[MrFixr55]

Hi Ferran,

Note that the volume control is supposed to be only 550 Ohm. I don't know how many watts the volume control should be able to handle, but the more, the better. The control is part of a "voltage divider". The total resistance of this string is is about 30,000 Ohm. The percentage of this string that is the resistance of the volume control is only 1.8% of the total resistance and 1.8% of the approximately 250V across this voltage divider. The voltages on the tube are very small, being 16V for the plate, 8V for the grid and 4V for the Cathode. However, these readings were made with a 1000 Ohm / Volt meter instead of one of the modern supersensitive DVMs.

The point here is any change in resistance as these resistors and the 80,000 plate load resistor heat up will possibly cause the issue that you are having. In other words, consider changing all of the "bleeder resistors", the volume control and the 800,000 Plate Load Resistor for the Control Tube. In addition, change all of the capacitors in the radio.

Good luck, I hope that this helps.

Best Regards,

John "MrFixr55"