>"The self contain HV probes are easy to change polarity. Either
>reverse the meter leads, or connect a small bridge rectifier between >the
>meter and the probe and ground lead. "
Not so fast. These things had a current detect function for the horizontal output TUBE (vale for those overseas). Now if you put a DPDT switch there and reverse the meter coil polarity that would work.
However, a bridge rectifier would introduce error, and that error would be greater at lower voltages. Many meter movement barely need a volt but a standard diode drops .6 of that. At scope cathode voltages which might only be like 2 KV or less, this is significant.
We now have a Keithley HV probe but acn't really use it. Dude found a good deal on it, but it has a 350 meg output resistance which means you need an electrometer to use it. A regular VTVM will not work without alot of math, and even then... We do have one meter is would work on and it is seriously aged. (two syllables there, really) Actually it agrees with the best of the Flukes we got, but nobody is going to do the NIST routine on it and certify it.
I have seriously considered building one, but not with 1090 megs. The meter is 10 megohm, so 90 megs gives it enough range to measure scope CRT voltages. We are sort of committeds to repairing and restoring CROs. I do not like DSOs, let alone LCD based scopes. I believe that every electronics class in highschool should have a CRO for the kids to play with, once they know enough to not fuck it up of course. I also think they should not graduate without certain other knowledge, like the different types of firearms ad how to at least unload them and make sure there is not one in the chamber. If we are going to have guns here, dammit, make sure people know how to be safe with them.
They should know how to change a tire on the care, some at least simple mechanics. How many times has someone called on a neighbor or whatever to do one of the simplest of tasks claiming that are "not mechanically inclined" ? We put a Man on the moon and now we are down to this ? No wonder conspiracy theorists think it was fake.
But I can tell you the moonshot was real. Not that I was there but it is not hard to figure out. This was a milestone in human history, a worldwide event. There were Russian kids with telescopes all over the place and it was during the cold war. If ANY ONE of them caught even one little piece of evidence that it was faked they would be rich and the USSR would have never let us live it down. And if you really think about it, and I mean really, it would have cost more to fake it than to actually do it. Plus they really did want to do it.
But I have digressed quite a bit. As I look at my old 561A Tek that was built before I was born with dual trace and dual time base, sometimes I wonder just how far we have come. They have minuturized things and packed more transistor and other devices into one case, but what have they really done ?
When I was young my Uncle gave me the basic books from the air force. Whatever branch of the US military you serve(d) in, if it was the air force you usually had the least risk and got the best jobs when you got out. At least back then.
But those books said there are only three electronic circuits, rectifier, amplifier and oscillator. And every circuit to this day you see can be described as one of those. It might be gated or controlled, fancied up in all kinds of ways but it is still the same thing. Consider the function, a computer gate can be considered rectifiers feeding an amplifier.
But anyway, I am probably boring the OP (et al) so it is time to stop.
To the OP, do you got 15 volts ? Do you got 130 volts ? Before tearing into the HV shit that doesn't like to be touched, make sure you got everything else.