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Depending on the plate voltage, you could need close to double the bias voltage to get it where you want. The real trouble is finding one that won't arc. Once it arcs without any glitch resistor, you'll find the dome grid wires have been burned through in at least one place and those sharp ends will now cause the arc to happen at much lower voltages than it took the first time.

When you run into this problem with those Russian surplus tubes, don't waste your time trying to get the amp repaired and working with the same tube. It will just come back. Reject the defective tube for the junk it is and hope you'll get a decent one on your next try.

[QUOTE="Shockwave, post: 754197, member: 10882"] Depending on the plate voltage, you could need close to double the bias voltage to get it where you want. The real trouble is finding one that won't arc. Once it arcs without any glitch resistor, you'll find the dome grid wires have been burned through in at least one place and those sharp ends will now cause the arc to happen at much lower voltages than it took the first time. When you run into this problem with those Russian surplus tubes, don't waste your time trying to get the amp repaired and working with the same tube. It will just come back. Reject the defective tube for the junk it is and hope you'll get a decent one on your next try. [/QUOTE]

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