blues_addict wrote:
So I wonder if this issue was caused by the lack of stanby switch... ???
IF (if!) there is such a thing as a negative effect of solid state rectification in combination with lack of standby switch, THEN the effect would only affect the tubes (quite possibly output tubes more than preamp tubes). If you want any hope of an answer to your question, the first thing you need to do is roll tubes. If you want the amp to work properly again, this also starts with checking the valves. Don't need a tech, just roll, play and listen.
Btw this is better off in a thread on its own, has got nothing to do with OPs intent.