Finalizing work on SSM 1053 console typewriter

SYSTEM SOURCE MUSEUM CONSOLE PRINTER BROKE A ROTATE TAPE

During the VCF East event, the rotate tape of the console printer on the recently restored System Source Museum 1130 broke , while it was being exhibited there. I brought just the typewriter back with me in order to change the tape and make sure it was in perfect condition before returning to Baltimore.

FINE TUNED ADJUSTMENT FOR ROTATE TIMING

With the new tape in place, I carefully examined and tweaked the timing of the machine to ensure that the tapes are not subjected to any extra stress. During a print cycle, the mechanism first pivots levers to pull or release pressure on the rotate and tilt tapes, positioning the typewriter ball at the proper character. Next, the mechanism pivots locking (detent) bars to lock the type ball in its exact position before it strikes the paper. The ball is flung forward to strike the paper.

After hitting the paper the locking bars get released so that the rotate and tilt tapes can return to their idle positions; meanwhile, the type ball continues its returns to wait for the next print cycle. The timing of the locking bars and the rotate/tilt tape movement have to be synchronized. If the tapes change pressure while the ball is locked, it adds stress to the tapes; if the tapes have not finished moving yet, the ball can be locked on the wrong character in addition to putting strain on the tapes. 

A print cycle involves a 180 degree rotation of the cam shaft,  driven by the main motor when released by the print clutch. This cam shaft directly turns cams that pull down levers to select and drive two metal tapes. Those tapes move on a pulley system and run to the print carrier where they tilt and rotate the ball. The motor is continually turning the right side of the shaft, called the operational shaft, but the clutch keeps the left side, the cam shaft, from turning except when the clutch engages for one cycle. 

The cam shaft is also connected via a gear train to a print shaft that the print carrier slides along. This print shaft has a slot along its length that turns mechanisms in the carrier. The rotation of the print shaft inside the carrier moves the type element forward to print a character, but also engages the detent lock to hold the ball in position for the strike and does other actions such as advance the ribbon. 

The relative timing of these two shafts is adjusted by loosening setscrews in the gear on the end of the print shaft, then moving the print shaft to the point it needs to be relative to the position of the cam shaft. Any movement of the pivot levers that are rotating and/or tilting the type ball must have ceased before the detent is engaged. This holds the ball until after it has struck the ribbon to impress a character on the paper. 

The detent should be released before the pivot levers start to return to their idle conditions, turning and tilting the ball to its home position. The time when the detent is engaged must be aligned very well with the print selection done by the cam shaft which is ultimately swinging the rotate and tilt pivot arms. 

I hand cycled printing while adjusting the timing of the locking bar and print ball movements. I wanted the locking to start AFTER the ball reached its final position and to be released BEFORE the tapes start releasing. If that works properly then the tapes will last a long time. 

I had found that the IBM documented procedure for setting the relative timing did not directly look at the detent lever movements nor the pivot arm movements, instead dealing with secondary indications that I believe are less reliable in achieving the correct operation. 

I will try a few under power later, perhaps, filming in slow motion, but as far as I can tell with very careful hand cycling, the timing of the detent lever latching and the rotate and tilt tape movements are perfectly synchronized. 

NEW ACRYLIC LID FOR PRINTER BEING BUILT

I designed a thick lid for the 1053 typewriter cover as the SSM machine did not have its original IBM part. I will have to glue a couple of small blocks to the underside that will engage the springy metal on the cover that holds the lid in place. This is not an exact copy of the IBM lid, since that has curves and bent sections that would be very challenging to duplicate, but it provides the same function and will look very similar to the casual observer. 

POWER CONNECTION SMS PADDLE CARD REPAIRED

During the removal of the typewriter at VCF, I noticed that the SMS paddle card which connects the 1053 to the power block of the 1130 system had sustained a crack. This broke the metal traces between the card fingers and the spot where the wires were soldered down. 

After an epoxy repair of the card itself, I added some bridge wires to restore connectivity across the line of the crack. The card delivers 115VAC for the motor, +48V for the solenoids, the system ground connection and frame ground that protects users touching the case. Thus the card can now be plugged in and used successfully. 

