The reason a fuse blows is due to some semi-conductor device now acting like it was a piece of wire. The thing could be either in the power supply part or the main amp device. If you see something like a transistor or IC that's been getting hot or is damaged that will be the culprit. If all OK, If I was you, I would replace first the main part for the amp section. It might be the biggest or on a heatsink.
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The reason a fuse blows is due to some semi-conductor device now acting like it was a piece of wire. The thing could be either in the power supply part or the main amp device. If you see something like a transistor or IC that's been getting hot or is damaged that will be the culprit. If all OK, If I was you, I would replace first the main part for the amp section. It might be the biggest or on a heatsink.