Please check carefully (with a magnifier) that C434 and C430 and the 3 resistors between them are in place on your QMX+ board, and that they are soldered well.? Also check the nearby IC404 to make sure all of its pins are clear and soldered well.? These are all surface-mount, and shouldn't have any issue - but sometimes a little solder flake or ball can migrate and short things out.
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There is a known issue with a DC 'thunk' happening, which can be solved by placing a 33uF capacitor across C430.? But I don't think anyone would call that 'thunk' "super-loud".? So I'm wondering if your problem is a missing C430 or C434, or perhaps R424.? Any of those could cause a big DC 'step' to appear on your speaker leads when the PA is turned on/off for each dit/dah.
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Stan KC7XE.
