"Jim Adney" wrote in message
...
On Fri, 17 Sep 2004 15:58:23 GMT "Norm Dresner" wrote:

I have an HP200CD that needs some loving care. The manual says to
measure
the difference in the voltage between two different points in the
circuit --
it shouldn't be all that much but the voltages between these points and
ground is in the hundreds of volts range. The manual also says that I
should be using a meter with 220M ohm or greater input impedance to make
the
voltage measurements. Any suggestions where such a beast could be
bought/rented/stolen?

There are such devices, but any modern DVM with a 10 MOhm input
impedance will work just fine to measure the voltages in your 200CD.
That warning is there because when the 200CD was made the common VOMs
of the day had much lower input impedances, so HP wanted to keep you
from using those.

I've worked on 200CDs with 10 MOhm meters with complete satisfaction.


Jim

Thanks for the encouragement. I've almost decided not to try to repair it
but to build a modern, solid state oscillator using the mechanical
components as the basis. The dual variable capacitors are an almost
impossible item to find and there's more than enough space in the chassis
for anything with transistors or IC's. And, as a bonus, the bottom of the
interior foundation should serve to isolate the incoming AC from the
sensitive circuitry in the upper compartment.

Norm