K5881 one valve running cool.

[shadders44david]

Hi there, I have yet another problem with my aged K5881 mk2 and wonder if someone can help. The right channel is slightly lower output than the left and the bass notes distort at anything slightly above normal listening levels, the left channel is fine. Also, valve number 4 - far right, does not get anywhere near as hot as the other 3. I have tried swapping the valves, checking the heater circuits, changed the cathode resistor bypass cap`s (again), checked all resistor values, swapped C3 and C7 with the left channel and checked and rechecked continuity of all solder joints all to no avail. Has anyone come across this fault before ? Best regards, David.