I checked my working scope this morning. I wish we could do inline pictures. I reviewed my tear down pictures and found that I had a shot of the DTP knob before I took it off, and am 99% certain that it's in the full ccw position. The new (parts) one is SN 29XXXX, the "old" working one is 31XXXX. The 29XXXX is at 0.35, the 31XXXX is at 0.25. Interestingly the 29XXXX has the fine dial setscrew at the "1" position. The 31XXXX has the setscrew at the "3.5" position. That's funky, but not really relevant?
I also wonder about the history behind these "min" settings. There's got to be some engineering behind it.
I don't recall them being non-zero back in my Army days. My experience, in general, is that there's not a lot of use for the B-delayed trigger. Perhaps more so in broadcast TV? (As another aside: in my profile picture I'm using the B-delayed function to examine a GHz radar transmit pulse triggered from a 20kHz system clock. Funny the things you remember). In any case, I don't recall the zero or values on the knob were of any interest. It was just a device to move the B-delayed signal under examination. This could be entirely my experience and use case only. I would be interested in learning what use cases in which values from this pot are needed.
Is this style of multi-turn pot just a means of obtaining fine delay control over a very large range? The ability to have nano-second resolution over a micro-second (or mili-second?) range. 1000-1 is a pretty large range.
Also interestingly, the other scope visible in my profile pic is a Tek 491 spectrum analyzer. I recall that it had a crank-knob on it. I was reviewing replacement knobs on the sphere site and came across that knob and all these memories came flooding back. I remember cranking on that thing to slew the spectrum analyzer across several orders of magnitude of frequency. So I wonder if these are just devices for handling fine control over a large range.
Dave
Dave Peterson