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Data sheets for the 6BX7GT and 6BL7GTA say that when using these tubes in vertical deflection service, section 1 should be used for the oscillator. The Tung-Sol 6BL7GTA sheet further states that the tube has "an improved section 1 for increased life as an oscillator..." Does anyone know exactly what the difference(s) are between the two sections in these tubes? Interelectrode capacitance is only the tiniest bit different, and other specifications such as mu and Rp are identical. The two anode structures also look identical from the outside. What could the manufacturers have done to make one section electrically more robust without changing specifications or visible appearance?
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Most of the modern versions of these two types have a g1 radiator on one of the sections and none on the other. I assume that the section with the radiator was intended to be the output section and the radiatorless one the oscillator.....but never bothered to visually trace it out to confirm.Edit: Got curious so checked my stash. Turns out there's a topside g1 radiator on both sections of most versions. There's an additional bottomside g1 radiator on section 1 of Sylvania and GE GTA versions but not necessarily on the plain GT versions. So my assumption that the output section got additional cooling was wrong: it's the oscillator section. Wonder what's so stressful about oscillator service.
Edits: 03/23/17
I looked at several of mine but didn't see that difference. A small additional radiator would explain why the two sections otherwise seem to be electrically identical. As for the usage, I would expect the oscillator section to experience a higher duty cycle than the section used for linear amplification.
I'll take another look at the tubes in my stash this weekend. Thanks for the info!
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Buy Chinese. Bury freedom.
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