u/Low_Beginning_7240

My Fender blues Jr makes a loud hum after turning on, regardless of any volume or gain settings. It starts quiet but gradually becomes louder until its extremely loud. Ive only included a 30 second clip because of the video file size but it eventually becomes super loud. I've turned all the knobs down for the purpose of showing its not any of those setrings. Im a complete novice, what could be wrong? Thanks in advance.