My MKII is starting to cut in and out.  I'll have strong volume, them in an intant it's about 1/2.  It will jump like that.  I have had this amp for almost 1 year and this started roughly 1 month ago.  I checked the tubes, they appear seated correctly.  Could I have a tube issue or is this a known issue with the amp and it's going bad?  This is especially bad due to I am in a working band that is out every weekend.  Most Line6 shops tell me 4-6 weeks, which is completely unacceptable.  Any advice/help?

Thanks