I need your help with my EBS Fafner that started malfunctioning lately. It develops a noise - it sounds like a 50Hz hum. It appears regardless of the input gain or EQ controls. When I turn the amp on, it is dead quiet for 3-4 seconds and then it starts. As I turn the volume more and more, the hum gets progressively louder. I thought it was the preamp tube, so I swapped it with a new one, but it didn't help - it behaves the same. I troubleshoot everything - changed speaker cable, then power cable, but it still hums. I noticed that it almost disappears when I turn the drive all the way up. It completely disappears when the drive is fully clockwise and the "Character" switch is in inner position. I tried the trick with connecting a patch cable to effects send/return, but it didn't help. I uploaded a video on the youtube, please make sure you are watching it in Hi Quality and using the headphones so you can hear what's going on. Believe me, it is much worse in person - my camera doesn't record audio very well. There is another issue that I forgot to record: when volume is set at any level above 0 (let's say 9 o'clock) and the gain on minimum, when I play the bass, I can hear a distorted sound. It used to be dead quiet. I don't know if this is related to the first problem, but both of them started at the same time. I tried to contact EBS to give me the schematics, but they pointed me to the EBS dealer in my country. It is 500km away from me and it's really not convenient for me to ship the amp. On the other hand, I have a local tech that I really trust, who fixed a lot of stuff for me so the schematics is the only thing I need. Thank you.