(TL DR the iron tuning slugs in both the audio and IF sections were crumbling into dust, throwing off the inductance, and throwing off the IF alignment)


Just when I think I’ve gotten out of the vintage TV collecting habit, I get pulled back in!

https://images2.imgbox.com/11/9a/mUfexVDx_o.jpg

It’s an RCA CTC 120 console set. It’s nothing special, except, it was just two houses from where I live, it’s in pretty good cosmetic condition, and it even still has the original power cord.

I first saw this TV while making a pit stop at home, and I said to myself “I don’t need it. I don’t need it. I don’t need it!”

I mean, I have an RCA Dimensia from November 1987, just before Thomson bought them. I don’t need a Mid-Tier Colortrak from 1983 that doesn’t even have A/V inputs!

So, I left it there, went back to work figuring a scrapper would come and get it and that would be the end of that.

I got home 3 hours later, and unfortunately it was still there, and still had the power cord.

As if to underscore that I was meant to save this TV, a scrapper pulled up right as I was wrestling it into the house.

https://images2.imgbox.com/10/5c/tzlyIke7_o.jpg
"Grandma, you need to keep the TV on Channel 3! Use this remote to find Jeopardy!"

So I let it get up to ambient temperature and plugged it in, and unfortunately, it turned right on and soon displayed a picture. You see, I was looking for justification to put it back out on the curb. But it came right on and displayed snow on the screen.

The snow on the screen was rather dim, and had a green tint. And, oh, the Black Level and Picture controls were maxed out. Yes! That’s exactly what I had hoped for! The CRT might be shot! That means I can get rid of this thing! Can’t justify keeping it if it has a bad CRT!

No wait, early 80’s RCA CRT’s tend to hold up pretty well. At least check the bias controls on the back of the set.

Unfortunately, there was plenty of room left on the drive and bias controls, and even with them turned all the way down, there was still a visible, albeit dim picture on the screen. And with the brightness cranked up, there is no color bleeding. The focus and geometry all look pretty good.

Well, shoot. It looks like the CRT is okay. Were it 10 years ago I would probably have thrown it out anyway, but these days, finding an early 80’s RCA, in this good of cosmetic shape... I’d be a fool to throw it away. Good working CRT sets are starting to get rare and to have one this nice practically handed to me…

Well I guess I’m its caretaker now.

There is one problem. The tuner is acting weird.

This was testing with my HackRF using HackTV on Channel 2:
https://images2.imgbox.com/83/7d/mX1jmwwk_o.jpg

And this was Channel 3, same power output:
https://images2.imgbox.com/83/2d/dHvKTkmi_o.jpg


To verify that it wasn't an issue with my hackRF, I tried a known good DTV converter box:
https://images2.imgbox.com/40/d2/RVx4j2NY_o.jpg

I am certain it's an issue with the tuner, because testing on UHF produces a better picture, and I was able to (once) get a crystal clear black and white image with no distortion.


Additionally, despite the worn buttons in the front, I don't think this is a very high hour set. The screws in the back haven't been taken out often, or at all before I got to it:
https://images2.imgbox.com/2d/62/h7mPfGXl_o.jpg

And the inside is weirdly clean:
https://images2.imgbox.com/1d/76/WdGENv9y_o.jpg

I mean there's some dust, but not as much as I would expect for a 40 year old television that, supposedly, has seen high usage.

Pull & resolder the tuning modules. Especially at connectors. Watch
for cold grounds around shields. There are several 'lytic caps that
filter supply voltages. By the looks it may be on the @33 Volt tuning
supply. These tuners kept stakes on the table for us.

Zeno:smoke:

Okay so, bad solder connections likely in the tuner. That should be easy to fix.

Where would I find the capacitor(s) in that 33 volt tuning supply? I'm terrible with schematics. I do much better knowing where it physically is on the circuit board.

Pretty sure it's not a bad solder connection in the tuner. I reflowed everything that looked questionable to me, and there is no change. And that ripple in the picture is telling me there's a bad capacitor somewhere.

While I was in there I took out that button pad, and the #3 button has been pressed so much that it broke off the plastic tab, which I find to be kind of funny. Stupid yet hilarious early 80's design. (WE MUST HAVE BUTTONS!)

So i fixed it with some HVAC tape:
https://images2.imgbox.com/d1/f5/69WhyM1j_o.jpg

Channel 3 button, huh? This set has probably seen a lot of video games.

Channel 3 button, huh? This set has probably seen a lot of video games.

Or, ya know, DTV converter boxes, cable boxes, etc...

I don't think this TV has ever been serviced before:

It's still got the original straps holding the wiring in place, and holding the CRT neck board on. (https://images2.imgbox.com/92/ec/vs3D8Yxx_o.jpg)

I don't think the chassis has ever been out of this set.

I said this set was nothing special. I take that back. This thing survived 40 years of use, and still has life left in it. It didn't eat its flyback, or the HOT. It didn't overheat. It didn't even pop its fuse! That's pretty special.

