Shearne Audio Amplifier Repairs

John Shearne Phase 3 Stereo Power Amplifier

This had blown the mains 2A fuse. Investigating the internals unearthed the Darlington power transistors being short circuit. The small driver transistors on one channel had burn marks under them and had been replaced earlier in their life as had the Zeners. This was a design by the late Tim de Paravicini who, I was informed, had done the previous repair. The power transistors looked as if they had been cooking for a while so I took a simple step to reduce this by removing the plastic coating behind the aluminium bracket to allow for better heat transfer.