Once or twice we got what the japanese didn't get : the PS-X7 was export-only.
In Japan, the top end of this mid-end lineup was the PS-X6 : same everything but for the carbon-fiber tonearm !
"Mid-end", however, is used here to describe a turntable designed and made during what arguably was Sony's best period. So it may look like a flimsy piece of plastic but it really is NOT.
The only "mid-end" part of the PS-X7 is the tonearm which is unfortunately fixed and isn't the PUA-1600S found on the PS-8750...
Technically, the PS-X7 / PS-X6 is a revamped PS-4300 (march 1976) without pitch controls and a much more compact motor - compact and therefore cheaper.
The difference between the two drives is equivalent to what Pioneer did between its original SHR motor and the later versions of it : PL-50L vs. PL-50LII.
The motor of the X7 is nevertheless extremely durable.
The basic speed locking technique is equivalent to all other 1976-1981 Sony turntables : barium-ferrite magnetic imprint, 8-pole reading head, X'Tal locking by phase loop and brush-less / slot-less motor.
The rest is also equivalent : dynamically balanced diecast aluminium platter, optical end-of-disc detection and mechanism, non-resonant SBMC enclosure (Sony Bulk Mold Compound), height-adjustable gel-filled feet and, for the PS-X7, depending on markets, the same OL-2K oil-filled platter mat as sold with the earlier TTS-8000.
The PS-X7 is a stunner which sold extremely well worldwide then and still astonishes those who -thinking they only get a cool-looking piece of outdated japanese junk- buy one for 50€ and, once properly hooked up, can't believe the sonics of this cool-looking piece of... enduring japanese engineering.