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It is that easy. I'm told it's also easy for the crt to go bang due to the electron stream overheating the glass at the neck.

NT

yeah, it's about that easy. but one of those $25 pocket digital osciloscope kits might be more useful, a TV oscilloscope can barely handle audio frequency signals.

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dakupoto:

You don't end up with a scope but a fairly useless curiosity which you may or may not find amusing to play with. The only way to turn a CRT into a proper scope is to use it as the display for a conventional digital scope - this probably isn't worth the effort any more. Every now and again I see huge CRTs being dumped at the local tip and I have urges to rescue them and put them to work but I'm getting over it :-)

MK

the timebase is 15kHz, and the video bandwidth 6MHz.

NT

On 14 Oct 2015 09:50:15 GMT, Jasen Betts Gave us:

It would be like first year electronics experimentation regimen.

Not unlike building a crystal radio tuner by today's standards.

Better off buying a USB scope and using your PC display to examine the probings.

And in oscilloscope mode, you need the vertical deflection to respond at the video rate, not just the intensity.

Magnetic deflection produces much better focused spots than electrostatic, but is much much slower. The reason for the badness of electrostatic focusing is actually pretty interesting: because the field obeys Laplace's equation, it cannot have a maximum value except at the boundary. Thus you can't make negative lenses, which means you can't correct aberrations.

Cheers

Phil Hobbs

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Dr Philip C D Hobbs 
Principal Consultant 

That was one of the first projects I tried as a teenager. As you suggest it was severely limited in bandwidth. Looking back, it might have been a lot better with compensation for the coil inductances. I guess a current driver with as high an available voltage as feasible. Or just pre-emphasize the signal I suppose.

Then I got an actual scope and the first thing was to make it show a TV picture :)

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John Devereux

Oscilloscope/

Oscilloscope/

You can use them as finals in audio amplifiers, apparently. I haven't done this, but I'm assuming that you get both sound and light from the effort.

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Tim Wescott 
Wescott Design Services 

You can run it both ways, depending on the bandwidth needed. You can also use an envelope detector to go even higher in frequency - at least for some apps.

Can concentric rings with opposite polarity not achieve that?

NT

OR

Not sure if it is that easy -- so I ask.

Nope. The potential always achieves its extreme values on the surface, so there's no way to have a maximum in the middle, which is what you need for a negative lens.

In optics optics, you can compensate for field curvature by keeping the Petzval sum small--see

, but this doesn't work in electron optics, because you can't make the equivalent of negative lenses. It's the classical problem of electron optics.

Cheers

Phil Hobbs

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Dr Philip C D Hobbs 
Principal Consultant 

What happens if we make the electrode a spot right in the middle, where the beam would hit it, then deflect the beam away with a magnet just before it does hit it? I can see this not working :)

NT

That is total bullshit, and i am being polite.