Tomcomm,
I did spend some time on the bench running the set from a video amplifier feeding the grid of the 1st video amp. This produced a superb picture, with no noise or hash. I resorted to this because the front end of the set was performing terribly, with all kinds of noise and interference. I eventually figured out the poor front end performance was due to 1. a bad antenna balun, and 2. a crappy el-cheapo RF modulator. Once I found and replaced these two miscreants, the performance was better than I expected. So to make my life easier, I am not going to install a baseband video input and amplifier. It is good enough.
By the way, the CBS 205 design was most likely licensed from RCA, at least in part, as the IF/video/chroma/matrix sections are virtually identical to the RCA cT100. CBS designed their own tuner, defelction, HV and LV power supply, and convergence circuitry. But the color bandwidth is full I&Q. :-)
Here is a photo I took while the set was on the bench and driven at baseband at the 1st video amplifier grid. The exposure on the photo is not very good and I had not optimized the convergence but you get the idea.
__________________
John Folsom
|