REINSTALLATION INSTRUCTIONS TO BE PREPARED

I am typing up some instructions for reinstalling the console printer onto the 1130 system. The main difficulties surround the insertion of the cables into the 1130 since the SMS connectors for power and signal lines are buried down inside the machine and can be confusing to a skilled technician who is not totally familiar with IBM systems of that era. I will use lots of pictures to make it easier for the staff that has to put this back on their machine. 

Restoration work to resume and ramp up over the coming weeks

HAVE BEEN HELPING MY WIFE AFTER HER MAJOR SURGERY TWO WEEKS AGO

Due to the surgery on her lower spine, she can't bend or twist or lift for a number of weeks until the bone in her spine fuses around the titanium hardware. Further, until yesterday she had to take pain and related medications as she healed. I therefore had to be home to care for her and handle all the tasks she was unable to accomplish.

We are reaching a point where I can be away for intervals of a few hours, although our dog Kerry needs regular walks which requires me home even if my wife Nancy is otherwise okay. Still, I expect that I can get in about one day of work this next week and increase gradually after that, thus I can get back to the restoration tasks. 

DMA based memory loader circuit boards have arrived

 PCB SHIELD FOR ARDUINO

I have received the circuit board that will plug on the top of an Arduino Mega 2560 and implement the function. I will solder on the chips and other parts soon so that once the 1130 is working sufficiently well to do memory cycles and cycle steal, I can test out my design.

HEADERS TO ISOLATE WIREWRAP FROM THE LOADER BOARD

I wanted the wires that will be linked to specific backplane (in IBM-speak, the board) pins to interface my loader to the 1130s logic. The header goes above the board at the top of the gate and I will use wirewrap to make connections between header and board pins. 

Cables will connect the headers to the shield PCB on the Arduino. 

Power sequencing problem found and repaired

TRACING DOWN THE FAULT IN THE POWER UP SEQUENCE

Sometimes you can test each section of a machine and find no problems, because the defect is in the interconnection. I had extensively tested the SMS sequencing card and also reverified the wiring to the SMS socket. I could observe the three primary supply rails were present at the correct voltage at the pins of the socket as well. 

Thus, it should have worked but it didn't. As I did more and more involved tests, probing parts on the board while it was in operation, I heard the relays click on and off as I applied pressure to the test point. This was the clue that led me to determine that the corrosion on the contacts of the SMS connector were introducing high resistance or causing intermittent connections. 

FIXING THE PROBLEM

Applying deoxidizing solution to the contacts and wiping them by inserting the SMS card cleaned up the contacts. The power sequencer now brings up the machine properly, delivering +12V and +48V to the machine because the main rails are working correctly. 

MACHINE NOW UP WITH LAMPS AND BUTTONS ACTIVE

When +12V is delivered to the logic gates, we will see the indicator lamps and pushbuttons that surround the keyboard on the console function as they should. The Prog Start and other buttons can be pressed and result in appropriate actions based on the rotary mode switch setting. For example, each time the machine takes a step or executes instructions, the Ready lamp will glow until the processor enters a wait state again. 

Indeed, the machine came up with a few lamps glowing. File Ready and Parity lamps were illuminated. The first is understandable since I have the drive out of the machine so that the controller logic is interpreting its state incorrectly. However, the Parity error is an issue I have to troubleshoot.

FIRST TESTS OF FUNCTIONALITY

The lamp test switch does not illuminate all the bulbs in the display pedestal as it should. The Storage Display and Storage Load switches won't cycle through memory even with the Parity Run switch set which does not set the stop latch on errors. Pushing Prog Start button does not flick the Run lamp on, although that may be a consequence of the parity error. 

Given the corrosion I detected with the power sequence connector, it is likely that I have to deoxidize all the switches before they will work correctly. I most likely have a memory related issue as well. I like to work carefully from the most central points of the machine outward, so I will begin some testing to determine how healthy the logic may be and the areas that are failing. 

Tested regulator under load; working on power sequencing issue

OUTLET INSTALLED IN WORKSHOP

The workshop had its 230V receptacle installed today, something that was necessary to continue restoration work on the VCF 1130 system's power system. I had wanted a 30A receptacle with four wires (ground, neutral and hot lines from different phases), so that I could pull 115 or 230 depending on the wiring of the plug I insert. 

What I had mentioned earlier to the landlord was an L6-30 receptacle, which is three wire, lacking the neutral. This is a 30A 230V only outlet. That is actually fine for the work I am doing now, so I was able to proceed with my testing. 

