Back to the HP 200CD. Since I haven't had any experience with tube
electronics in the last 50 years, I'm a little rusty on some of the
subtleties of component specifying. I've been looking at the electrolytic
capacitors in the circuit diagram and my stock with an eye to simply
replacing all of them in an effort to resurrect the instrument to "near new"
condition.

I have (or can get) an exact replacement for the 100 uF 100V non-polarized
capacitor. That's the easy one.

There's a 40 uF, 450 V as the final filter in the Power Supply filtering. I
can easily get either a 100 uF 330V or a 33 uF 300 V. The DC working
voltage for this is 170V so it would seem that the original 450V may have
been based in part on inventory rather than exact electronic need. Is this
reasonable?

There's a three section filter cap in the Power Supply, each section of
which is 10 uF at 450V and the working DC voltage is 310V. I have some 20
uF 400V Polypropylene capacitors that would fit. Are these reasonable
replacement or should I just order the "correct" values from somewhere?

There's a .082 uF 600V Paper capacitor that's part of an RC filter to a tube
grid that works at 20V DC. Would a .082 uF 400V Mylar be an adequate
substitute?

Finally, there's a capacitor that connects the Low output terminal to
chassis ground (there's also an optional external strap as well). The
schematic shows this as 40 pF , "adjusted at factory for optimum
performance. Average value shown. Part may be omitted." The parts list
gives this as a 1.5 pF Titanium Dioxide capacitor. There are three
strategies that I see he
1. Leave it in place
2. Remove it
3. Remove, measure, and replace with a mica capacitor of appropriate
value
What's the best choice?

Also, assuming that I replace all 5 tubes with new ones and replace the
electrolytic capacitors, and clean the unit, are there any other
before-testing substitutions that should be made?

TIA
Norm