How important is this cap's value (Sony 8-301W)?

[Phil Nelson]

I could be nuts, but the Sams manual calls X5 the "AGC amp" and it seems to take input from the 4th video IF as well as from the manual gain control. I am not good at puzzling out solid-state stuff. In any case, it behaves a lot like my RCA 630TS, whose manual gain was called the Picture control. A better label might have been the Twitchy control .

Having full gain from the antenna at all times seems good for my setup, where the old TVs primarily receive signals from the in-house modulator.

The hum definitely sounds like 60hz. Trying a 12vdc supply should be easy enough. I haven't examined anything in the power supply yet, since it plays plenty bright and plenty loud. A p-s can have noise interference even if it supplies adequate voltage, though.

Phil Nelson

[Mr Hoover]

Hi
I never really paid much attention to that part of the circuit as no problem with it..It's a very poor AGC system for sure...Make sure C19,30uF in the AGC circuit is ok or you might end up with some video modulation on the AGC line.

Playing with mine just now on a strong signal the video can be "moved" a lot within the screen by adjusting the normal line hold control at the rear.If it's
almost losing lock one one max setting that black curvy part as in your picture appears on the right side.Increasing the manual gain control (on a strongish signal anyway) forces the line oscillator to have a wider pull in/lock in range.

Hugh

[Phil Nelson]

It's interesting how the controls interact and how different signals affect it. Here's the same DVD machine playing different program material:



For this DVD, the gain was turned up higher than for the test pattern DVD. No gap on the right, and there's probably still some warping, but not much you would notice.

Now that it basically works, I can spend some time finding the best compromise with the various adjustments. I'm still curious about that vertical bias control, too.

I was hoping to avoid it, but I need to remove the CRT to recoat the bell with Aerodag graphite and clean the inside of the safety glass. The CRT is shedding flakes of aquadag and some of them end up inside the cover. If you look back at the earlier photo of Hilary Swank, you'll see a big black flake that's not present in later photos. I tried blowing them out with a little rubber hose, and just created a mini blizzard of black flakes, so the old coating is not done shedding.

Phil Nelson