L6-30R outlet

REGULATOR UNDER 15A LOAD FOR FINAL TEST

Now that the 230V outlet is installed in my new workshop, I could power up the VCF 1130 system to test the +3V regulator. The resistor network is installed which will draw 15A at the nominal 3V output of the regulator. It could be split to start out at 6A draw, 9A or all 15A. 

The expectation is that the voltage setting under the various load levels will be essentially the same as with no load. This ensures that the regulator is working properly. 

I powered up the 1130, with only the +3V regulator switched on. Pin A of the SMS card that sequences power was disconnected - this pin is used to shut down the machine if all three primary voltages (+3, -3 and +6) are not present within a few seconds of power-up. Since I will only be working with +3, I had to pull this wire to leave the system switched on. 

The voltage with no load was set to 3.01V and then I connected the resistors set up for a 6A load. The voltage was still 3.01V at that current which was exactly at the starting point. 

Resistors producing 0.5 ohms for 6A draw

Regulator maintains voltage at 3.01V

I changed the wiring of the resistors to draw 9A and saw 3.01V measured. Once again, holding the voltage very accurately.

Three groups of resistors for 0.33 ohms, 9A draw

Still holding at 3.01V

Finally, with the resistors wired to load the regulator to 15A, I saw the output voltage sit at 3.01Vfor at least a minute. I can declare the power supply completely repaired and working as it should. 

Resistors set for 0.2 ohms, 15A of draw

Holding exactly 3.01V

Next up I connected the logic to the voltage regulator outputs, put pin A back on the sequencing card, and then brought up the system to adjust the voltages as seen at the base of the logic gates. The specifications are:

    -3 supply      between -2.88V and -3.12V
    +6 supply     between +5.76V and +6.24V
    +3 supply     between +2.88V and +3.12V

I set the voltages to 3.01V, -3.01V and 6.01V but did notice that the machine would drop power and lock out the power switch after five seconds even though all three regulators were online and putting out the correct voltage. 

ISSUE TO DEBUG IN THE POWER SEQUENCING LOGIC

The 1130 feeds the output of the three main power regulators to three relays on an SMS card. Then the three relays are all energized, the series circuit is completed to power on relay R1 in the main power sequence box. The purpose of R1 is to switch the +12V and +48V supplies into the logic circuitry. 

However, R1 has a second purpose. If R1 is not activated by the time the 5 second time delay at power-up has finished, then pin A of the card will latch in another relay which drops power to the machine while remaining energized to remember that there was a power rail issue. The main power switch does nothing while this new relay is energized. The CE has to flip a switch or remove building power in order to reset the relay and allow another power-up attempt. 

Power validation circuit to ensure +3, -3 and +6 are present

I had verified that all the voltage rails are present and at the proper levels, but the card is no activating R1. I did a quick test of the voltage on the card pins K, M and N relative to pin C which should show the +6, -3 and +3 levels respectively. The -3 pin was reading only -1.9V but the main regulator was continuing to produce -3.01V as it had been set. 

I did some testing of the SMS card to verify that the parts are okay. Using bench power supplies I confirmed that the three relays RR2, RR3 and RR4 would latch as their respective supplies were connected. Further, I verified that the series circuit worked through the relays which should have triggered relay R1. 

SMS card with RR1, RR2, RR3 and RR4

I had to leave the workshop before I could delve further into the issue. However, since we do have good power, resolving this should be easy. While I could pull pin A off the card so that it didn't drop machine power, without relay R1 being activated we don't get the +12V and +48V supplied to the logic. Since the mode switches and pushbuttons are powered by +12V, the machine can't really be debugged until I get this section fixed. 

I did see a good state reflected on the display panel, indicating that the machine was set up properly by the power on reset and was apparently ready to do more once it had +12V active. 

Validated design for 1130 core loader (DMA version) sent to fab after testing session

BREADBOARD TESTED NEW DESIGN

I changed the breadboard to the new design I created for the DMA loader circuitry and put it through its paces. Initially I had a problem with switch bounce but a debouncing pushbutton on my Cadet did away with that issue so that I could test with confidence. 

