You can test the PSG sound channels by typing simple SOUND commands in BASIC. You should hear a 440Hz sound for 10 seconds at full volume for each of these commands:
SOUND 1,440142,1000,15 should produce sound in the left speaker. (channel A) SOUND 2,440142,1000,15 should produce sound in both speakers. (channel B) SOUND 4,440142,1000,15 should produce sound in the right speaker. (channel C)
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