My SP-6 has become quite noisy in the phono section. A suggestion in another thread was to clean all the tube pins and contacts. I've done this and there has been no improvement. The manual states that "if excessive noise should develop in the phono section only, it is most likely V1." This tube is easily found in the schematic supplied in the manual, but how do I identify this part in the case without the part numbers being labeled in the chassis? Then, once the correct tube IS identified, are tere any special biasing procedures required once the tube is replaced, or is it pretty much plug-n-play? The manual does not give any indication of this; it's only a user man, and not a service man. Last, I aquired this second hand a couple years ago and have listened through it extensively, so should I go ahead and re-tube the whole thing or just replace the likely culprit?