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I set up a 6N30Pi tube as the driver stage using a CCS. Looking at plate curves on Steve Bench's site I used 10ma, -5 volt bias. This should result in a plate voltage of around 90 volts. Only problem is that I end up with ~43 volts, both plates. The same settings allow me to run a 6BX7 at about 80 volts, which I have done and I get the 80 volts I expect. Unfortunately I only have one 6N30Pi to play with, does anyone have any idea what is going on here? TIA
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Reading up on these phenomena I decided to let it run in a circuit with a signal and after 3 hours or so plate voltage was up to the 90 volts I expected. Probably the cathode needed reforming? Thanks for your help.
There is also the problem of gas. The 6bx7 is a more robust tube but it's difficult to find a tube that is balanced from side to side. This is true of any high perveance tube like both the ones you cited. Ray
"The gift of imagination is a gift of the Gods imparted to a few who receive innumerable kicks in the a$$ their entire life." Le Corbusier (Charles-Édouard Jeanneret)
You are right about the 6bx7, the first one measured 80 volts on one plate and 110 on the other!
As far as gas goes is not that what the getter is supposed to deal with? The tube has abundant silvering so I would imagine there is no problem there.
Heater glows, and the tube gets plenty warm so I imagine this is not a problem.
So I imagine it must be low cathode emission. I am unsure just how this works to lower the plate voltage. Plus this is a relatively new tube not previously used (as far as one can tell from anything coming from Russia). So I am puzzled how it is that the tube could be defective. Anyway, thanks for giving me something to think about.
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