Started a few years ago and I tried everything. Dozen cables, dozen guitars, active/passive pickups, dozen power cables, dedicated power from the fuze box, on a UPS battery backup for clean power, nothing helps.
On all modes/settings/effects combinations, my amp will randomly have what I can only describe as an extremely slow phaser effect? It slowly loses all low/mids and then gets all screechy/hissy/whiney. Suddenly like as if you popped your ears and they stop ringing it goes back to normal.
I looked at all of the boards, all caps and connections look good. At this point do I scrap it and buy another amp? Boards for these things aren't cheap and aren't guaranteed to not have issues in the future.
