>
>Hi Carl:
>
>Yes, SPICE would work for tubes as well as transistors. However, it is a
>lot cheaper to build up a model and test it. Tektronix, right in your back
>yard, built a marvelous tube curve tracer that allows you to build up a
>circuit and model it on a scope - running your own curves. Unfortunately,
>these old classics are now being gobbled up by the audio tube fanatics who
>pay up to $5,000 apiece for them.
>
>It might be a little awkward breadboarding a 5,000 volt tube circuit to run
>curves - but you can do the same thing by hand. Recently, I wanted to
>determine the effect of varying screen voltage and control grid voltage upon
>a tube. None of the books had curves for what I wanted to do. So, I
>grabbed a 6L6, put it on the table with a couple of hundred volts on the
>plate and varied the control grid voltage while monitoring currents for all
>the elements. I did this for various screen voltages. Thus, I created my
>own curves.
>
>Although a 6L6 is not the same as a 4-1000, it is a beam power tube and will
>have traits similar to an 813. and, the direct current characteristics of a
>6L6 ought to be of sufficient to draw preliminary conclusions on how a
>4-1000 might act if all the voltages are proportionally increased. And, the
>gain could be tested at audio frequency rather than rf.
>
>Of course the better solution is to build the circuit, fire it up into a
>dummy load and change the variables - denoting changes made. After
>determining the results, you can right a computer model that will be
>consistent with the results you have already obtained. Then, sell the model
>(whoops, tho only people who would want the model would be hams - who are
>cheap to buy modeling programs).
>
>On second thought, it might be easier to get a part time job at $8 per hour
>and after 1,000 hours you would have enough money to pay taxes and have a
>nice shiny new Alpha amplifier.
>
Mo' money does not necessarily equal mo' betta. The shiny new Alpha is
quite likely to have: RF-actuated bias-switching (switches to non-linear
bias during soft-syllables) and no speedup circuit for the vacuum relay.
(protects the vac. ant. relay from hotswitching with quick radios) . .
>
later
>
- Rich..., 805.386.3734, www.vcnet.com/measures.
end
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