Zenith 25EC58 Restoration Thread - Page 7 - Videokarma.org TV - Video

TinCanAlley · #91 04-19-2026, 06:51 PM

I haven't removed the remote motor yet as I'm still trying to figure out if I remove it, will it go back in smoothly. It has a strange toothed base that seems to be misaligned as the teeth mesh perfectly on the top, but seem to be off on the bottom. I can also see the particles from the tan part all over as it sheds/scrapes off. There is also a set of teeth on the base of the motor shaft that turns another gear next to it and a leaf switch. I know I need to find out what is wrong as half the time when I change the channel, it either gets stuck and I have to go back and forth to make it move, or it moves but takes a second or two to finish the rotation.

I'm attaching a couple pics in case someone has seen this setup before and can give some insight on what might be going wrong.

TinCanAlley · #92 04-20-2026, 12:00 PM

So who can tell me how this works?

I took apart the motor assembly to see why it sometimes doesn't change or seems to get stuck. The design seems to stump my brain, so I'm hoping someone here knows how and why it works. What really sucks is the one most important gear still seems functional, but I don't know how well it will last, if not forever. It is an odd design. The shaft is hard plastic, but the gear platter and teeth are flexible (to a point) and the back side is on the soft/grip side.

This is how it is configured. I've attached a couple pics. The motor shaft has a spring loaded black piece that has teeth up on the shaft that turns a gear and cam that activate leaf switches. I'm assuming this is how it knows it has gone the right amount to change one channel. Then the bottom of the black piece widens out and has two protrusions on the bottom that sit against the tan gear looking thing. That tan one is meshed with the black one on the bracket. The black one does not turn at all. It is keyed and sits in the bracket. So somehow, the motor turns and the black piece on the shaft turns on the tan one and gets it to turn, even though its teeth are meshed with the black one. Turning the black one by hand just makes it spin on the tan one, not make it move. So it can't be added pressure that makes it turn as that would force the teeth together tighter and never turn. Makes my head hurt.

Also, the tan gear has no part number and neither does the black piece over the motor shaft. The black on in the bracket does and I found one on ebay. Don't need it, but just curious if they exist. It would seem the tan one is a wear piece, so why no part number? Hmmm....

vol.2 · #93 04-20-2026, 12:08 PM

Quote:

Originally Posted by TinCanAlley

I'm starting to think the jailbars are coming from some other source (IF?).

Random jailbars in the raster is one of the very most difficult things to figure out.

From what I've been able to gather in my quest to solve jailbar problems in my own sets is the following:

1. They can be caused by missing shielding. Sometimes there were big metal shields covering things like the flyback or other noisy sections of the chassis, and they go missing during the life of the set
2. Sometimes grounding problems can cause them. This can also be caused by a missing ground that was completed by a shield or a poor connection on the tube itself or elsewhere.
3. In many cases, the jailbars were always there, and the reason you are seeing them is because newer components are somehow accentuating their visibility. I have been told by people more experienced than me that this can be due to fast, better performing parts passing through more of the bars. I would assume that this is a frequency related effect where the edges of the bars would have originally been smeared together more, and now your fancy new parts are allowing more high frequency information through and it's simply showing the edges of the bars that always there more clearly.

In the last case, my approach has been to look for a place that changing a value could potentially reduce that a little bit. Basically to create a low-pass filter in the exact spot where the jailbars are being introduced.

I haven't had a lot of success with it yet though, so YMMV. I know just enough here to understand people's suggestions, but I don't have a strong enough background in electronics to do much innovating.

TinCanAlley · #94 04-20-2026, 12:51 PM

Quote:

Originally Posted by vol.2

Random jailbars in the raster is one of the very most difficult things to figure out.

From what I've been able to gather in my quest to solve jailbar problems in my own sets is the following:

1. They can be caused by missing shielding. Sometimes there were big metal shields covering things like the flyback or other noisy sections of the chassis, and they go missing during the life of the set
2. Sometimes grounding problems can cause them. This can also be caused by a missing ground that was completed by a shield or a poor connection on the tube itself or elsewhere.
3. In many cases, the jailbars were always there, and the reason you are seeing them is because newer components are somehow accentuating their visibility. I have been told by people more experienced than me that this can be due to fast, better performing parts passing through more of the bars. I would assume that this is a frequency related effect where the edges of the bars would have originally been smeared together more, and now your fancy new parts are allowing more high frequency information through and it's simply showing the edges of the bars that always there more clearly.

