Add a 1000uF (or higher) capacitor across the V+ rail to ground.
Look up the spec sheet
Different manufacturers might have minor differences.
The zobel network, low value capacitor in series with a low value resistor is critical and the specified values might not be correct depending on layout.
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Sometimes you need a 1uF cap directly across the IC V+ to ground, on the pins.
Sometimes the minimum gain of 20 is too much and you need a resistor across AF +/- in directly across the pins. 10K worked for me.
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Could the original electrolytics have dried out? Rat Shack wasn't known for milspec quality.
