I have a Hot Tubes and an English Muff’n. The Muff’n doesn’t light up at all but the HT does. As far as I know the LED are purely for effect and have no impact on the tubes. The tubes should actually glow themselves! Usually you can tell when a tube is out by a few simple tests (google it!). What issues are you having with the pedal? If it was the tubes the pedal would probably work but just sound like crap. If the pedal won’t power on or make any sound then it could be something else.