I expanded the test setup to show the state of the control outputs I generate as the state machine operates, to be certain they were correct. I drive both -CS Level 0 Request and -File Data Entry Gate low with open collector chips - temporarily added pull up resistors to be able to see the outputs. I also drive the enable line for the Address and Data words; when a bit of an address or data word is 1, it will pull the output low but only when enabled. 

PCB DESIGN SENT TO JLCPCB

I packaged up the Gerber files and drill information in a zip file and uploaded it to the fab. I chose a blue color for the solder mask with white silkscreen images. It will take 3-4 business days to complete manufacturing, then 3-5 days for shipping. The components are all waiting at the shop for the boards. 

Slowly digging through boxes and setting up the shop; testing the DMA loader logic uncovered an issue

SETTING UP THE SHOP

As this is a new space, I am not certain of the best arrangement of equipment, tables and the many boxes of components I have. Further, the boxes were all taped shut and are piled in random order in large heaps. I am still pulling tape off boxes, although probably eighty percent have been done by now. 

With the heaps piled along the walls, each time I decide to place a table I first have to drag boxes and equipment away from that area to make room. I have five of over twenty tables in place, at least to a temporary location. Then when all the boxes and other items are moved and the tables are placed, I have quite a few boxes which are either unsorted or that need further division into smaller boxes to make searching easier. 

BREADBOARD TEST RUN ON THE MAIN SEQUENCING LOGIC OF THE LOADER

I used my Cadet breadboard to set up eight of the chips from the design, ignoring all the output buffer chips for the time being because once the enable signals are emitted at the right times, they are certain to work correctly. 

I found that my scheme to reset at the end of a cycle was timing sensitive and potentially glitchy. I revamped the circuit, which had the side effect of cutting two chips from the design. All the online logic simulations show it to be solid, but I will go back to the breadboard and make sure it is rock solid before committing the updated layout to the PCB plant. 

BUSY DAY AT THE CAPE TOMORROW - NO TIME FOR THE SHOP

I am supporting two launches tomorrow - a SpaceX Falcon 9 launching Starlink satellites, and a ULA Atlas launching the Boeing Starliner capsule with two astronauts. I am helping secure one viewing location. In between, the monthly SF Museum volunteer meeting will take place. Basically I will be onsite the entire day and evening. 

Quick update; regulator is indeed working properly

HAD A SUSPICION THAT MY TEST SETUP WAS AT FAULT

One of the possibilities to explain the voltage dip when I went up from 1A to 4A was that my test setup was not a sufficiently accurate replacement for the attachment to the raw DC supply in the 1130. If so, the regulator might have maintained its voltage while connected in the 1130 although it wasn't doing that on the bench. 

The first thought I had was that the AC bias voltage somehow compensated for load differences, so I varied the bias supply but saw zero change in the delivered voltage. Just before I broke down the setup because I believed the 086 transistor replacement (2N214) was unable to drive enough current due to its lower beta, I had another idea.

Putting the multimeter on the output terminals themselves, rather than depending on my electronic load to display the voltage, I was surprised and pleased to see that the voltage coming from the regulator itself was precisely the same voltage at 1A, 4A and no load at all. Clearly, the voltage drop was occurring on the cables between the regulator and my electronic load, due to the resistance of the cable. 

This is great news, as it means that I have only one test left, the full load test while bolted into the machine. I placed the regulator in the machine again. My resistor network produces a resistance of 0.2 ohms and can handle 200W across all the resistors that comprise it. For the +3V regulator, that means we will draw 15A from the supply. If the voltage stays essentially flat under this load, then the regulator is completely repaired and ready to go. 

0.2 ohm load for testing

Load connected to the supply

I just need to wait until I get my 230V outlet installed to bring up the 1130 and begin some functional testing. 

Progress on voltage regulator for VCF 1130; made plexiglass cover for SSM console printer

QUICK SCHEMATIC DRAWING ATTEMPTED FOR EBAY VOLTAGE REGULATOR CARD

SMS cards are very easy to reverse engineer, because all the components are discrete and visible. More importantly, the PCB has traces only on one side, with wire jumpers soldered when signals have to move across the component side. The parts are all labeled so that I can tell their value with the exception of three diodes - two Zener and one normal diode (that rectifies the AC bias input). Given the similarity to the previous SMS card, I expect the Zener diode values to be identical in the new card. 

