One of my power valves is redplating, and prior to that there was a really loud sound coming through the sneaker that sounded like an electrical surge. Is it just a new valve required or something else. At first there was a noticable hum,  then I went to plug in my guitar and as soon as I picked up the cable, it made that loud bzzzzzt sound and I shut it off. I then tried it again and noticed the redplating.