GT-40 etc.

[Paul Koning]

> On Jan 20, 2018, at 11:06 PM, Ethan Dicks via cctalk <cctalk at classiccmp.org> wrote:
> 
> On Sat, Jan 20, 2018 at 8:32 PM, Paul Anderson <useddec at gmail.com> wrote:
>> I think just the VR12, VR14, and the VR17.
> 
> OK.  I've never had any of those.  I'm more wondering what modern
> tubes might work.

Remember that the GT40 is a vector drawing display, not a raster scan.  So you need a tube and associated deflection machinery that can handle high frequency X and Y deflection waveforms accurately.  This is not easy, especially with magnetic deflection.  I don't know what DEC used; CDC did it both ways with the 6000 series consoles.  The original ones had "dual radar tubes" with electrostatic deflection, hairy circuits with 3cx100a5 final amplifier tubes.  The next generation, in the 170 series, had a single large tube with magnetic deflection but still random access vector drawing.  How they did that with magnetic deflection is not clear to me, it sounds hard.

	paul