Can we discuss DC restoration circuits?

[ChrisW6ATV]

Originally Posted by miniman82

As I understand it, during bright scenes any black (or otherwise dark) objects will become lighter. It's really obvious if you're watching something in letterbox format, because the black boxes at the top and bottom of the screen will get 'lighter' as opposed to staying black like they should. Really ought to be called black level restoration instead of DC restoration, that would make more practical sense.

Your description is correct for the problem. This video parameter has been called black-level retention as well as DC restoration.

Ctc17 may have a good point about CRTs, but maybe related to brightness/contrast or setup adjustments in general, and this could help explain some of our similar models with and without decent restoration. I am going to try my CTC-16X chassis on my test jig and see if I can affect it by trying different settings of the CRT bias switch among others. Years ago, I had a Sears portable color TV with lousy black-level retention, but I could make it pretty good if I cranked the contrast way down. (I had to have the room lights off and it was essentially unwatchable, it was so dim, but it really did keep its black level consistent within that low range of contrast.)