Today's Mystery Guest (RCA CTC-4)

[Username1]

Well if the diode was open, then removing the new one from the circuit
should produce the symptoms it had before...... There are other
components that most likely would have passed what you were seeing....
Try removing it, see what you get....? Whaddya got to loose....?
It must have worked a little.....
Scope it with some high frequency waves, see if it waffles at some point....

.

[old_coot88]

If t'were me (which it ain't), I would go ahead and get some good red purity on it, set the grey scale, and see what a regular vid with known color content actually looks like.
Then if need be, try some eyeball tweeking of a few of those adjustments (with the exception of the reactance adj, since color sync is already good.

Others' opinions may vary.

[Phil Nelson]

After more eyeballing and tweaking, here's some slightly improved color bars:



As usual, my camera isn't very accurate. The bar that looks white is actually quite yellow, and the dark one between green and red is a dark magenta. I see now from the leftmost bar that the should-be white background was actually a little green. Yes, I should go back and do purity & gray scale, and then return to this level of tweaking.

Here's what a DVD scene looks like:



Again, the real screen is warmer and less washed out than the photo. You can see from the PAUSE letters that edge convergence needs attention, too.

The color sync is still not as robust as it should be. If you fine-tune a little bit off-signal, or even move the Hue control too far at the wrong time, faint rolling bars start to reappear. I'm tempted to reinstall the original L42 inductor on the oscillator. It looked scorched when I pulled it out, but it worked as well as the new ones in the breadboard circuit. That whole area needs to be neatened up, anyway.

The audio's not bad. Now that the rest is sort-of working, I can give that alignment a try. Still more stuff for the to-do list!

Phil Nelson