According to the specs I found, that unit has:
Tube Compliment:
4 X EL34
2 X 6SN7
2 X 6922
2 X 12AT7
2 X 12AX7
It's probably not the EL34's or the 6SN7's. It's more than likely one of the 6922/12AT7/12AX7. I'm not sure how Onix uses these tubes in the circuit, so it's kind of hard to pin-point the culprit. I agree with tapping each tube with a pencil eraser lightly to see if you can find the noisy tube. Wow, that unit sure uses alot of tubes...
Tube Compliment:
4 X EL34
2 X 6SN7
2 X 6922
2 X 12AT7
2 X 12AX7
It's probably not the EL34's or the 6SN7's. It's more than likely one of the 6922/12AT7/12AX7. I'm not sure how Onix uses these tubes in the circuit, so it's kind of hard to pin-point the culprit. I agree with tapping each tube with a pencil eraser lightly to see if you can find the noisy tube. Wow, that unit sure uses alot of tubes...