Zenith 25EC58 Restoration Thread

[TinCanAlley]

Originally Posted by vol.2

Yeah, it's extremely tricky.

I still think that it's probably a case that the set always had those bars, but there was something acting as a low pass filter which provided some kind of anti-aliasing just as a side-effect of the component tolerances at the time.

Or it's a shielding problem or a grounding problem.

I think I'm finally going to find out if it's an IF issue. I watched a video on someone taking a portable set from '76 and connecting composite directly. He had to short a resistor in the IF section, but I won't need to do that as the entire IF module comes out on mine. Also, the point where he inserted the composite he use a 75ohm resistor and a 47uf capacitor. I am going to modify an old 75ohm RCA by cutting off the head and attaching the resistor and capacitor and terminating it with a barrel connector big enough to fit over the C1 test point to insert directly into the video amp like the IF does. If it works, I'll not only have the video image, but I'll be able to see if the bars go are gone or not. Even if they are still there, I'm going to create a way to leave the IF in and switch from RF to Composite as needed.