I just got me Fender 2x10 rumble 100 watt amp and I know that usually they have the lights at the bottom. Well my amp doesn't, it has the bulbs, the switch in the back to turn the light on and off but it doesnt work. So defective amp? Or am I dooing something wrong? P.S. I realise this isn't a big deal and I don't really care about it but I'd like it to work.