Wednesday, September 9, 2015

Debugging the 1130 button activation by SAC Interface Box enhancement


I had to finish wiring in my changes to the resistor panel deep inside the 1131 to allow my relay board to 'push' the three buttons on the 1130 console, in order to power up and use the system. I anticipated one final 20 minute session on my back inside the frame. In fact, it took a tad less than the allotted time, in part because it is cool this early in the morning.

Relay board wired in place
I powered up the system to verify that the console buttons work as they should, but believe I have some problems with one of my vampire taps. The Reset button works as it should, which is good because my wiring was inserted in series with the switch so loss of continuity would keep the machine in perpetual reset mode.

However, the Prog Start button is not working. Since that is how I will start some code executing, I also couldn't test the Imm Stop button, since I need the machine running in order to verify that it stops. A few minutes after I shut down, I thought of a test I could do that would put the machine into a loop right after it comes out of reset. With my SAC box powered down, interrupt levels 0 and 1 are hot, allowing me to set the interrupt vectors for those instructions to a dummy routine that loops to itself.

I couldn't use the Load mode to set up the interrupt vectors, since this depends on the Prog Start button. I might have been able to load core through the SAC interface box, but it was time to head over to the Computer History Museum for lunch with the 1401 restoration team.

Given the high temperatures today, I wouldn't be able to power up the system for testing until late in the evening. I did a bit of work checking the wiring of the buttons just using a VOM and continuity tests.

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