My preamp has a noisy ALPS volume control. The weird thing is that it is only noisy (crackly) when first powered up but after a few minutes, the noise, for the most part, goes away. I opened it up to clean it but have never seen a pot like this before.
Any suggestions would be greatly appreciated.
Any suggestions would be greatly appreciated.
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Your description indicates that on power-up some preceeding coupling capacitor builds up a dc voltage across that potentiometer -
which generally is contributing to additional noise: The more DC-voltage, the more noise.
This DC-voltage should disappear quickly after coupling cap is fully charged.
Anyway you should measure with some multimeter whether there remains some permanent DC-voltage residual across that potentiometer.
In that case the coupling cap may be leaky - or some other reason like input bias current from the ciruitry.
Replace C502, 504, 506, 508, 510 with new high quality parts, like the Nichicon UES series.
Use 25 or 35V parts.
Use 25 or 35V parts.