Can we discuss DC restoration circuits?

[freakaftr8]

Ok, good topic. As Chris had mentioned, I have seen good DC restoration on a CTC-16, modt likely the one Chris had mentioned in his thread. I have a CTC-17 (Zenith CRT)with decent DC restoration and my other CTC-17 (RCA CRT) with non existant DC restoration. The first chassis I believe is an XAB and the other chassis is an XAD IIRC. Im curious as to what causes this as well. Were there modifications done at the factory, or was this pissibly a field service call somewhere later. There has been to circuit modifications I can see to the XAD chassis at all. I have two 23" Zenith consoles from 1967. One has decent DC restoration, and one has none. I dont recall the chassis numbers off hand, but the one with decent DC is an SC600.