[old_tv_nut]

By the way, ALL sets, even those that do not have luma DC restoration, must have DC coupling or restoration in the chroma. Otherwise, the gray scale tracking drifts depending on scene color content. RCA put DC restoration in their X-Z demod matrix circuit, although books don't explain it. The blanking pulse on the R-Y, G-Y, B-Y matrix amplifier sections causes them to draw grid current [edit - in the amplifer triode, not the CRT], which makes the grid/cathode into a DC restorer diode.