Trouble with transistors

[Neurotic Norman]

Hello all! So, I've decided to take on a project. I'm not sure how many would be familiar with W. Grey Walter's tortoises, but that's what I've decided I'd like to attempt. Now, I thought I'd attempt it with solid state components for simplicity and ease of use. The only issue is, the schematic is VERY vague. I've tried a circuit simulator, but I'm having trouble making it cooperate. So I thought I'd come here and see if anyone had any ideas as to what one could help with the conversion. I'll attach the schematics and a description of operation.

Here's the theory of operation: http://www.beam-wiki.org/wiki/Grey's_Turtles

Thanks in advance!

[German_EE]

The first problem are the two grids, I know that a triode is a rough equivalent of a transistor but it has been years since I built something with a tube in it. Secondly there is the behavior detailed in the link you gave, it's so complex that a complicated transistor circuit could easily be replaced by an eight-pin micro and then the code modified to suit.

If you DO find an equivalent circuit then please let us know but I suggest you save your sanity and use a microprocessor.

[Neurotic Norman]

I see it didn't post the first time. I have a circuit that'll work. It's just not annotated. None of the resistors or capacitors have values. I thought I attached it to the first post, but I'll try on this one.

I think the microprocessor approach might end up being six of one, half a dozen of the other. Unless I can find someone that can program in a language that's a little more up to date, I'll have to figure that one out too.

[T3sl4co1l]

That screen-and-grid connection is peculiar.  A rising step change at the first tube (which is triode wired) will tend to maintain conduction in the second tube.  But a falling edge will tend to turn it off (firstly because screen and grid voltages turn off), but after some time (determined by the grid RC time constant), the rising threshold will be lowered.

I don't think it implements a "zero crossing tracker" sort of characteristic, but it's kinda sorta like that.

Tim