[johnny diesel]

Picked up a Jr. rather cheap with the intention of running it through a 2x10 vox cab. Surpirse!! The strong ringing noise isn't limited to the Weber 10F100 speaker in the Jr - when I plug it into another cab, the noise carries on.
I know there are countles threads on how to achieve the ultimate Jr. tone. I just want to get a noise-free sound of this litle demon.

What's the quick fix?
Thanks
johnnie