[GreenKeys] OT: Need help to T-Shoot this Tek 485 scope

[drlegendre .]

Paul,

Yes, I know exactly what you're talking about and that's a very good
suggestion. If you have the Tek 485 manual they're R1603,04,05,06,08,09. I
think they use multiple parts as to avoid exceeding the Emax of the
resistors, which is typically around 600V. One thing so far - I can find
the parts on the drawing, but not on the machine. Tek says they are on
"transformer board A15" but no such board exists, at least in the docs!

But either way it's a very high-Z circuit and any kind of leakage or other
trouble will spoil it..

Now what I +really+ need to know, is what voltage should the g1 have vs.
cathode? IIRC, I read -9V on g1, so at least it's proper in the sense that
it is negative - but what should the actual value be? And what would I
expect to measure with a typical (11M Zin) DVM? I mean, the overall accel.
potential in that tube is like 21kV (18kV anode, -3kV cathode) so I'd
expect to see a whole lot more than -9V bias, eh - or am I way off base in
my assessment?
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