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06-01-2023, 05:28 PM
Hi Guys
Cnamp81: Electronics uses precise terms so that circuit descriptions and essays about circuit function will be clear to all readers.
The term "ground" has a precise meaning in electronics, as it is the reference for signal and DC supply voltages. Real ground is also called "earth". There are also AC grounds which is any DC point tied to earth via a capacitor, as all DC supply nodes are.
In your amp, "making a connection", or "tie 'A' to 'B'" is not the same as "grounding" UNLESS one of the related tie points truly is circuit ground.
Your description of how you connected the MV states that the MV pot-0 (pot-zero) is tied to the bias-pot wiper AND to circuit ground. This means the bias pot cannot do anything.
Look at the original PDF and see that the grid-leaks R2,4 can be replaced by the sections of a dual-pot. Pot-0 is NOT tied to ground directly, although the bias pot wiper can make that connection at the extreme of the pot sweep. The bias pot can do what it is supposed to do.
So, remove the link between ground and the MV pot-0 IF you are trying to follow the original PDF.
You can only ground the MV if it is capacitvely isolated from the entire circuit of the PDF.
Regarding the red-plated tube: It may be toast. You can check it in the circuit if you use a higher value Rk just to control it.
Really, the amp needs higher-value screen resistors if there are any, and add some if there are not.
Cnamp81: Electronics uses precise terms so that circuit descriptions and essays about circuit function will be clear to all readers.
The term "ground" has a precise meaning in electronics, as it is the reference for signal and DC supply voltages. Real ground is also called "earth". There are also AC grounds which is any DC point tied to earth via a capacitor, as all DC supply nodes are.
In your amp, "making a connection", or "tie 'A' to 'B'" is not the same as "grounding" UNLESS one of the related tie points truly is circuit ground.
Your description of how you connected the MV states that the MV pot-0 (pot-zero) is tied to the bias-pot wiper AND to circuit ground. This means the bias pot cannot do anything.
Look at the original PDF and see that the grid-leaks R2,4 can be replaced by the sections of a dual-pot. Pot-0 is NOT tied to ground directly, although the bias pot wiper can make that connection at the extreme of the pot sweep. The bias pot can do what it is supposed to do.
So, remove the link between ground and the MV pot-0 IF you are trying to follow the original PDF.
You can only ground the MV if it is capacitvely isolated from the entire circuit of the PDF.
Regarding the red-plated tube: It may be toast. You can check it in the circuit if you use a higher value Rk just to control it.
Really, the amp needs higher-value screen resistors if there are any, and add some if there are not.
