The valve option

[humorist2751]

Greetings to all.

For the delectation of interested parties, I believe the attached may be the EF50-based circuit referred to by Danny. It is part of a project published by Radio Constructor, this part of the project appearing in the October 1953 issue.

The project as a whole was called "The Pattern_Master"; not surprisingly it was a TV pattern generator (405 in those days, naturally).

[Danny]

Hi arrr thats the curcuit he gave me but i didnt know where it came from in the first place i must email my friend to get the rest as this could be usefull when i have to build the master sync generator for the flyingspot scanner!. hopefully i can have a play this weekend if she dont catch me that is. ive got lots of chores to do .
But the origanal cercuit was based on a ham project and i altered it a bit to try to get it to act as a modulatorfor video instead of a beacon!.
Danny

[DoctorWho]

I know this is going a lot further, but has anyone considered building a valve standards converter without any solid state circuitry? I'm guessing it would be enormous, bigger than the solid state unit Gerry Wells has, but how easily could this be achieved? I have a picture of the optical converter used by the BBC, but I was thinking more along the lines of all electronic, but all valve circuitry. Just a thought.

[ppppenguin]

Originally Posted by DoctorWho

I know this is going a lot further, but has anyone considered building a valve standards converter without any solid state circuitry? I'm guessing it would be enormous, bigger than the solid state unit Gerry Wells has, but how easily could this be achieved? I have a picture of the optical converter used by the BBC, but I was thinking more along the lines of all electronic, but all valve circuitry. Just a thought.

Even the professionals shied away from this. The first all electronic converter, the BBC CO6/501, is a massive lump of analogue electronics. While I'm sure it might be theoretically possible to build something like this with valves you are talking about something on the size and scale of early valve computers though it would be largely analogue rather than digital.

As for a digital converter, the amount and speed of the logic would make it extremely difficult with discrete transistors let alone valves.

If you threw enough resources at the problem you could probably get an answer, rather like NASA threw resources into the computers for the Apollo missions to achieve results that looked pretty much impossible.

[jim_beacon]

We had some valve standards convertsers at work, for turning polar radar displays into raster scan for the addition of secondary radar labels. They used a special converter tube, which was effectively a camera and picture tube in one envelope. The writing beam wrote onto a charged plate, which was then read by a second electron beam.

Jim.

[ppppenguin]

Originally Posted by jim_beacon

We had some valve standards convertsers at work, for turning polar radar displays into raster scan for the addition of secondary radar labels. They used a special converter tube, which was effectively a camera and picture tube in one envelope. The writing beam wrote onto a charged plate, which was then read by a second electron beam.

That's cheating! It's just a souped up version of pointing a camera at a monitor. Doing polar to rectangular scan conversion in electronics is a lot harder than just changing the number of lines.

Just a thought, I wonder if the Williams tube (used for memory in some very early computers) could be pressed into service as part of a valve digital converter. This is not a serious thought!

[DoctorWho]

Going from a purely analogue angle, how easy would it be to build a valve converter which quite simply removed every 3rd line?

Obviously a total valve based converter is possible, but I do have to wonder at the size of it.

[ppppenguin]

Originally Posted by DoctorWho

Going from a purely analogue angle, how easy would it be to build a valve converter which quite simply removed every 3rd line.

Very difficult. Because each remaining line has to be stretched from 64us to 99us. This needs storage of at least 1 whole TV line. In digital designs this is memory (and very little by modern standards), in Darius's design it's charge coupled delay lines, in the BBC CO6/501 it was 576 individual L/C networks and a pair of single pole 576 way switches. That's actually a gross simplification of a very complex bit of circuitry.

BBC engineers didn't even attempt an electronic converter until transistors were capable of operating at video bandwidth and their solution was a pretty massive "state of art" design in the early 1960s. It might have been theoretically possible with valves but the number of valves would have been into 4 figures. The sort of thing you would only attempt with military necessity and budgets.