On Sun, 2 Mar 2008 07:49:53 -0600, "Tim Williams"
wrote:

Ah yes, I do that when tracing tube curves.

Setup:
- Isolation transformer with series current sense resistor and diode
(1N4007) connects to tube plate/cathode
- Variable negative supply connects to grid/cathode and voltmeter
- Scope to plate (10x probe) and sense resistor, X-Y mode
- Camera pointed at o'scope, as square as possible! (Tripod sits in front
of the bench, so it's about 2-3 feet away. A couple X optical zoom is
enough to fill about half the shot's area with the CRT, reducing spherical
abberation that otherwise comes with a tight shot.)
- Take one shot for every grid voltage you want recorded

Later...
- Crop images
- Draw curves of one bright solid color to fit the trace, and lines of
another color to fit the graticule (if set up well, you should notice the
lines are evenly spaced and have little slope, only a few pixels across the
whole screen)
- Strip away colors less vivid (the original image)
- Superimpose all the line drawings, add labels and finally, save as .GIF.

A lot of steps and hand work, but not bad for having everything on hand.

Tim

The other thing I like to do is to stick a Post-It to the edge of the
screen, and note the date and the parameters of the display, maybe
even sketch a little circuit or something. Helps keep the photos
organized.

John