Hello everyone,
I am working on a nice Adcom GFA 5800 amp. The problem I am having is that when setting the bias as per service manual instructions, the left side .5 amp regulator fuse blows hard (bright light/vaporized metal) only after about 30 minutes of running. I have amp multimeters on both regulated rails feeding the amp board also and the current is steady at 50 ma on each until the fuse blows. The fuse seems to blow when the bias current approaches about 700ma. The current on my variac, idle current, and regulated current do not rise abnormal compared to the right side until the fuse blows, then idle current goes down a bit and fan goes off. I have a thermal camera and the amp is not overheating, and the overall channel and individual components are within a couple of degrees of each other on the regulator board and amp boards. Since everything runs fine until the fuse blows I’m not seeing any odd voltages. This is a fet based amp. My question is what parts have this type of failure mode? Any clues would be much appreciated!
I am working on a nice Adcom GFA 5800 amp. The problem I am having is that when setting the bias as per service manual instructions, the left side .5 amp regulator fuse blows hard (bright light/vaporized metal) only after about 30 minutes of running. I have amp multimeters on both regulated rails feeding the amp board also and the current is steady at 50 ma on each until the fuse blows. The fuse seems to blow when the bias current approaches about 700ma. The current on my variac, idle current, and regulated current do not rise abnormal compared to the right side until the fuse blows, then idle current goes down a bit and fan goes off. I have a thermal camera and the amp is not overheating, and the overall channel and individual components are within a couple of degrees of each other on the regulator board and amp boards. Since everything runs fine until the fuse blows I’m not seeing any odd voltages. This is a fet based amp. My question is what parts have this type of failure mode? Any clues would be much appreciated!
Last edited: