I have an older circa 1987 or 88 instrument it has been my "work guitar" since I got it.It has been very faithful until about six month ago. It has begun to fade out while I'm playing, I get about 6mins into a set and have to turn up and up till I've got to switch to another guitar. I have others but I would like to have my Washburn back! I've changed batteries till blue in the face doesn't help. I'd change the pre amp but can't find an appropriate replacement. EQ 300. Anyone have a suggestion? Is there some where I can purchase one?