I've seen more than one ARC power amps like the VT100 series advertised on Audiogon with black char marks where a segment of PCB copper trace caught fire and evaporated. The common fix is to clean each end of the open copper trace and solder a jumper wire across the gap. In one ad the owner rated the amp as 9/10 excellent condition when you can plainly see the repair in the posted photos. I suspect the owner may have bought it used and had no clue.
