'grid feed resistors to the output tubes which are 22k for EL34, 150k for 6550'
Oops, that should be 220k for EL34, 150k for 6550, sorry.
But still, there's no benefit from messing with them, they don't affect the bias, they just feed it to the grids. As the grids don't draw any bias current, there's no V dc across the grid feed resistors.
It seems that your bias supply voltage is too high, so change the resistor that feeds the bias pot, R27 currently 15k, to 22k. That should bring the bias voltage down a bit and so allow the tubes to pass more current.
http://www.schematicheaven.com/marsh...l_50w_2204.pdf
Adjust the pot to it's max value before you power up with tubes in. Peter.
Oops, that should be 220k for EL34, 150k for 6550, sorry.
But still, there's no benefit from messing with them, they don't affect the bias, they just feed it to the grids. As the grids don't draw any bias current, there's no V dc across the grid feed resistors.
It seems that your bias supply voltage is too high, so change the resistor that feeds the bias pot, R27 currently 15k, to 22k. That should bring the bias voltage down a bit and so allow the tubes to pass more current.
http://www.schematicheaven.com/marsh...l_50w_2204.pdf
Adjust the pot to it's max value before you power up with tubes in. Peter.
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