In the last case, my approach has been to look for a place that changing a value could potentially reduce that a little bit. Basically to create a low-pass filter in the exact spot where the jailbars are being introduced.

I haven't had a lot of success with it yet though, so YMMV. I know just enough here to understand people's suggestions, but I don't have a strong enough background in electronics to do much innovating.

I don't know if my way of thinking about it is correct, but I feel that if none of the changes have even affected the bars, it must be somewhere else. I've changed every diode, the related ceramic capacitors and resistors. I changed the damper diode. Rerouted harnesses. Cleaned contacts. Checked all ground points on terminal strips. Replaced every electrolytic with part numbers from SM. Checked IF cables for damage and proper grounding. Not once have I seen any change in the jailbars. The only sections I haven't dealt with is the flyback, IF and yoke. The only missing shield is from the subcarrier module and that's due to the new module not needing it as it has its own shielding.

I found an NOS IF module that is bright and shiny and the box doesn't say "remanufactured" on it. The only thing I don't know is if the module comes pre-aligned. If not, then I'm short on equipment to do so. I also found an NOS flyback. I can easily test the IF module, but the flyback isn't plug and play.

I am dedicated to getting this TV back to as new a condition as I can and have been happy with all the work I've done that has increased the image quality and audio, but the jailbars are way too noticeable. They cover the entire screen, albeit less as they go from left to right, but they're still there.

old_tv_nut · #95 04-20-2026, 02:15 PM

I think the new IF module would be prealigned. Stop agonizing and just try it.

It's not likely it would affect the jailbars, but who knows? Replacing it might fix a ground problem.

vol.2 · #96 04-20-2026, 02:19 PM

Quote:

Originally Posted by TinCanAlley

I don't know if my way of thinking about it is correct, but I feel that if none of the changes have even affected the bars, it must be somewhere else.

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.

TinCanAlley · #97 04-20-2026, 05:36 PM

Quote:

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 · #98 04-20-2026, 05:42 PM

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.

TinCanAlley · #99 04-20-2026, 05:43 PM

Quote:

Originally Posted by old_tv_nut

I think the new IF module would be prealigned. Stop agonizing and just try it.

It's not likely it would affect the jailbars, but who knows? Replacing it might fix a ground problem.

IF module arrives today. Will have to wait til I get the caps replaced in the tuner control center board and put the unit back in the set. I'll swap the IF module after I verify I got everything back and working.

TinCanAlley · #**100** 04-21-2026, 05:06 PM

I got the NOS flyback, but I'm questioning the instructions with it. I am not planning on installing it and if I do, it's only as a last resort. The one installed in the set is S96453-01. The replacement is -02. The sheet sent with it says that if replacing a -01, I need to remove the .0006 2KV ceramic before installing. I've compared each unit and other than the new one having the safety caps already updated, and a single resistor replacing 2 in parallel on the current one, I see no real difference. If the current one has the 2KV, and all other components on the new one are the same connections and values, why remove the capacitor?

Thing is, if it does need removal, then I have one to test in the circuits that use this capacitor (damper, boost, etc.). Haven't been able to find this value in 2KV.

TinCanAlley · #**101** 04-23-2026, 04:40 PM

While removing capacitors from tuner control board, the solder sucker not only took the solder, but the pad as well. These are the worst pads I've seen. Since I have no idea how to restore the pad, if even possible, I am thinking of soldering the lead to the next joint on the trace. Just want to make sure this is okay before I do it. Pic attached.

Also, removing the board meant two gears falling out. I figured out their alignment, but hope it all goes well as the only way to know is reinstalling for testing. Wonder why this part of the tuner isn't in the Sams supplemental along with the remote board that is part of this assembly.

TinCanAlley · #**102** 04-23-2026, 04:55 PM

I retested the CRT with a BK 470. It passed all tests. When setting the cut-off, all three guns were close in knob position to set it. The emissions test showed the green gun lower than the red and blue, but not by much. The instructions don't say anything more than the CRT is considered good as long as each gun is in the "Good" section. The scale goes up to 20 and the red and blue were 13, while the green was 12.5. I'm assuming those are good reading for a 52 yr old tube and it has many hours left. Each gun passed tracking as well.

