Tuesday, September 8, 2015

Finished all wiring for SAC Interface Box enhancement, ran console printer diagnostics fully


Testing of the printer had to wait for my SAC Interface box to be able to load core memory correctly with the diagnostic and for the temperatures in my workspace to drop to a reasonable level. It was nowhere near cool enough at 7PM, but I held out a slim hope that it would cool quickly allowing me to test tonight.

I finally gave up, deferring the testing until another day.


I put the VOM on the driver chip and it appeared that the data bit 12 signal was varying, which should have latched it into core properly. I can't find any short or open inside the SAC box, thus I will have to cast my net wider.

I did a continuity test to the pin where the bit 12 signal arrives in the 1131, out to the pin on the driver board in my box. If no continuity was found, I would have a break in the cabling somehow, perhaps at the huge connector for the SAC Interface cable. Fortunately, I did have a good connection and found a teeny wisp that was shorting the signal (I think).

It soared to 98 degrees F, thus I won't apply power to the system until the cooler evening time. Until then power on test, I wouldn't be certain whether the fix works and that I have bit 12 properly being set. In the meantime, I can finish the task of wiring up the SAC enhancement to the 1130 console buttons for Imm Stop, Reset and Prog Start, which I push by program control to simulate a Program Load operation.

I made up a cable after carefully planning the connection means and approach. I put on four pins which fit into the resistor panel underneath and inside the machine, for four wires going up to the relay board. In addition, I have three wires that will be vampire tapped onto the existing wires with pins that fit into the panel.

bundle of wires for button relay, four pins for insertion and three 'vampire taps'
By vampire tapping, I mean I will remove a bit of insulation on the wire up a bit from the pin, wrap my new wire around the conductor, solder, and insulate with heat shrink tubing. As well, I will cover the pins of those tapped wires with heat shrink tubing, since those pins will hang loose, unconnected except by my tapped wires to the relay board.

By the end of my lunch hour, I had the cable made up, the pins installed and it attached to the relay board. Due to heat, I had to take a break before pulling and inserting pins, making vampire taps and securing the heat shrink tubing with a hot air gun.

A task like pulling and installing pins would be dead easy if the panel were directly in front of me, not wedged up in a dark corner of the 1130 frame with blocked visibility and access. I have to contort on the floor, with my body partially inside the frame, just to make the attempt. Also, the wire covering on the existing wires is quite strong and not easily stripped loose for the vampire tap.

I managed to pull the first two pins for vampire taps, those for the Prog Start button, melted access and soldered on the tap to the first of them, before the heat got to be too much. At this rate, it will take about four more 20 minutes bursts of contortion and baking before I finish up the wiring task at the resistor panel. Nice long breaks to cool down in between, of course.

The time estimates are holding up - second 20 minute interval spent, two soldered vampire taps, two pins inserted, another tap and two more pins to go plus the insulation. In my third 20 minute roasting, at 6:45PM, with the conditions still 92F outdoors and 88F in the workshop, I got more done. Remaining for the last time in the over is insertion of one new pin, the last vampire tap, plus insulation of everything with heat shrink tubing and the dreaded heat gun. . 

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