Aesthetix Io won't start...

I have had no problems with my phono preamp until yesterday, and like it a lot. Yesterday it stopped working. With the Io, the normal operation is that when you turn it on (on the power supply), there is a Heater light that goes on immediately, and then a High voltage light next to it, that goes on after a few minutes. Now, however, the High voltage light stays off, and there is no sound. I have tried waiting for an hour, changing the power cable, checking the fuses, and even changing all the tubes both in the power supply and in the main unit. But it did not help. Any ideas?