Re: Debug audio section noise

On Tue, 31 Jul 2012 22:42:46 -0700, you wrote:

>I have a babypac vidiot board which getting my hand anywhere near the volume
>pot makes it put out a big racket. Running my finger along the various caps
>/ resistors in that section also sets up a nice noise. I have another of
>the same board where the above don't cause any problem.
>
>I am a bit weak in analog so short of shotguning the various components I am
>looking for a clue on where about to start.

        Well, the first place to start is -- what *kind* of noise are you
talking about, here? Is it a 60Hz hum, or a high-frequency squeal, or
static, or... what? Is it continuous, or intermittent?

        If it's a static-y sound that mostly occurs when you touch or wiggle
the components on the board, the most obvious suspects would be a bad pot,
or cracked solder joints around the various components. If the chips are
socketed, it could also be oxidization on the chip legs.

        If it's a hum, especially a 60Hz hum, I'd put a scope on "+12V Unreg"
to see if that +12V has a lot of AC ripple on it, which would suggest a bad
diode or filter capacitor in the power supply section.

        If none of the above, then a more complete description of the type of
noise might help narrow it down a bit. :)
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Received on Thu Aug 2 23:42:47 2012