I began beeping out the connections from the SMS card fingers to determine where the circuit would diverge from the previous card to this one. During this process I got a beep where I shouldn't. The card has a large 108 PNP transistor on a heatsink that is the final stage which drives current through the output transistors. The emitter and collector had almost zero resistance - shorted out. This is not true with the other card (or any properly functioning 108 transistor). 

Therefore this is not functional and can't be inserted into the power supply as a substitute. It reverts to its original status as the parts donor. 

DEALING WITH THE 026 TRANSISTORS ON THE ORIGINAL CARD

I desoldered the two 026 transistors that form the comparator on the regulator card, so that I could test them on the curve tracer. I found that there was a 3X difference in beta (gain) between the two transistors. Without a spec sheet or a known industry alternative part number, I couldn't determine which was bad at this point.

I then removed one of the 026 transistors from the ebay card and put it on the curve tracer. I now had two 026 with identical gains and curves, plus a third that was much higher in gain. It seems quite reasonable that the two transistors in a comparator should be as equal as possible, so I put the similar pair back on the card. 

INSERTED CARD IN REGULATOR AND TESTED AT LOW LOAD

With the card now possibly repaired, I plugged it into the regulator and set up the power supplies and electronic load. The regulator is fed 8-9 volts DC from one supply, which in the machine comes from the unregulated raw DC supply. The machine also provides 8-9V AC to the regulator which is turned into a DC bias voltage by a half wave rectification on the SMS card. I used another power supply to provide a DC voltage in lieu of the 1130's AC input. 

My electronic load was set to 1A, enough to be able to assess whether the machine is holding a fixed voltage. I then adjusted the potentiometer on the card to set the output voltage at just over 3V DC. 

This did the trick. The regulator kept the same voltage for long periods of time, unlike its prior behavior where it began to run away after a few dozen seconds. I bumped up the load to 1.5A, 2A and 4A to see how steady the output voltage remained.

I was not completely happy with the outcome. The regulator sat at 3.04V while at 1A, but declined a bit with each bump in current until it was at 2.96V at 4A. This could be one of two things. First, it could be an artifact of how I am powering the supply on the workbench. Second, it could be due to the lower beta of the transistor I used to replace the 086 on the card. 

In the real machine, the bias AC supplied to the regulator comes from the winding of the raw DC supply that feeds the regulated supply. This might change under load and somehow compensate while my bench setup feeds a fixed DC voltage to the regulator. If this is the case, then the regulator card is really working properly and I can consider this fully repaired.

On the other hand, the lower beta of the replacement transistor might not produce as much drive current, therefore the regulator might not adjust as much as it should as the load increases. The solution to this would be to find a better replacement or even try the original 086 back in the card. 

REGULATOR INSTALLED IN VCF MACHINE

I bolted the regulator back into the machine and installed some of the wires to it. I can do load testing first with my electronic load up to 5A and then with my resistor networks for a much larger load. That will determine whether the regulator is actually working good enough or if I have to keep working on a substitute for the 086. 

HIGH LOAD TEST WILL CONFIRM PROPER OPERATION OF REGULATOR

I used my network of power resistors to load up the regulator to 16A, which is higher than the draw from the 1130 it will be used in. The aim is to see if the voltage remains nearly constant when under load, which proves that all four of the power transistors in the final stage are working properly.

The next stage of testing, when all the power supplies are working correctly, is to adjust the voltages to the target levels for the machine by reference to the terminal blocks attached the logic gates where the DC is delivered. I need the 230V outlet in my workshop to power up the machine, but the owner of the unit is waiting on the electrician to arrive to install the outlet. 

DESIGNED AND HAD PLEXI COVER BUILT FOR SSM 1053 PRINTER

The 1053 console printer for the System Source Museum 1130 system did not have the plastic cover that fits in the lid. This protects the printer from objects falling in as well as reducing the sound produced as it types. The IBM part is a complex shape which was unrealistic to copy but I had a flat piece laser cut from plexiglass as a substitute.

The plastic IBM part has notches on the underside where springy metal wires hold it in place and against the front of the lid. I cut some small bits of acrylic to provide the same notch and glued them to the bottom of the cover I just had made. It fits well and looks appropriate. 

