Have you checked all the fuses on the power supply board? I am sure that you have. F01 and F02 are the likely suspects they supply the power for the preamp section and the voltage for the tuner power supply. Check to see if you have any voltage on the two big white resistors on the tuner (left side) (should be about 36 volts). If not the problem is in the power supply I will email you the power supply section of the 9090 this weekend once I return home from my trip. PM me on Sunday as a reminder.
I am assuming that yours is a 9090 and not a 9090DB.
Good Luck,