Quote:
Originally Posted by Radio Wrangler
You can do a similar trick by distributing several valves down transmission lines rather than having them in simple parallel. You can build a much faster Y amp this way and now you know why some Tek scopes had a hundred valves in them.
Scopes are fascinating, and the programs are better than on TV.
David
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Indeed. The 545A has a fully differential Y amp, which includes 6 DK6's on + and 6 DK6's on - in a distributed transmission line structure. They feed into a delay line to slow down the vertical signal to wait for the timebase to get going. That itself has fifty adjustable capacitors (and two inductors) that have to be tweaked in sequence to optimise the rise time.
The fastest plug in amplifier of the day was the Type L, which pushed the 545A to its limit bandwidth of 30MHz. The fastest of the valved scopes (well actually a hybrid with some transistors) was the 585. Tek tried hard to break the 100MHz barrier, and failed - the 585 makes 85MHz.
But sampling plugins like the very easy to use 1S1 takes any of those plug-on scopes to 1GHz.
The distributed amp concept came from Howard Vollum (Tek's founder) and David Hewlett (HP's co-founder) having dinner together and sketching ideas on a table napkin. They were good friends in competition.
Craig