Bought my first SVT-CL about 4 months ago used and in great looking condition. I was told it has hardly used and it looked it. Serial puts it made in 98. All the LEDs worked for the two rear user biasing controls and they all read correct biasing. Tonight I noticed that the green LED on the right side has burned out or just does not work. Also, the biasing balance on the half burnt pair seemed to be off a tad. Do these LEDs burn out frequently? Is this a common prob and is this a normal amp tech repair?