I'm trying to sell my Ampeg-SVT, love the sound but im going for a more lightweight setup. The problem is, the bias lights can only show red. The green light wont go on when the red goes of, but i remember that the green light worked (only on one of the sides though) about a month ago. I searched a bit, and if i understand it correctly, it ussually works to change some tubes. Since im selling it, i wont bother changing tubes, as long as the amp is fine, but should i be worried? Should i let a tech check it out, or should i just remind buyer that it will most likely get fixed by changing tubes? Thanks in advance, Kasper.