In Reply to: Re: Motorola vs Mospec posted by billwjr on September 6, 2006 at 15:14:22:
once you get your transistors replaced, check the voltage across the emitter resistors. it works well if you have .47 ohm emitter resistors, you multiply the voltage by 2 to get the idle current (I=E/R). your idle current should be about 20ma. if somebody tweaked it for "class A" (actually high idle current class AB) operation, you may find your idle current as high as an amp or 2. once you get your idle current set properly, you can fine tune it (if you have a noninductive dummy load and a distortion analyzer) run the amp to full power at 2khz and check the crossover distortion (distortion spikes on the o-scope output of the distortion analyzer that appear where the signal crosses the zero line) and fine adjust the idle current until the spikes just barely disappear.
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- Re: Motorola vs Mospec - unclejed613 17:05:47 10/26/06 (0)