Re: That 'scope ...
You are welcome to visit to come and see why I use a modern DSO to diagnose faults ! I'm not sure I could have kept the machine working this long if I had to use an analogue (non-storage) 'scope. I can see no point in making the job harder than it has to be !
Did you notice the board behind the 'scope that has two rows of 48 LEDs ? It captures and displays one word time's worth of bits from two signals. It is mostly used to capture, hold and display the last value read from the core stores when a parity error occurs. The store test programs write a pattern of all ones or all zeros into memory locations, so the board makes identifying the faulty bit much easier.
I have great deal of admiration for the field service engineers who fixed these machines for real in the 1960s. Luckily I was able to learn from one of them when we did the original restoration work nearly 30 years ago.