From 1990 onward, the ES decks were from one year to the other simply facelifted, slightly facelifted or very much facelifted, with little mechanical improvements to justify the new name. So: the 990 is a 970 and the 890 truly is nothing more than a 870 - both originals being from the previous year's lineup... The K990 is a japanese TC-K333ES-A, the K890 a TC-K222ES-A. Only Japan saw the real 13,6kg fully copper-plated TC-K555ESA, visually identical to the TC-K990ES. Then there was the TC-K555ESJ - ultimate model -refinement- of the "classic" ES period.

No Dolby S yet but 3 heads designs for both. Like earlier (or later) decks, these boasted huge power transformers, 70µ PCB tracks, MOS-FET transistors in the input/output stages, GIC filters, FET head amplifiers and Sony's much touted (and excellent) TCM-200 mechanism. As all early 1990s Sony units, build-quality is nowadays... completely unbelievable.

ps. I have better images in my japanese ES catalogs - stay tuned !