Monday, February 16, 2015

Worked on shed, 1442 card reader, DMS card decks and SAC Interface debugging


I began reassembling the feed clutch in the reader today. Things went smoothly until I hit two snags. First snag - the taper pin to hold the index wheel on the shaft didn't go in far enough, in my opinion, but it won't budge. Might need to drive it out and try a different way. Second snag - can't maneuver the pushrod behind the read clutch that connects the clutch actuator and the read mechanism above.

There isn't enough clearance to hold the pushrod in place. The read clutch lever can be moved by hand to open the gap and then close over the end of the rod, but I have to stand it in a ball socket at the bottom and pull the top of the pushrod under the clutch lever. The pushrod sits behind a metal casting, blocked by various mechanisms from any direct approach.

I can stretch fingers round from behind to touch the rod, but not much more. I don't have the dexterity to hold the rod and move the bottom end into a socket that I can't see because my hand blocks the view. Further, even if I get that end placed in the socket, I can't swing the top end to fit under the read clutch. A magician might have the extreme dexterity, or a much younger person, but I don't. I can't find an angle where any tools such as forceps can help me with this task.

Light was failing as the evening approached, a good time to pack up the reader parts and manuals. Once I am back from my business trip to Texas this week, I can resume putting the reader together.


I discussed the tape with Lyle, who has the equipment needed to convert the files, if readable, into transportable files I can pass back to Clare who loaned me the tape. If any of the files are general interest software and not just examples of client programs he wrote.

Lyle lives near me, making it easy to drop off the tape or have him stop by to pick it up when I am back from the trip.


After collecting all the binary phases from the DMS V2 R12 deck, I found that there were 72 missing phases, not just COBOL and RPG but also parts of the basic system. I will have to wait until I can extract the remaining files from disk onto either physical cards or directly to a PC file. has source code listings, recreated from Microfiche and interpolation, but I will keep working until I can build the canonical distribution files.


I put my new digital storage oscilloscope on the SAC receiver circuits and monitored two signals. The basic oscillator of the 1130 and then the T6 time signal. The voltage levels looked good, but there was an unacceptable delay in the timing of the output pulse. T6 rises for a bit over 300ns at a time, but the output of my receiver circuit didn't start rising for about 200ns, dropping rapidly after the incoming pulse had dropped - not even giving me a delayed 300+ ns signal but instead something on the order of 100ns straddling the end of the incoming pulse.

Further, none of the lights wired to the FPGA display signals, they are all dark regardless of the slide switch positions on the fpga board. Further, the push buttons that should trigger interrupt levels yield no result on the 1130 or lights on the fpga expansion board. It looks like the fpga is not working and perhaps whatever is wrong with it is delaying the rise of the received signal.

I hope the fpga board didn't die - I bought it just before the maker stopped selling them, thus a replacement will be very hard to find. I will have to change the FPGA hardware to blink some lights as a startup sequence.


Out to the shed in the morning to continue with the wiring process. Observant readers may have noticed that the heading on yesterday's entry was excessively optimistic, claiming completion of the wiring task. I didn't anticipate the pace at which I would crawl through the work.

I used UF (underground feeder - weatherproof cable), 8 ga which is huge, double the capacity needed for the machine but I selected it to minimize voltage drop. It is very heavy and harder to work with, making each connection and trimming a slow process.

When I wrapped it up, all that was left was to receive my 240V double pole 20A breaker, install it and close up the load center, plus some lighting work. I have the light wired up through the on/off switch but until I finish building the top lights I will use, I can't hook them into the top terminal box.  Otherwise, the inside of the shed is complete. I have a bit of silicone sealing to do on the outdoor enclosure box then it is ready once the circuit is hooked into the main circuit breaker panel.

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