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Light Bulbs Do Not Have Constant Resistance

The dimmer the light bulb gets, the *lower* the resistance across the filament. When not glowing, the resistance drops down to several ohms.

When powering up the amp, that's when the bulb should glow its brightest. And afterward, it should get dim to the point where it's barely glowing. A single 100-watt bulb generally does the trick with moderately-powered tube amps.

You may also want to try a 220-volt bulb for such an application (110-volt circuit).


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