The hardest part to build on an oscilloscope (while still maintaining
bandwidth) is the final deflection amplifiers.
Something had occurred to me a little while ago. There is a readily
available supply of chips that will do the job in a specific product. That
product is CRT SVGA monitors.

The video amplifiers that drive the grids of the electron guns.

Normal supply voltage is 80 to 100V.
Normal output swing is 10 to 75V or 10 to 95V
Normal signal input voltage 0 to 5V
They are capable of driving 8pf loads which is close to the value of a
deflection plate.
Output response times are 10us or faster. Some of the newest are down to
2.5us.
Corresponding bandwidth is DC to 50 or 200MHZ
They normally come in a self contained package that contains three
amplifiers.

Since most scope most scope tubes take less than 80 volts per plate for full
deflection (all the ones i have seen), then they make a great deflection
amplifier.

They would be great for upgrading an old tube type scope up to a solid state
100Mhz unit. The rest of the amplifier chain would be easy to built. They
would also be great for building a scope from scratch. Remember to keep lead
lengths short, and use shielded interconnect cables, because at 100Mhz it
will oscillate if it can hear it's self.

That is what I am currently doing to an old EICO scope. I already have the
vertical amplifier in place. It uses two sections of a VPS10S. For The
horizontal amplifier I am going with discrete components, because it doesn't
need to be as high of bandwidth. I have got the horizontal amplifier built,
and I just need to get it mounted.

The next stage is the amplifier stages between the input, and deflection
circuits. They are all going to be 5V rail to ground. There will be a couple
+10 and -5V point in the circuit for level transition, and signal
inversions. And I have to build the horizontal oscillator and triggering
circuits.

The only thing that has been bugging me is, what can I do with the old tube
sockets. I have been trying to think of some tube circuits I could use. The
only things I could think of is a high impedance input buffer. Or use a 6AL5
as a wide band RF rectifier. Or I could put in a sweep oscillator and a IF
amplifier and make a rudimentary spectrum analyzer.