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Hi there,
I am new to this bias adjustment concept. I read a few websites and followed two pages of instructions by Reeves Amplification.
Unfortunately Bill at Reeves mentions after finding out the plate voltage (pin 3 to ground) -> 499 volt, I use the bias calc website to find out the amount let's say at 70 percent (35 mA) and measure pin 8 to ground but when I asked him the pin 8 to ground will read voltage not current, he didn't give me a clear answer.
This amp has a power scaling (PS) so at least amount it is supposedly amp bypass, and at highest amount (dialled clockwise) it is at 100 percent (no power scaling).
There is a 1 ohm resistor between pin 1 and pin 8. Yesterday I realized the voltage across the 1 ohm resistor gets to a high point around 8 or 9 o'clock (at 10 to 20 percent power scaling) but when I turn the power scaling further clockwise (less scaling and more of the real power), the voltage drops from let's say 35 or 40 toward 12, 10, 7, ... and at max PS setting (no power scaling) it actually gradually drops below 7 toward 5, etc. I was surprised. Today I realized I'm supposed to measure the current to the ground, not necessarily pin 1. Is it possible that pin 1 is not grounded, therefore the charge from the plate, cathode, etc. influences the charge on pin 1 (suppressor grid) and that causes the drop in the current between pin 1 and pin 8?
If so, in order to measure the cathode current, can I ground pin 1 with a piece of wire with alligator clips and do the measurement afterwards? I don't understand why Bill said I can just hook on the multimeter from pin 8 to the ground. How does the volt measurement from pin 8 to ground correlates with the cathode current to the ground?
Thanks for helping me out to clarify this.
Cheers,
Arya
I am new to this bias adjustment concept. I read a few websites and followed two pages of instructions by Reeves Amplification.
Unfortunately Bill at Reeves mentions after finding out the plate voltage (pin 3 to ground) -> 499 volt, I use the bias calc website to find out the amount let's say at 70 percent (35 mA) and measure pin 8 to ground but when I asked him the pin 8 to ground will read voltage not current, he didn't give me a clear answer.
This amp has a power scaling (PS) so at least amount it is supposedly amp bypass, and at highest amount (dialled clockwise) it is at 100 percent (no power scaling).
There is a 1 ohm resistor between pin 1 and pin 8. Yesterday I realized the voltage across the 1 ohm resistor gets to a high point around 8 or 9 o'clock (at 10 to 20 percent power scaling) but when I turn the power scaling further clockwise (less scaling and more of the real power), the voltage drops from let's say 35 or 40 toward 12, 10, 7, ... and at max PS setting (no power scaling) it actually gradually drops below 7 toward 5, etc. I was surprised. Today I realized I'm supposed to measure the current to the ground, not necessarily pin 1. Is it possible that pin 1 is not grounded, therefore the charge from the plate, cathode, etc. influences the charge on pin 1 (suppressor grid) and that causes the drop in the current between pin 1 and pin 8?
If so, in order to measure the cathode current, can I ground pin 1 with a piece of wire with alligator clips and do the measurement afterwards? I don't understand why Bill said I can just hook on the multimeter from pin 8 to the ground. How does the volt measurement from pin 8 to ground correlates with the cathode current to the ground?
Thanks for helping me out to clarify this.
Cheers,
Arya
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