howdy and welcome (back)!
i've had mine for about 5 years, sister guitar to yours, '81, ebony, original frets, series 1 with 12 in radius.
i like it more every time i play it, very unique sound with those p'ups and lots of tonal options.
you'll note the treble roll off is disabled when you select the lead pickup.
also with the the phase switch on, it doesn't matter which p'up is selected, all positions sound same
enjoy!