I have two identical Marshall DSL 100 watt heads. One of them was starting to crackle when I turned up volume on either clean or distortion channels. It  finally quit and assumed it was just dust in pod. However  a week ago turned amp head on and neither green light for clean channel or red light for distortion channel were coming on and no sound at all from either channel coming coming through speaker cabinet. Trying to get some help on what could possibly be wrong causing me to lose sound from amp head. Thanks