above our maximum draw. 

It doesn't mount the same way, but I can work up a mounting method inside the PS box. I will buy this and verify it works properly when wired into the circuit. 

REMAINING TO TEST

I need to test the motor and its start relay K2, but that has to wait until the PS box is back inside the 2501 card reader cabinet. I feel pretty good about the condition of the PS box and the card reader. Once the time delay relay K3 is replaced I can move on with my testing. 

More on differences between US and European versions of 2501 card reader (model A1/A2) power supply

THE OBVIOUS FIRST

The mains voltage and frequency are different between the two geographies, which leads to the need to change the transformers and some attached components. Due to the magnetic saturation characteristics of the iron core in the transfer, the size and design varies based on frequency, with 50Hz transformers generally larger than their 60Hz counterpart. 

In the US, the mains frequency is 60Hz and the voltages one might encounter are 115V, 208V and 230V. Buildings whose supply is three phase would generally provide 208V as the phase to phase voltage, whereas single phase (residential style) utility connections provide 230V and 115V. 

In Europe, mains are more standardized at 220V but there is an acceptable range above and below, thus the need to adjust for mains voltage as low as 195V and voltages above 220V as well. 

The transformers IBM uses in their mainframes supported machines attached to all of the usual US voltage levels, thus they had taps for 115V, 208V and 230V which were configured during installation to match the building mains voltage. The transformers used in European machines generally had taps for 195V, 220V and 235V instead. 

CONFIGURING TRANSFORMERS DIFFER BASED ON REGION

Given the difference in the transformers installed in the machines between regions, the terminal blocks where the installer would configure the voltage change. Making this even more complicated, the transformers used by IBM might have more than a single multitapped primary winding. In that case, jumpers would connect parts of the two sets of windings so that the net magnetic drive was appropriate for the target voltage. 

Below is a transformer inside the IBM 1130 is wired for 115VAC input, along with the chart that describes the wiring needed to configure for 115, 208 or 220V.

Below this is the European equivalent of the same transformer in the IBM 1130, shown wired for 195V with its chart. 

This explains the wiring diagram for the European version of the 2501 model A2, which used terminals 1 to 4 on PSTB1 terminal block. Unfortunately, the actual connections show that it uses five terminals, similar to the US dual primary winding transformers, and couldn't just implement the chart just above for 115, 208 and 230.

SPECULATIVE WIRING OF US TRANSFORMER TO TERMINAL BLOCK PSTB1

My first guess at the connections of the transformer primary windings to terminals 1 to 5 is below. This matches the US transformer type from the US IBM 1130 and would be consistent with the jumper between terminals 2 and 3. 

In order to validate this guess and make a change to 220V, I will disconnect the terminals and measure resistance to try to verify (or disprove) the wiring concept. I will also look at where the line connections are made to see if that is consistent with my speculation and a 208V setting. 

Power supply out on bench and partially restored so far

DISCONNECTED MOTORWIRING AND ONE REMAINING WIRE

The wiring to the motor was hooked up on a terminal block on the top compartment of the machine (M Terminal Block), allowing me to disconnect the cable there and pull it down to the lower compartment. There was also a wire coming from a relay RY1 inside connected to another wire that delivers 24VDC to the logic gate. They were soldered together and wrapped with electrical tape, so I had to cut the solder joint to free up the wire. 

Cables and wires removed from machine so PS box can be moved

PS BOX REMOVED FROM THE 2501 READER

I  lifted the PS box out of the lower compartment and transported it on my lift table. I then placed it on the workbench to begin checking out components. 

CHECKED VARIOUS COMPONENTS FOR SHORTS AND PROPER VALUES

I began testing different components that might have failed either by shorting or having their values change so drastically that it could cause damage when power is applied. Among the parts I tested were:

• Diodes used for half-wave rectifiers to produce 24V and 2.5V
• Large capacitors used for filtering as well as ferro-resonant transformer operation
• Transformer winding shorts or opens

As is typical with IBM mainframe produces from the 1960s, the parts were high quality and very rarely fail or drift too much. All the capacitors worked to spec. Nothing was shorted or open. 

CLEANING CONTACTS ON RELAYS AND SWITCHES

What does tend to fail as these systems sit unused for decades are contacts on relays and switches, which form a layer of oxidation which is an insulator. Deoxit spray and work with a burnishing tool returns them to good working order. 

I cleaned the contacts on relays K4 and RY1, using a VOM to verify good conductivity and reliable switching. 

Coil connections in green, one set of contacts used in yellow

Although relay K4 is complex, a 4 pole double throw relay, only a single pole and contact are wired in. 

