Re: TV for oscilloscope

Michael A. Terrell wrote:
> cs_posting@xxxxxxxxxxx wrote:
> > Michael A. Terrell wrote:

> > > How are you going to open the CRT's glass to add the plates, then
> > > pump it back down, first with a vacuum pump, followed by a diffusion
> > > pump. Don't forget to install new getter material to flash while you're
> > > inside the CRT.
> >
> > Do they have to go inside?
> >
> > Obviously the further apart, the higher the voltage required, and the
> > dielectric constant of glass relative to air will change the field a
> > little bit, so it may not be practical to put them outside. Also there
> > might be a conductive coating on the inside or the outside?
>
>
> Typical deflection voltage is 300 VDC INSIDE the CRT.
>
> > Are there by any chance any moderately low voltage plates already in
> > there for geometric correction or anything?
>
>
> Why would there be?
>
> > Of course while messing around inside the TV is fun, it's also
> > hazardous. Here's an idea for something to do outside the box.
> > Imagine a stable waveform being displayed on a triggered scope, with
> > the horizontal sweep happening at about the same frequency as the
> > horizontal scan rate of a TV. Now imagine the rastering TV beam
> > sampling that frequency.
> >
> > Seems that for this one horizontal frequency, you could build a box
> > that had a ramp generator slaved to the vertical deflection, and a fast
> > window comparator. When the window comparator says the ramp voltage
> > corresponding to the current scan line equals the signal voltage at the
> > currant scan X, you turn on the beam. In actuality you will be
> > displaying a picture made up of one slice each of (#scanlines) periods
> > of the waveform, but if both the waveform and your trigger circuit are
> > stable, that's not a probem.
> >
> > Obviously this is limited in the frequencies it can cover, but at least
> > the vertical bandwidth is no longer limited by the coil inductance -
> > instead it's limited only by what you can see on a screen with a
> > comparatively low, fixed horizontal scan rate. Guess a multisync
> > monitor would offer more options than a TV.
>
>
> Obviously its a total waste of time. Find a surplus or used O-scope
> CRT to play with, instead. I've bought old tube type 100 KHz scopes for
> $2 to $30 at thrift stores and hamfests. Those worked. I've hauled home
> lots of dead scopes since the late '60s and fixed most of them with a
> handful of new resistors and caps, and sometimes a couple new tubes.
> You could fix most of them with a good VTVM and a schematic.

I dont think the OP could. This is a fine opportunity to make something
fun and learn lots. And end up with a basic scope.


NT

.

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