AFAIK, the 465M borrows heavily from the 455 and as such I wouldn't be tempted to call it a Hi-Rel or ruggedized 465-like 'scope. I think this has been discussed a while ago on this forum as well. Maybe the 465M just inherited the 455's trigger circuit? I haven't checked schematics though. I'm not at all familiar with MilSpec etc, so I can't correctly interpret the 465M's description in the Tek catalog.I was unaware of the connection between the 465M and the 455 until recently. I
have since updated my notes to place the 465M with the 455 as a separate group.
I think your assumption that the 475(A) and 485 have always been equipped with tunnel diode trigger circuits is correct.I think this makes sense from a performance point of view. My guess is that
Tektronix did not have a 200+ MHz integrated trigger until the 7B80, 7B85, and
7B92A which was sometime after the 475 and 485 were introduced. I do not have
exact dates on those because I have not gotten that far through the catalogs. :)
The 468 uses an IC trigger circuit.So it does. Thanks for pointing this out.
Somehow when I originally checked the schematics, I decided that the 468 used
tunnel diodes. Now I am not sure how it is related to the others. I has the
integrated trigger of the 464 and 466 but the fast sweep and introduction date
of the 465B.
From what I see on the most popular Dutch used-equipment sites, there's about one 465B on offer for every 465.This is why I do not anticipate getting one of these oscilloscopes. On one
hand, I am not fond of mixed sweep. On the other hand, the 465B, 468, and 485
are the only ones with alternate sweep. On the gripping hand, those are either
complicated or rare.
If one falls into my hands I will repair it but in the meantime I have my 2230.