capacitor availability.

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phil99 Guru Joined: 11/02/2018 Location: Australia Posts: 3313	Posted: 04:34am 17 Jan 2023       The role of the 3 diodes (Z1) is o provide a temperature compensated bias voltage between the bases of Q1 and Q2. As Q1 and Q2 heat up the voltage drops across the B-E junctions fall. By clamping the diodes to the heatsink the bias voltage they produce will fall a corresponding amount. A simple resistance check won't tell you if they are good or not. If your meter has a diode check function use that to test each of the diodes. The forward voltage should be 0.54V to 0.65V on most meters.