Last week the standby switch stopped working, checked the switch its fine

I’m not getting any voltage to the tubes and I have checked the circuit resisters etc and everything seems fine. It’s got new filter caps that are properly installed. I was thinking maybe problems with the Transformer but if I fire up the amp with the on switch (I know it’s hard on the tubes) everything works fine and my voltages AC,DC and Bias are all fine. I was hoping someone could shed a little light on the matter. Thanks JGK