I have an old 1990 JCM 900 model 4101 EL34 valves. I have owned this amp for almost 20 years. About 10 years ago it blew a tube so I put the amp in storage thinking some day I will buy new tubes and bias it. Well that day has finally come. I went to measure the plate voltage to get my bias value, Pin 3 on all the EL34's are running at 1015 volts. I also measured off the transformer and it has the same voltage. I am pretty positive it should be in the upper 400volt range. Would anyone know what would cause this?