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.

[TinCanAlley]

Okay, so on the remote motor setup, I think I know what's what. The motor's setup is spring loaded and puts pressure on the tan gear thing. The other end side of that gear connects to a gear in the channel selector unit and that gear has metal contacts that also act as sprints pushing from the other side towards the motor. The tan gear thing doesn't actually mate up perfectly with the black one. The teeth only match up around 1/3 of the circumference. It is designed to slip over the black one when the motor turns, but stay in place all other times. With pressure from the spring on the motor side and the channel selector side, it's enough to let the tan one turn and then turn the channel selector gear. Still would like to get my hands on a replacement for possible future need.

Once I've gotten the replacement caps delivered, I'll install and reassemble. Hopefully the cleaning and reassembling will cure the channel changing issue.