I have pulled and tested multiple capacitors. They all test fine. Good ESR, values within spec.
I have reflowed many questionable solder joints.
I have taken apart the tuner and reflowed any questionable solder joint I could find.

Zero change.

There is a horizontal ripple in the image when something like bright lettering is on the screen. Also, the audio sounds a little bit distorted.

I am not sure where to go from here, but I am wondering if i should start tweaking coils. Maybe 40 years of use caused the tuner IF to drift a bit?


Additionally, working on this TV is hard when you have a cat:

Human! Human I need you to stop everything you're doing and give me attention!! (https://images2.imgbox.com/de/40/rf5VIfpG_o.jpg)

Some help on what to try next would be appreciated. I can post video of how the set is acting if it will help.

Some help on what to try next would be appreciated. I can post video of how the set is acting if it will help.

Zeno is much better tech than I, but it looks like horizontal sync problems to me. Either caused by the tuner being dirty or something else. I remember seeing that kind of symptom and getting rid of it by grinding the tuning knob back and forth a bunch with deoxit in there.

I'm assuming you tried that and it didn't help though.

I guess the next step if no one else has any "known faults" to try, and you poked around for anything obvious already (caps with guts spewed or burnt spots on the PCB or reflowed solder), then the next step is to start checking voltages and hope you find a problem that way.

Problem is that I don't know that a sync problem would always manifest as a voltage issue. It's possible that something is just out of alignment. You never know if someone else got there first and started tweaking stuff. To do an IF alignment, I think you probably need a signal generator that can do a carrier wave or whathaveyou. I have never been able to do that because I lack that equipment. Perhaps there is some way to fake it with a normal signal generator, but idk.

If you have the schematics, you can at least check the main power supplies just to do a sanity check. I've caught a lot of BS that way. Otherwise if you don't have the schematic (better yet the SM), not sure how you'd do anything else beyond poking around.

Zeno is much better tech than I, but it looks like horizontal sync problems to me. Either caused by the tuner being dirty or something else. I remember seeing that kind of symptom and getting rid of it by grinding the tuning knob back and forth a bunch with deoxit in there.


Uhhh... This is the 80's. WE MUST HAVE BUTTONS! (https://images2.imgbox.com/10/5c/tzlyIke7_o.jpg)

Yeah this TV has one of those early digital tuners. No tuning knob to clean. And, as surprising as it sounds, I don't think *anyone* was in the set before me.

I don't have service data and this set's not worth me buying a SAMS just for it. I kinda gave up on TV repair years ago. I'm only trying to fix this one because it practically fell into my lap.

Now if I knew what voltages to expect yes I'd check those.

UHF is not as affected, and with a good strong signal on a UHF channel, i can get a good picture. That tells me I can rule out the deflection circuits.

But it's really looking like alignment drift. Because I can see those squiggly lines when the sound bleeds into the video.


EDIT: Did a search here and found a couple posts about bad filter capacitors causing a "twisted" picture. So I pulled the filter cap and tested the sections.

Filter cap tests fine. The 30uf section tests at 41uf which is a bit high, but the ESR tests fine. The 600uf section is right on point.

There are two trim pot controls located in the top left corner of the chassis. They are labeled "AFT balance", mark where they are and see if adjusting them makes any difference, if not, set them back where they were. If the controls don't help, aligning the AFT crossover coil may help. It should be labeled on top of the metal shield L304 on the left side. To adjust the coil, with the set on and tuned to a channel, turn the coil slightly in one direction, less than one turn, then interrupt the signal by switching to 04, the back to 03. Each time the coil is turned the set needs to fine tune itself that's why the signal must be interrupted. Also check and clean the sharpness control on the back apron of the chassis. The sound may be cleared up by aligning coil L201, it's just in front of the audio IC where the speaker wires connect. This coil uses a different alignment tool than the AFT coil one. There should be a paper chart in the cabinet that show these parts locations.

Interesting. I noted the sharpness control doesn't seem to do much. I didn't mention it because the picture looks fine.

I have a set of ceramic screwdrivers coming. When i get them I'll start tweaking coils.

I don't have service data and this set's not worth me buying a SAMS just for it. I kinda gave up on TV repair years ago. I'm only trying to fix this one because it practically fell into my lap.


woof. Honestly I just get a manual whatever I can if I'm doing a repair because it always saves so much time, and 20 bucks ain't much time these days.

There's no reason to fight it. You fix TVs again now. All is right with the universe.

There are two trim pot controls located in the top left corner of the chassis. They are labeled "AFT balance", mark where they are and see if adjusting them makes any difference, if not, set them back where they were. If the controls don't help, aligning the AFT crossover coil may help. It should be labeled on top of the metal shield L304 on the left side. To adjust the coil, with the set on and tuned to a channel, turn the coil slightly in one direction, less than one turn, then interrupt the signal by switching to 04, the back to 03. Each time the coil is turned the set needs to fine tune itself that's why the signal must be interrupted. Also check and clean the sharpness control on the back apron of the chassis. The sound may be cleared up by aligning coil L201, it's just in front of the audio IC where the speaker wires connect. This coil uses a different alignment tool than the AFT coil one. There should be a paper chart in the cabinet that show these parts locations.

adjusting one of the AFT balance trim pots helped a little bit.