BeamT · #**103** 04-23-2026, 09:06 PM

Hopping over the adjacent trace would be acceptable in this application. I would suggest using a short piece of spaghetti tubing to insulate the lead over the hop. You might also consider potting the electrolytic in a very small amount of adhesive to give it some mechanical stability. You could also gently scrape off the enamel on a small area at the end of the remaining trace to create a new pad. Form the lead to recreate the path of the missing trace, and solder to the pad you created. Consider potting the lead in a very small amount of adhesive for stability. This capacitor is in a sheltered area, so not as likely to be disturbed.

Out of curiousity, were the old caps bad?

You could also post a WTB for the entire board and/or workable 25EC58 chassis.

The 25EC58 was not rare. I am seeing 2 on FB MP in the midwest, both working, one is a non-remote Avanti. You are very dedicated to this TV, having a good working baseline chassis could be a great advantage....

I would consider the flyback a last last resort on the jail bars.

Do you have a spare HV tripler?

I'm not familiar with the BK 470, someone who is will have to comment on your CRT test. From the pictures you have posted it appears you have the brightness on the low side, in a darkened room, good focus and gray scale. It would be interesting to see how it looks with the brightness up a little bit.

TinCanAlley · #**104** 04-24-2026, 09:33 AM

Quote:

Originally Posted by BeamT

Hopping over the adjacent trace would be acceptable in this application. I would suggest using a short piece of spaghetti tubing to insulate the lead over the hop. You might also consider potting the electrolytic in a very small amount of adhesive to give it some mechanical stability. You could also gently scrape off the enamel on a small area at the end of the remaining trace to create a new pad. Form the lead to recreate the path of the missing trace, and solder to the pad you created. Consider potting the lead in a very small amount of adhesive for stability. This capacitor is in a sheltered area, so not as likely to be disturbed.

Out of curiousity, were the old caps bad?

You could also post a WTB for the entire board and/or workable 25EC58 chassis.

The 25EC58 was not rare. I am seeing 2 on FB MP in the midwest, both working, one is a non-remote Avanti. You are very dedicated to this TV, having a good working baseline chassis could be a great advantage....

I would consider the flyback a last last resort on the jail bars.

Do you have a spare HV tripler?

I'm not familiar with the BK 470, someone who is will have to comment on your CRT test. From the pictures you have posted it appears you have the brightness on the low side, in a darkened room, good focus and gray scale. It would be interesting to see how it looks with the brightness up a little bit.

The traces on this board are very fragile it seems, so I would be hesitant in scraping off anything to expose more. I will go the route of attaching to the other lead and using some of the tubing I have to cover the exposed lead. I have a glue gun, but am not sure if hot glue is acidic in the long term.

From that board, there is a 1uf that is 123% out of spec. It is showing as 2.23uf. There is a 50uf that is connected to the AFC to ground that is 26% out. It shows as 63uf. The rest are just under 20%. As for a replacement board, I found an NOS, but will get that as a last resort.

I'd like to keep the set as original as possible, so don't really want to swap in another chassis. If all my work doesn't rid me of the jailbars, I will live with it and possibly tackle it again in the future when I have more knowledge.

I don't have a spare OEM tripler, but I do have the NTE replacement that I got for possible future need. The set has the original tripler and the only thing I needed to change with the focus divider.

It's going to be interesting getting the assembly back together. I need to line up two gears so their wipers touch the proper pads on the boards. If they get out of alignment, the wrong light will illuminate with the wrong channel. Either from the factory or afterwards, there is a red mark on one gear and a black on the other. If you line them up, they are properly aligned. However, you now need to place the board on top of them without disturbing that alignment. What makes it difficult is the wipers are such that they act as springs, so the gears aren't sitting flush until the board is placed on top of them to seat them. See attached.

While frustrating at times, I am enjoying the challenge and gathering knowledge along the way. I am quite attached to this set as I've always wanted one since the first time I saw one. I have one now and I'm dedicated in restoring and preserving it for the future.

TinCanAlley · #**105** 04-24-2026, 10:48 AM

Not my best work, but it should hold. Checked continuity to surrounding components and all is well.

Also, guess Zenith thought of everything, but not having the SM for this assembly, I stumbled across it by accident. The issue with lining up the gears and making sure they were still aligned after assembly seemed an impossible task, but it seems there is a small hole in the board, right above the point where the two gears mesh and it is used to verify the red and black are correct. I used my video microscope over the hole with a bright light and could see the black tooth of one gear between the two red teeth of the other gear. Hard to see colors in pic, but they are there.