so i have an older roland jazz chorus (jc-77) some times when its on there is this sound like wind comming from the speaker, not a hum or anything, but if i hit the top of the amp it goes away. I was wondering if this was a common problem on older amps? Or if anyone knows what it is, i think its a grounding problem, but i could be wrong seeing how im not some tech genius. And lastly if it is some problem with the wiring, how much would it cost to fix it?
My old solid-state Marshall started doing this a few months ago and my tech calls the problem, "surf's up" cuz it sounds similar to waves crashing on the beach. He told me that this was usually caused by bad output transformers so it sounds like you might have to take your JC 77 in for service.

The whole job cost me $75 for all parts and labor.
Epiphone Les Paul Standard Plus '02
Fender Highway One Stratocaster
Roland Jazz Chorus 120
Marshall 5210 Combo Amp
Fender Silverface Champ
$75 doesnt seem too bad to get the problem fixed, ill have to look in to getting that fixed