DC Lowering Resistor Issue in tube amp circuit

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Iceberg321

Joined Dec 1, 2023
10
I’m making a tube amp circuit based on a known schematic, and I’m having trouble with higher DC voltage than expected after the rectifier and voltage doubler network. I’m supposed to be getting around 210 V DC, and have about 260 V DC present. I changed both of the 10 microfarad voltage doubling network caps for 2.2 microfarad and that reduced the output voltage slightly. Schematic says to reduce value of a 470K ohm 1/2 watt resistor to ground after this section if the voltage is too high, but I’m not getting any significant volt drop unless I reduce the value of that resistor to under 10K…and then it’s getting way too hot. This resistor is before a 2.2K ohm 2 watt voltage resistor that is followed by a 33 microfarad 350 V smoothing cap to ground. Which is where the 210 VDC is supposed to be. Ive added a second 2.2K ohm resistor there in series, and it didn’t effect the voltage. I’ve measured and it’s been as high as 305 VDC. I’m using a 30 microfarad 500 volt smoothing cap, because that’s what I had available, could this difference be causing this issue? The AC voltage feeding the rectifier and voltage doubling network is 100 V. Schematic is attached. Any and all suggestions or check points would be greatly appreciated, thanks!!
 

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MisterBill2

Joined Jan 23, 2018
17,800
Use the 10 MFD capacitors, and build the rest of the project. When the amplifier tube is drawing power the voltage will be less than with nothing using power. The "No LOad" voltage will always be greater than the loaded voltage.
 
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