After enjoying this amp for a few days I decided to install the C4S board. A side works fine. Nothing on the B side. OA voltage 74: OB voltage -1.1. Both 10 and 20, 415v. The right hand LED on the B side does not light up. The other three are bright. After a day of checking everything touching up everything on the B side without success, Im not sure where to go from here. Is it possible the LED is no good. It seems like it has a very, very faint red glow towards the bottom of the LED, but I'm not sure.