Cover without notched pieces added

DMA Core Loader PCB has issues - gambled and lost; intrigued by 360 voltage regulator card I bought

DISCOVERED A FEW ISSUES WITH THE PCB DESIGN ALREADY

I have not completed all the testing yet with breadboards and an 1130 but I have already discovered a couple of flaws. One of the issues would be a huge pain to resolve by cutting traces and adding bodge wires, so I won't bother. I knew the risk when I submitted the first design; just a few dollars wasted. 

I did take the time to optimize placement of the decoupling capacitors, which generally involved relocating quite a few unrelated traces to make room for the capacitor as close as possible to the chips they support. 

I have a new PCB design set up in KiCAD but will hold off sending it to be fabricated until all my testing is done. This adds some schedule delay waiting for the boards after the testing wraps up, but it minimizes the chance that the next set of boards requires any rework. 

EBAY PURCHASE OF 360 REGULATOR CARD MAY BE WORKABLE REPLACEMENT

I purchased a card on Ebay that had the 026 transistors I lacked to repair the VCF 1130, thinking that it was incompatible but a good parts source. The documentation I have for the 1130 shows two versions of the voltage regulator, a 'previous' and a 'new' version. The VCF machine has the previous style. The new style is different enough that the regulator card and the supply can't be mixed with pieces from the previous type.

However, examining the new card shows that it is neither the previous nor the new type. It is however pin compatible with the previous style and may work just fine with the supply. This appears to be a newer design leveraging a later IBM transistor than was available when the previous card was designed.

The previous type used an SMS card that had twin 026 transistors as a comparator, an 086 driving an 028 which then drives the final 108 transistor on the card. The 086 is NPN while all the other transistors are PNP. 

The new type SMS card has twin 026, but they are amplified by a chain of two 183 transistors before driving the 108. One of the 183 has a heat sink pushed on it, thus it is the second stage of amplification. I don't have schematics for the card but will produce one by some reverse engineering. The design appears similar enough to the previous SMS card, other than the change to deploy twin 183, that I suspect I will find the circuitry pretty similar outside of the areas directly driving the 183 parts. 

Previous on left, mystery board on right

The workshop is moved! Faster than I thought and a bit more casual

SCRAMBLE TO MOVE TODAY INSTEAD OF TOMORROW

The Chiropractor who is expanding into the storefront that was my current workshop had promised to move everything and had detailed specs from me on the dimensions and weights of all the larger equipment. We had arranged for his movers to come tomorrow to move the heavy items, but yesterday afternoon he called to try to do the move today.

He said the movers only had today available out of the entire month so it had to be today. I on the other hand had two important appointments that could not be moved and I was not going to have people move the items without being there to supervise. Since I could be back by 1PM after the last of my appointments, we settled on that time for the move. 

I envisioned a larger truck, lift gates or fork lifts, thus was surprised to see a trailer on the Chiropractor's pickup truck suitable for hauling a riding lawn mower. He had several friends, his wife and his new partner in the practice to accomplish the move. 

What made this feasible was that my new workshop was only a block or so away thus a very slow careful drive was possible and short travel time supported multiple round trips. We began at 1PM and by 4:30PM every last item from my shop was in the new space!

Everything is there, but I have to figure out how to organize the space and locate everything. That may take some time, but I can fairly rapidly return to working on the VCF 1130's voltage regulator, the SSM 1130's typewriter and the VCF 1130's disk drive. Too, I can test my design for the DMA based core memory loader. 

Ordered components for DMA based core loader; arrived home today

COMPONENT ORDER PLACED

I sent the final order for the ICs, voltage regulators and terminal block to Digikey, so that I should have both PCBs and parts on hand by the time I am set up to do the assembly. The design has eighteen chips, all surface mount parts, which fit on the PCB. 

HOME FROM RHODE ISLAND TRIP TODAY

I landed this morning and am headed over to complete the final packing, labeling and arranging of everything in advance of the move which will begin on May 3rd. With the move itself seeming to be well in hand, I am starting to look ahead to the challenge of working out a layout for all the tables, boxes and machinery in the new location. Once that is done I will need to sort and place the containers then deal with all the partially or fully unsorted last minute containers I had to fill. 

I will be able to set up the bench fairly quickly for work on the 1130 voltage regulator as well as the assembly table to build the DMA loader. Thus I will be able to accomplish productive work interspersed with all the housekeeping activities.