2A3 Single Amp broke!

2A3 single stereo amplifier is out of order now, right channel does not exert signal, 5Z3 rectifier, 12AU7 SRPP and self bias simple circuitry probably makes it possible for me to find out some defect anywhere. Long period of time interval makes me difficult to remember the circuitry and the actual way to find the error, but I will do that, though there are some feeling of tiredness. This low-frequency amplifier was assembled by myself 20 years ago, I was familiar with this kind of hobby and was skillful in this field at that time. There must something new by remembering old good days. "Know the new expressions asking the old." I prefer Triode power tube to Pentode, because of the critical reason, Second harmonic distortion that a triode has, on the other hand the Third one. The latter one causes ear drum fatigue after some long listening period of time. Not because of loudness but because of the innate Third distortion.