WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
Building, troubleshooting and testing of these amplifiers should only be
performed by someone who is thoroughly familiar with
the safety precautions around high voltages.
Then, the best thing I have to do is to check each resistor, and to change only the bad with carbon. It's only in the HT line of the IF section, I'm too afraid to touch anything in the RF !!