What happens when tubes go bad

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Do It Yourself (DIY) paradise for tube and SET project builders.

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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Michael Percy Audio

Topic - What happens when tubes go bad - vetmedrobert@gmail.com 10:32:04 03/22/12 (3)

RE: What happens when tubes go bad - vetmedrobert@gmail.com 16:48:10 03/24/12 (0)

The coating on the cathode is burned off by the filament or either the filament is burned up - grhughes 06:50:40 03/24/12 (1)

RE: The coating on the cathode is burned off by the filament or either the filament is burned up - vetmedrobert@gmail.com 08:41:32 03/24/12 (0)

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