11-30-2011, 11:19 PM
90 the 1M resistor is feed for the grid bias voltage to the 6R7. I'm thinking that you should have about -3v at it and the junction of 110. Is 90 good? Did you replace the electrolytic caps around 110 and 111.
What's happening is without 90 in place there is no bias on the grid of the 6R7, that cause the tube to draw more plate current. That causes more of a voltage drop across tube and lowers the plate voltage. With 90 in place less plate current higher voltage.
Yes you can tack in a jack at the wiper of the volume control and it will control the volume.
It's better to have more - voltage cause it will cause the tube to draw less current. That's why your plate voltage went up when you got the proper bias voltage on the 6L6's. They can haul down a lot of current like 100ma each.
The plate of the 6R7 should NOT be grounded!
Terry
What's happening is without 90 in place there is no bias on the grid of the 6R7, that cause the tube to draw more plate current. That causes more of a voltage drop across tube and lowers the plate voltage. With 90 in place less plate current higher voltage.
Yes you can tack in a jack at the wiper of the volume control and it will control the volume.
It's better to have more - voltage cause it will cause the tube to draw less current. That's why your plate voltage went up when you got the proper bias voltage on the 6L6's. They can haul down a lot of current like 100ma each.
The plate of the 6R7 should NOT be grounded!
Terry
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got it!
Terry
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