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Our friend Gio from DIY Audio Projects has sent in a cool Push-Pull Tube Amp Build. This tube amp fits into a 8 X 12 inch chassis and looks fantastic! Now if only we could find a drugstore with a tube tester. With cool equipment like this and tube TV troubleshooting guides popping up there is sure to be demand for tube testers once again? "The basic design has been around for a long time (50 years or so). The problem with early applications was that it was difficult to force it to operate in a linear manner. It can only function in a class-A mode with both tubes always conducting. The reason this circuit is attractive is that it eliminates the need for a phase splitter stage. It requires only a single-ended driver. The advent of solid state electronics provided a solution to the problem. A simple application of a common LM317 IC voltage regulator converts it to a very accurate constant current source (CCS). Using a CCS in the cathode circuit of the SIPP stage forces it to operate in class-A. What was a sort of a mediocre output stage thus becomes highly accurate and quite excellent."
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You might remember Michael Saunby, he was the guy that had the interesting clock that we were trying to determine heritage for. The clock was almost featured on Antiques Roadshow but unfortunately was left on the cutting room floor. Michael works with lots of antique electronics and this 1930 vintage amplifier and speaker is a great example of what can be done with a mix of old and new. "The original amplifier was typical for a 1930s broadcast receiver, a single ended pentode with tone correction. The valve chosen was a high slope pentode type AC/SP3; as used by the BBC in pre-amplifiers from late 1930s through to the 1950s."
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Back in 1959 this is what you would have been reading if your were an electronics professional. How things have changed from then to now, almost everything you purchase today is made to be disposable since you can produce a new board for less than it would take to troubleshoot and repair it. It is impressive how reliability has changed though since in this article they expect most people to spend at least 40 dollars per year on service calls to repair the TV, at only 5 dollars per service call this means that your TV is expected to break down every month and a half!
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