Fender Blues Deluxe crackling.

[RWoody]

I have an old Fender Blues Deluxe that has a problem with crackling. It does it only when I play an A note, G note, and any chords involving similar sounds. I checked the tubes and had a microphonic v1 tube and replaced it. All the other tubes are perfectly fine. I checked out the board for any bad connections and couldn't find anything. I even completely cleaned the thing and still have the problem. Also, the crackling seems to happen only between the volume levels of 3 and 7 or 8. Any suggestions?

[Enzo]

Yes, ball up your fist and whack the top of the amp. Turn the reverb off first. Does that make it crackle? You note and volume conditions sound to me like resonant vibration in the chassis and cab. The vibration causes some loose connection to open momentarily.

Apply a steady signal to it, and while listening, push on each part on the circuit board with someting insulated, like a chopstick. Any part that affects the sound or makes noise is loose or otherwise involved.

[RWoody]

Whacking the top of the amp causes no crackling at all.

[Enzo]

Then head through it part by part looking for anything that responds to mechanical input.

While playing it to crackle, have someone grasp each tube one at a time and hold it firmly. Use a rag or a glove if they are too hot. Does holding onto any tube have an effect?

Pay attention to wires to the sockets, wiggle each, any result? looking for solder issues.

Does it still do it with the chassis out of the amp and sitting on the bench plugged into a speaker elsewhere? That determines if it is vibration related or electrical. If it stil does it, then something is breaking down under voltage. At that point we get out the scope and start looking.