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Re: 6SL7 STRESS TEST CONCLUSION

Posted by Lew (A) on May 30, 2002 at 13:09:43

In Reply to: Re: 6SL7 STRESS TEST CONCLUSION posted by Al Sekela on May 30, 2002 at 07:57:38:

One question salient to my post was whether the CCS tube itself is subject to the constrained current draw of the other elements of the circuit for which it provides constant current. You imply the answer is yes, and this would nicely serve to prevent or deter thermal runaway. I would have thought that since the current source tube itself is responsible for the constancy of the current, it is not itself protected from thermal runaway due to ITS positive grid current. Your experiment suggests I am wrong, but I don't quite know why. Clearly, one could run the dual-differential and cascode sections of the Atma-sphere input circuit with marginal negative grid bias or even slightly positive grid bias without fear of a problem, due to the action of the CCS; I just did not think the CCS itself would be protected. These are some of the neat things one discovers by doing experiments to investigate stuff not easily found in textbooks or hobbyist magazines. I do still wonder about the consequences of repeated on and off cycling, and I think you were wise to advise others not to extrapolate your results too far.

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