Relay RY1

USING FUSES TO ISOLATE SECTIONS AS I APPLY 240VAC

The power supply employs five fuses, which I can take out to isolate the sections of the circuits they feed. Fuse F1 controls the 2.5VDC that powers the lamp for the photocell that detects cards in the pre-read station. Fuses F2A and F2B feed the primary of the main transformer which generates the 24VDC, 2.5VDC and 6VAC. Fuses F3A and F3B feed the motor power through a line filter and contactor K1. 

The usage meter power supply does not have a fuse in the circuit, so it is always powered as long as the CE Switch is in the normal position. The fuses interact for certain functionality - the 2.5VDC requires fuses F2A, F2B and F1 to all be working. The motor is fed by F3A and F3B but the contactor K1 is activated by the 24V that comes from the power supply, thus fuses F2A and F2B must be working for the motor to work. 

I have a step up transformer at the bench which I used for convenience rather than hooking the PS box up to 240V directly. This cannot handle the load of the motor but is sufficient to test out power supply sections. 

METER SUPPLY WORKING PROPERLY

I switched the connections for the primary to feed the meter power supply transformer for the 240V present in my shop. I will set it back to 208V when it is ready to ship to the system owner whose facility is powered by 208V. 

I validated that the supply produces 41VAC. It will switch on when appropriate logic signals come from the controller in the 1130 - one wire brings +6V for the relay coil and the other is pulled to ground to activate the relay. This feeds the 41VAC out to the usage meter in the top compartment of the 2501. 

POWER SUPPLY SECTIONS WORKING PROPERLY

. 

xxx

NEED TO WORK OUT WIRING OF TRANSFORMER PRIMARY FOR 230 VS 208

There is a discrepancy in the wiring diagram between the European version and the US version. The schematics I have show four terminals that allow selection of 195, 220 or 235 V mains voltage. Relay RY1 is wired across terminals 1 and 4 in the diagram. 

However, the actual wiring of terminal block PSTB1 doesn't match that and doesn't make sense. There is a metal jumper between terminals 2 and 3. RY1 is wired between terminals 1 and 5 in the US version. Thus I can't make changes to convert this to 240V until I can reconcile the differences. 

The transformer is a ferro-resonant type, which uses a capacitor you can see at the bottom of the picture just above to achieve resonance at the mains line frequency. This saturates the core of the transformer, thus variations in input voltage produce almost no swing in output voltages. This is a form of voltage regulation that IBM often uses. 

Multi-tap transformers for US machines use a different scheme to select voltages, usually involving jumpers as well as moving the input wires to specific terminals. Here is a diagram from another transformer in a US machine that shows how jumpers and wiring changes are used:

As you can see, this doesn't match our terminal block either, since there is a jumper between terminals 2 and 3 on our machine but those would be used to supply the input line voltage per the two diagrams above. I thus have to figure out how the actual wiring I see for PSTB1 would map to 208V and then work out how to change it to select 230V. 

NEXT UP IS WORKING ON MOTOR CONTROL CIRCUITS

The motor control circuits involve several relays and a main contactor K1 to switch the power on to the motor. The motor has start windings that depend on a phase shift relative to the main winding to achieve initial rotation, provided by an RC network that is switched out by relay K2 once the motor achieves speed. 

The 2501 card reader will start up the motor when it needs to read or feed cards, using contactor K1. A timer circuit turns off the motor after approximately 15 seconds, unless another feed or read request arrives to reset the timer. Relay K3 is the time delay relay which sends a signal -Motor Hold back to the controller logic. Relay K4 is activated by the -Execute signal when a new read or feed is requested, and acts to reset the timer for K3. 

 

I will have to clean and verify the contacts on relays K1 and K3, having already cleaned up K4. K2 is a sealed unit providing motor startup functionality and should be safe from oxidation. 

K3 at top, K2 at bottom

Received scan of 2501 card reader logic diagrams and wiring schematics

ASSISTANCE RECEIVED (ONCE AGAIN) FROM A EUROPEAN MUSEUM

A museum that has successfully restored a 2501 as part of an IBM 1130 system did have the diagrams I needed. They kindly scanned them and sent them by email. That is just what I needed to continue with the testing and restoration of the card reader. While the wiring diagrams are for the European versions of the device - 50Hz and 220V - but the differences are fairly minor. The convenience outlet on the 2501 where oscilloscopes or lights could be plugged in are 115V in the US and 220V in Europe, for example. 

INTERESTING DETAILS FROM THE WIRING DIAGRAM

The two main AC legs for 220V are wired directly to the poles of the CE Switch (a DPST switch that disconnects the mains from the rest of the power supply). Thus I only have to remove those two to complete the unhooking of incoming AC to the PS box that I wish to remove and put on the workbench. 

The small relay I saw at the bottom of the PS box, hooked in series with the +24VDC connections out to the logic gate and other machine parts, is used to drop the +24VDC immediately when the 220V mains supply to the transformer primary drops. I assume this blocks any unintended firing of solenoids while the supply capacitor still retains the majority of the 24V. The version of the PS box attached to a 360 model 20 does NOT include this relay. 

