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Old 24th Jul 2012, 9:12 pm   #6
Hybrid tellies
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Join Date: Jan 2004
Location: Bristol, UK
Posts: 2,456
Default Re: Binatone Mustang

Think I am getting closer to the distortion problem. I have already checked the mid point and idle current, which both are ok. They were varing considerably but I traced this to an intermittent open circuit 220 ohme resistor across one of the bias or steering diodes. Just by chance I heard a strange form of interference from another nearby AM radio when this Binatone Mustang was switched on and tuned into a station and you could vary the level of the interference with the volume control. It is like the peaks of the audio from the Binatone was radiating right across the AM bands. As I have no circuit diagram a visual inspection shows no main decoupling cap fitted across the supply line and also no capaciter on the output stage to prevent this form of oscillation. I think the only thing I can do is experiment and try different values of capacitor until I clear or reduce the oscillation and level of distortion.
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