On which tune? I haven't proof of it, but it could also be that 3 guitars weren't EXACTLY in tune with each other.... That's how Def Leppard did it on "Bringin' on a heartbreak"..... Never heard of Skyn using effects.
Rossington is the one who used the phaser. They didn't start using the Peaveys until 75-76 (Bullets and One More era), so that's just a Phase 90 you're hearing on 'Pronounced', 'Second Helping', and 'Nuthin' Fancy'. Whether Rossington's personal Peavey had a built in phaser or not after that time, I'm not sure.
Thats a vibe pedal(as i'm sure you know)much more of the Jimi,trower thing.Thats gonna get much more wobble then that song has going on,but most drunk cats at a bar won't tell anyway Exactly why I use a phaser for vibe stuff.It's close & most don't need it to be dead-on.
But if your the guy that does the Mojo is the ****
I've always found the best way to get a vibe-ish phaser sound was the old MXR phase 45. I have an old DOD copy of that pedal for sale if you are interested. Great sound in a very good condition vintage box.....PM me regarding it.
tis actually a good pedal. Ive got it here sittin between my acoustic and 4 track playin some I am the Walrus and damn it makes it sound nice. Not too psychedelic, but enough. Have it sitting 1/3 of the rate up. Turned the rate up, and it pulsates in a very chorus-y, vibe-y way.