• 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.

Help! circuit diagram

My old man gave me a stereo amplifier[mono bridge-able] "goldentube 300Bse , commercial product, it still can't sing on right channal. I try to find a circuit diagram like an original design[6SL7>EL34>300B, 5AR4 as rectifier] to fix it.
Can anyone help or provide circuit / link? please. I'm new diy babie.