My glue job on the B-delay switch cam was doing really well. I reassembled the switch assembly, attached the A and B knobs (B knob now solid as a rock after re-gluing the plastic and body), and figured out how to align it all. It was working like a charm.
Over the last several days I've gotten my blown C1419 replaced, reassembled the vertical input assembly and so on. Today I was trying to get the A7 board back in and it was giving me a devil of a time, but I got it in. Only lost a little blood. Reattached the A Time/Div knobs, and while attaching the B knob things started going bad. I don't know what did it - I wasn't being harsh with it all. But I realized it had failed again, so I had to take the A7 out again for the 3rd time. Disassembled the Time/Div switch cams and sure enough: the B cam was gone.
All my glue work held fine. It was the rest of the plastic cylinder that crumbled. The good thing is that it's all fallen out of the cam now, including the spring. So I can now see how it's put together. I'll have to build something. I'm not really sure where to begin, but I'll sleep on it. I'll document what I do for posterity.
I haven't had a chance to review the part numbers and variations with serial number. I did find another difference between the manual I have and this scope. It's quite apparent there were a lot of changes. If I want to know this model well there's a lot of history I'm going to have to learn. I would like to learn the part number variations for this cam. It seems a common failure, so it'd be good to know what to look for. I'll keep the "wrong" one I got. The seller is willing to take it as a return, but I have to pay shipping. Might as well keep it. Maybe I'll sell it myself down the road, if I don't end up using it some day.