I looked around for a clear answer on this and didn't come across one. Maybe one doesn't exist... I did find a reference to no plate voltage would damage a tube in attempted operation, and that dropping plate below bias (in a tetrode) voltage would likely cause damage as well, but I haven't found anything stating "low plate voltage will cause damage" across the board. To define my question - If I run a tube that, for all reference's Ive found, seems to be in the 3500-4200v plate v range at 1500v - will I damage it? Before anyone brings up grid and plate current - lets assume they are held to safe levels.