Bias Problems

knowledge base for the classic Dynaco ST70

Postby TomMcNally » Tue Dec 05, 2006 11:30 am

Hi Jason -

Yep - sounds like a bad tube, one trick that has worked for me a few times is check the filament pins on the tube and hit them with a soldering iron, sometimes the solder joint is bad and the filament opens up.

Anyway - you can test with another tube, although a pair of something else would be preferable.

... tom
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Postby dhuebert » Wed Dec 06, 2006 9:30 am

I bought several E-H 6V6 recently and they biased up all over the place, one tube would be 30mA and the next would be melting down at 75 mA. Since then I have heard complaints from others about QC issues, my question is: do other E-H tubes have problems as well? Was it just a bad lot number or have you guys had problems too? I tell you, I put a random pair of Sovtek 6L6GB in my latest, at idle they were both 35mA (fixed bias) and at full throttle one was 65mA and the other was 67 mA. Did I get lucky or are these just great tubes? This corresponds to my general experience with Sovtek. I have some E-H EL34 that I have yet to fire, are they gonna be any good?

Don
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