week ending Oct 27, 2013 - progress report

CONSOLE TYPEWRITER DEBUGGING AND CONSTRUCTION

After battling my way through the failure of the automatic new line function, where the logic hung up after the return, I finally got to the root of the problem. Ugh. When I switched from the Electronic 50 typewriter to the Memory typewriter mechanism, I reused the input-output pins of the fpga for the new signals. I carefully changed them to the new signal names, but forgot to look closely at some parameters I had on there.

Specifically, some of the switches and sensors on the ET50 needed the port to be set with a pullup resistor, so that it floated to level 1 unless the switch was grounded. The Memory 50 interface,on the other hand, is driven by its logic board and will drive to either 1 or 0 by itself. Leaving the pullup activated kept the fpga from getting a reliable switch to 0 when the solenoids fired, because the pullup interacted with my incoming signal. The result was that my logic was not seeing many of the solenoids I believed I was watching. Since the carrier return and escapement solenoids were two that had this flaw, they were never detected.

That was why my adapter didn't work correctly. Once I saw the problem and removed the pullup directive, the automatic new line worked flawlessly. When I set the IBM diagnostics to continually type letters, it would type until the right margin, return automatically and continue typing from where it left off, all without a hitch.

Days wasted, but in the end it is working quite well. The testing of the tab set, tab clear, right margin setting and typewriter command buttons began Monday night. Setting the right margin was easy to test - I spaced over about half the normal distance, pressed the button to set the margin, then did a return. When I ran the
diagnostics to type away, the automatic new line occured exactly as expected.

The only challenge I see is that once the margin is set to some point, it is not possible to space or type beyond that point to set the new longer margin. I will have to add a circuit to block the recognition of the bell, for when I need a 'margin release' for the right margin, perhaps tied to the physical margin release I will have rigged up to release the left margin.

I added some logic to run at startup time to force the typewriter to the lower case state and put it at the left margin, to sync with the expectations of the 1130 typewriter adapter logic. I am still testing this, as initially I didn't fire the strobe to activate the two requests. The tab set and tab clear aren't working, which I suspect is a matter of timing. I am only 'holding down' the button for 10 milliseconds, which the logic board might be blocking with it debouncing. I have increased the pushdown time to almost half a second, which should be enough.

The final test of the typewriter interface and my adapter logic exercised the set right margin , tab set, and tab clear buttons plus the typewriter mounted space, return and backspace buttons, then finally the correct startup time behavior. The test showed the adapter logic is working as intended and reliably. Nothing more has to be done to the adapter logic. I ran the IBM written typewriter diagnostics first and worked it at maximum speed to verify all functions. I then executed a short 1130 program I hand coded and entered into the system - it exercised the programmatic interface for starting IO, handling status and interrupts while it wrote some text to the console printer at maximum speed. Once again, this worked perfectly.

Quick video of a program running in the 1130 writing a short message to the console printer Video demonstration

Printer mechanism during video recording of a test

What remains are hardware tasks - making a modification to the typewriter so that it uses a single uniform strike velocity for all characters, building a 1053 style housing and mounting it on the 1130 system frame. As well, the escapement mechanism is slightly out of adjustment, showing up on the tab test of the diagnostics and once in a while when printing many lines of identical text where slight misalignment is most visible, so I will fix this up.

I have designed a modification to convert the mechanism to monovelocity rather than the built-in low and high velocity force assigned to characters. These assignments are based on typewriter (correspondence) format typeballs but are inappropriate to use with my 1130 layout typeball. My circuit will fire both the low-velocity and no-print solenoids whenever the logic board attempts to fire the no-print solenoid line, while I ignore the line activating the low-velocity solenoid.

The typewriter activates the low-velocity solenoid by itself to print with low velocity, but activate BOTH low and no-print solenoids to block printing. Any time the no-print solenoid line is activated by the logic board, it means it is also activating the low-velocity line, but the low-velocity is sometimes activated by itself for characters it wants to strike lightly. I fire both anytime the no-print line comes on, which implements a non-printing cycle, but unhook the low velocity signal wire from the logic board. My circuit drives both solenoids from the single logic line activation.This will disable the dual-velocity feature, giving me the monovelocity behavior of the 1053 printer used on the 1130 system.

I have breadboarded the circuit, am adjusting component values to fine-tune its operation at this time, then will build a mini-board with the circuit and hook it into the typewriter mechanism for testing. The completed miniboard is ready for testing next week.

Minicircuit to disable low velocity mode on typewriter mechanism

I have a temporary frame on the typewriter allowing it to be free standing while I measure and plan the enclosure to turn it into a visual replica of a 1053 printer.

TYPEWRITER POWER SUPPLY REPAIR FOR A FRIEND

The replacement transistor arrived on Wednesday, I soldered it into place and the power supply is now working perfectly. Both are repaired and ready to mail back to my friend Lukas in Switzerland. Very happy I could help him out like this and without taking much time at all.

I repacking them in a sturdy box with solid padding and mailed it back to him on Thursday. Should arrive in a bit more than a week.

INSTALLING 1401 MAINFRAMES AT CHM

This week, the two 1401 systems and their peripherals were ready to be installed in their new facility where visitors to the museum will view them in operation. I helped line them up, plan the floor openings and worked out details in the tight and irregularly shaped space in which it will go. By the end of Saturday, we had all the power and signal cables hooked up for both machines, and succeeded getting the CT - "Connecticut" -machine running with everything except the tape drives which will be hooked up later in the week.

Beginning to open floor tiles and install cables

                                                       Photos of install work taken by Ed Thelan

The other 1401 system, DE or "German", wouldn't power up when we attempted it. It appeared that we had a problem with the power being delivered to the system. The DE system came from Germany which means it was set up for 50Hz power. The museum has a full rack of power equipment that converts building electricity to 50Hz 220V three phase in order to drive the DE system's units, which makes this a bit more complicated than the other system.

The only changes that occurred were moving the machinery and electricians wiring them in place. Likely there is something off in how the main power feed is wired, as the 1402 box that receives it won't complete its power up sequence. The team will be looking at the power more closely on Monday.

Swapping phases of input power on CT system

It was great to see the CT system power right up, pass diagnostics and run some simple programs to list card decks on the 1403 printer. The work of cabling these was physically demanding. The cables are thick and plastic sheathed, between one and two inches in diameter and up to thirty feet long. They have large connectors on the end as well or printed circuit cards hanging off individual wires coming out of the cable end.  They had to be placed under the raised floor tiles in the room. Tiles had to be lifted out of the floor, the cables threaded along around the metal 'feet' that hold the the floor, power and water pipes, and the scattered sprinkler heads that would have flooded the room if we had banged into one.

Me diving under floor to push cable to Frank King. See some cables snaking down at right

Our boxes were closer together than the cable lengths, which meant we had to figure out a big looping path that would keep them out of the way of airflow or other cables, avoid sharp bends in the cable, all while bringing the connectors on the end up through holes in the floor tiles at just the right height and location to fit into each box. Several of the cables were run under the part of the raised floor where visitors will walk, as it would have no need for cooling airflow, others had to be placed under the parts of the floor which were the gaps between boxes.

The museum will open the facility to the public on the 20th of November, which gives us less than a month to get everything up and running properly, then train all the presenters and operators who will conduct the demonstrations. The work this weekend puts us well ahead of schedule, versus the requirement that we have the CT system cabled but not yet powered up and that the DE system might not have been touched at all.