ONE OBSERVED ISSUE - ONE LAMP DID NOT LIGHT
Lamp Test failed for the Accumulator Extension Register bit 10 position. It was not the bulb, thus I needed to inspect this further and repair whatever is wrong. It wouldn't light with either the Lamp Test activated nor with a +3V signal on the input pin.
That suggested that my problem was likely another bad solder joint. Having selected 2 ounce copper pour for my PCB, I had to deal with the higher thermal mass of the pads. It took a longer time applying heat for the pad to flow solder, while the gate lead of the thyristor would flow much earlier. I ended up with a couple of heaps on the component lead that didn't attach to the pad underneath.
Reflowing the joint fixed the problem immediately. I verified that both the signal input pin and the Lamp Test control would cause it to light.
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