Line 6 experts.....

[FRANKJC]

My son's line6 spider 120 makes a bunch of crackly noise when playing. He showed me that if you give it a slap on the top near the handle, it goes away.  I played it today for a couple hours, and it's a pretty good sounding amp. It would be a lot more useful without all that noise. Any ideas? Thanks.

[Enzo]

Something is loose.  I start by making sure all the nuts on controls and jacks are snug.   For that matter any screws that anchor circuit boards and transformers.  Loose hardware can indeed make electrical noises.

Use a wooden chopstick or something insulated, and poke at the components to see if any respond with noise.

Cracked solder most anywhere could also be the cause.

[FRANKJC]

Thanks i will try that. It would not surprise me if something were loose, this amp has a lot of road wear on it, my son's buddy gigged a bunch with it.