The closest we got to original NBC broadcasts were the VHS/Laserdisc releases.
Yes, though I can't help the feeling that for the later video releases they fixed some things the original producers might have approved.
After GoodKirk has beamed back aboard in "The Enemy Within" Scotty feels compelled to accompany the captain some way. They stop and their dialog is almost inaudible because of an intercom announcement regarding "communication lines" (English mono B track Japanese LaserDisc Version).
In the subsequent releases it's less annoying. Admittedly no longer raw and original but not necessarily a bad thing, IMHO.