20-10-2020, 11:56 AM
Hi.
I don't see a plate resistor in the diagram. There is a cathode resistor of 470 ohms. Increasing the resistor will alter the operating conditions of the output valve. You are altering the bias on the valve.
Many people will make changes to a circuit to improve reliability but think this way. These amps were common and never known to eat 6V6s. Do you use it for hours every day? I suspect no so I'd replace the cathode resistor with the correct 470 ohms. If you really are worried the 6V6 then reduce the HT. You could add a 100 ohm 10 watt in series with the centre tap of the HT winding of the mains transformer that goes to chassis, this will reduce the HT a little but in all honesty I'd leave it as it should be.
I don't see a plate resistor in the diagram. There is a cathode resistor of 470 ohms. Increasing the resistor will alter the operating conditions of the output valve. You are altering the bias on the valve.
Many people will make changes to a circuit to improve reliability but think this way. These amps were common and never known to eat 6V6s. Do you use it for hours every day? I suspect no so I'd replace the cathode resistor with the correct 470 ohms. If you really are worried the 6V6 then reduce the HT. You could add a 100 ohm 10 watt in series with the centre tap of the HT winding of the mains transformer that goes to chassis, this will reduce the HT a little but in all honesty I'd leave it as it should be.
