Oscilloscope Z axis?

Discussion in 'General Electronics Chat' started by autorelease, Nov 9, 2009.

  1. autorelease

    Thread Starter Active Member

    Jan 26, 2009
    I've built a little circuit that "draws" by generating X-axis, Y-axis, and Z-axis (intensity) signals. When hooked up to my Leader XY monitor, everything displays fine, including the Z-axis blanking.

    However, when connected to my Tek 464 scope, I see very little modulation of the beam intensity. The back of the scope says "positive-going input decreases intensity, 5V P-P causes noticeable modulation at normal intensity." So I'm using 0V for "beam on" and 5V for "beam off," but the modulation is in no way noticeable.

    So there are a few possibilities:
    1. I'm not using the scope correctly, there are other settings on the panel I need to change.
    2. I need a higher input voltage to blank the beam. This would complicate things.
    3. There's some trimpot inside the scope that I need to tweak to adjust the Z axis gain.
    4. The scope's Z axis is broken.

    Anyone familiar with old Tektronix scopes have an idea?
  2. KL7AJ

    Senior Member

    Nov 4, 2008

    Run a clip lead from your scope calibrator to the Z axis input. Set the time base to 1ms/sec, Auto mode, and you should see a nice "chopped" horizontal line. If so, your Z-axis input is working. If not, then...well...it's not!

    While you're at it....here's an excerpt from the Opus of Amateur Radio Knowledge and Lore I think you'll like:

    Fun and Perverse Things to do with your Oscilloscope
    All work and no play can make Elrod a dull boy. An oscilloscope can keep you entertained in the shack when the bands are dead. Most dual-trace oscilloscopes have what’s called an “X-Y mode.” In this mode, the internal time base (sweep) is disabled, and one channel is converted into a horizontal deflection channel. If you have two signal generators, you can create circles, figure eights and all kinds of interesting, loopy shapes. These are known as Lissajous patterns. If you ever watched the old Outer Limits series on your black and white TV, you saw Lissajous patterns when the creepy-sounding announcer intones “Do not adjust your television set.” (Being the sort of non-compliant lad I was, I readjusted my television set anyway, just for spite).
    Now, if you want to get even trickier, you can create a clock, characters, or even pictures on your oscilloscope screen with the X-Y mode. Or, you can go all the way and make a television out of your oscilloscope, if your ‘scope happens to have a “Z-axis” input, usually cleverly hidden on the back of the cabinet. The first time I saw a green CRT TV, not only I was impressed with the cleverness of it all, but was even more impressed with the amount of spare time the creator thereof had at his disposal. (Not only did this guy have live video on his ‘scope, but could, with a single knob rotate the image any amount he wanted, or even flip it over. This was long before anyone I knew had anything resembling a computer).
  3. autorelease

    Thread Starter Active Member

    Jan 26, 2009
    It seems to be working. Turns out that I just had to turn the intensity knob way down. The picture is pretty dim with a 5V unblanking level; I might have to use 9V or 12V to get a brighter picture.

    As for the "scope TV," what I've done is pretty similar :)