Fender Vibrolux with a crackling sound

[Brian Lenherr]

Hey folks. I am having an issue with an amp and hoping someone can help.

I have a 1974 Vibrolux that crackles in the Vibrato channel. It doesn't do it when it's turned all the way down and when I have it cranked all the way up. It doesn't do it in the Normal channel at all - even with the volume at full blast.

I tapped on the power tubes and rectifier with a pencil and nothing made any noises. The preamp tubes are all under the little metal covers.

Is this a preamp tube issue or could it be something else?

Thanks in advance!!

[Dave Meis]

You'd have to remove the shields before tapping them.
Swap the first and second tubes (from the right, looking at the back) and see if the noise follows the tube from the vibrato channel to the normal channel. That should tell you if the tube is the problem ..

[Jack Hanson]

Have you cleaned its input jacks lately? Oxidation can cause the symptoms you describe.

[Donny Hinson]

As Dave said, try the tube swap, and also try turning the volume control quickly from stop to stop about 10-20 times. (Sometimes, a dirty pot can cause those crackling sounds.)