Which ones are you using right now? I bought some at my local radio shack for a couple of bucks each. They sell red, green and amber ones in 3 or 5 mm sizes ( I used the 3mm ones). Something like this one;
http://www.radioshack.com/product/in...ductId=2062548 They have other styles. If you want a blue one, you have to use another vender (I bought mine through DSE). I wonder how they are "blowing", is all of the wiring good?