Some of the schematics mention a +20V supply, mostly to the different panel switches but also to the hold solenoid that keeps the picker-knives from oscillating unless the other solenoid is activated to overpower it. Since the Field Engineering Theory of Operations manually asserts that the power supply only produces +24VDC, +2.5VDC and 6VAC, I was confused by the mention of this additional voltage level. On close inspection, however, I see that a couple of series resistors drop the +24V down to create the 20V level. 

Disconnecting wiring to remove power supply box from 2501 card reader

WOULD BE VERY INCONVENIENT TO TEST PS WHILE INSTALLED UNDER READER

The power supply and power control box sits in the bottom cabinet of the 2501 card reader, which would require me to lay down to reach inside to properly test it. Making this even more challenging, as of yet I do not have the wiring diagrams and schematics for the 2501; I am hoping I can find someone with a copy that can send me a scanned image. If not, I will need to reverse engineer the wiring to complete my restoration and testing, which will be vastly easier if I can put the box up on the workbench. 

MULTITUDE OF WIRES BETWEEN THE PS BOX AND VARIOUS OTHER PARTS OF 2501

Some wires come to the PS box and are connected to terminals. Others are wires that enter/exit the box and are connected inside. There is the possibility of labeling the wires going onto terminal blocks so they can be reattached correctly. Wires running directly inside the box must either be disconnected inside the box or at the other end where they connect to the reader mechanism or logic gate. 

Two terminal blocks on the outside are the simplest aspect of disconnecting the box for removal. There is a usage meter power box on the side of the main PS box which has three sets of wiring running into it - for AC, control signals and drive power for the usage meter itself. A cable runs up to the AC motor for the drive mechanism. The incoming AC power that arrives on cables from the IBM 1130 system is fed through a cable clamp inside the PS box. 

The IBM 1130 delivers 115VAC, 208/230VAC, and 7.5VAC into the PS box. Other wires in the power cable from the 1130 run directly to the logic gate to feed it +3, -3 and +6V. The PS box itself will produce 24VDC and 2.5VDC for use within the 2501. In addition, the usage meter box has its own power supply to produce the 41VAC to spin the usage meter. 

TERMINAL BLOCKS 2 AND 3 LABELED AND DISCONNECTED

Terminal block 3 delivers the 2.5VDC generated by the PS box up to a distribution box on the top of the reader where it powers the main lamp used to read holes in the punched card as it moves past photocells. Terminal block 2 connects many control circuits inside the PS box to the rest of the machine. 

The 24VDC supply is controlled by a relay inside the box before it is passed along to control the various solenoids for picking and feeding cards. The wires from the relay pop out alongside TB2 and run to the logic gate. 

relay controlling 24VDC

IBM laces their cables very carefully so that the wires for each screw on a terminal block are easy to distinguish as they fall naturally right at the point where they should be connected. 

USAGE METER PS CONNECTIONS UNHOOKED

Two thin yellow wires bring the control signals to the usage meter, driving it to accumulate usage hours when the reader and/or the IBM 1130 are busy. They were connected to a terminal block inside the meter compartment on the side of the PS box. Another pair of wires (red and black) attached to the terminal block runs from the meter box up to the top of the 2501 to connect to the usage meter. 

Lastly, some 208/220VAC wires from the PS box run into the meter compartment and hook to a second terminal block feeding the transformer primary. I unhooked and labeled the logic and usage meter wires, but left the AC connections attached. The meter compartment was unattached from the PS box but will be brought to the workbench along with the PS box. 

AC INPUT WIRING BEING DISCONNECTED

The 115VAC wiring - not, neutral and ground - run directly to a convenience outlet but nowhere else in the machine. I removed the convenience outlet from the PS box and labeled the wires that had been attached to it. 

Plastic box housing convenience outlet

The 208/220VAC consists of two hot wires that are connected within the PS box somewhere behind the four large screw-in fuses. They must also run to the contactor, circuit breaker and cable up to the main reader drive motor. I have yet to find and disconnect these. 

rubber sleeves over terminals on fuse holders

MOTOR POWER WIRING MUST BE DISCONNECTED AS LAST STEP

Until I look more closely, I don't know if this wiring must be removed inside the PS box or up at the motor on the top compartment of the 2501, but it will need to be disconnected before the PS box is fully independent allowing it to be removed from the 2501. 

Motor wiring, 2.5VAC wiring and other signals go up

TERMINAL BLOCK 1 INSIDE PS BOX ROUTES AC TO VARIOUS COMPONENTS

There is a terminal block inside the PS which interconnects various relays, power supplies, transformers, fuses etc. This will require reverse engineering if I can't find a copy of the IBM diagrams and schematics. 

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.