Fun oscilloscope (filament transformer) was: Re: tube synthsizer

[Rick Jansen]

In message <199910280632.IAA04563 at window.intermetall.de> you write:

> That's true, but I found that transformers with that voltage ratio,
> or filament heater windings are hard to get these days (at least where
> I live), and also good tube sockets. 

I built a simple oscilloscope 15 years ago, with a very big oscilloscope
tube (22 cm across). Couldn't find a 6.3V transformer either, used a 6V
standard resin encapsulated black plastic "cube" instead. Works fine. Do 
check that the secundary and primary windings are insulated well enough 
against the voltages you use!! I generate the high voltage with a diode
and capacitor "ladder". Isn't that a circuit invented by Mr. Graetz...?

I drive one X and one Y plate with voltages derived directly from the net,
thru an R/C network for phase shift. Result is an adjustable ellips.
The other X plate is driven from a small audio amplifier and another one of
those very small black plastic resin insulated transformers. I drive the
secundary with the audio signal, the "primary" drives the other X plate.
Result is an ellips with an audio signal imposed on it vertically.

You could also drive the X and Y plate with a stereo signal, to monitor
phase differences between left and right :-)

Rick Jansen
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rick at bpa.nl rja at euronet.nl   http://www.euronet.nl/~rja/
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