Adjusting L304 really affected things.

I wish I could tell you more, but the ceramic bits I ordered are too #$%^&* short to properly reach the slug... so i'm waiting on a set of proper coil alignment screwdrivers. :sigh:

Also sprayed deoxit into the sharpness control.

Are
You
Kidding
Me

The set of plastic alignment screwdrivers showed up today. Two of the fit L304.

L304 stripped one, and broke the tip off the other. The plastic tip is now jammed in L304.

This was ***AFTER*** using Deoxit to help free up the coil.

I am about furious enough to do a radiotvnut and EOL this "thang", but at the same time, I am not going to be beaten by a freaking IF coil.

So I'm probably going to desolder it one day when I have time and try to free it up.

Are
You
Kidding
Me


Holy yeah man. Those things can get good and jammed up in there. I've seen people taken them apart to find they were glued or waxed in place before at the factory as well, but I don't know how common that actually is.

Ah, well hello there, you little b******! (https://images2.imgbox.com/10/95/Gv8QCX42_o.jpg)

Meet L304. The coil that has been giving me no end of trouble. More specifically, meet the iron slug inside L304... which CRUMBLES! INTO! DUST! with every tool I try to use to turn it!!

There is no turning that iron slug. It's just breaking apart inside the coil.

Okay... You know... I no longer want that slug out of the coil... I've decided it's coming out of that coil!

https://images2.imgbox.com/47/30/mWmxfYZU_o.jpg

It took multiple Q-tips soaked in rubbing alcohol to get all of it out of there, but it's out of there now.

And now I am hunting online for a replacement slug to go into it, because, like i said, I am not going to be beaten by an IF coil.

Stubbornness mixed with patience and skill can be fun sometimes.

I hope you find a good usable slug. It likely should not be too hard, maybe you can find a variety pack/old pile of coils with slugs and try them until one has the needed effects.

Stubbornness mixed with patience and skill can be fun sometimes.

I hope you find a good usable slug. It likely should not be too hard, maybe you can find a variety pack/old pile of coils with slugs and try them until one has the needed effects.

I have a coil coming from eBay. It has the same number of turns as this coil and looks to be the right size. So either the slug will fit or the coil will fit.

I tried sourcing a slug from a pair of those 49Mhz toy walkie talkies (Funny thing, they still cost $10, decades later...) But the slug was too small. Coil might work though, if I were desperate. TV IF is 45 Mhz and toy walkie talkies are 49 Mhz so the coil has to be pretty close.

Ladies and Gentlemen I found a replacement tuning slug!
https://images2.imgbox.com/bc/99/j8EI6zYR_o.jpg

The slug came from an Ebay ad titled ".17 - .25 variable RF inductor vintage PC mount adjustable radio tuning coil NOS"

The slug appears to be a 4.35mm slug about half an inch tall.

Putting the new slug in and making adjustments to it and the AFT balance pots has certainly improved things:
https://images2.imgbox.com/d8/49/LhDti4fF_o.jpg

However I am still getting audio crosstalk in the picture, and the audio sounds a little bit strange. The volume is fine, but the Treble, especially S sounds are distorted at any volume.

So, definitely better, but it's not all the way there yet.

Find & adj the 4.5 trap. Put a flag on your stick so you can go back
Zeno:smoke:

Find & adj the 4.5 trap. Put a flag on your stick so you can go back
Zeno:smoke:

Adjusting the 4.5 trap, if anything, made the issue slightly worse.

And it took multiple turns to have any effect at all.

I'm thinking the slug inside that coil is probably crumbling as well. I tried bottoming it out and my screwdriver just kept turning. I'm thinking if I get another slug and replace it, that might be the whole issue.

I have an 1983 RCA with same problem with the sound. The TV has a lot of hours on it but it still has a good tube. The tunner muduler was worked on in the early 90s but other than that it looks untouched. I need to get some adjustment tools so I can try adjust the IF can.

I have an 1983 RCA with same problem with the sound. The TV has a lot of hours on it but it still has a good tube. The tunner muduler was worked on in the early 90s but other than that it looks untouched. I need to get some adjustment tools so I can try adjust the IF can.


Searching this forum has told me that L201 is probably the culprit for sound, if not the 4.5 trap.

But I think those powdered iron slugs have degraded over the past 4 decades, and I think that has thrown off the inductance of the coils.

When I get time, and more slugs, I plan to replace the slugs in L201 and the 4.5 trap.

Got several replacement coils with tuning slugs in them today. (https://images2.imgbox.com/5a/3b/JI0yY8kd_o.jpg)

Pirate Pete Electronics is the eBay seller, in case you're somebody whose looking for these slugs.

So at some point I am going to pull that chassis board, again, desolder the IF shield, again, and replace a tuning slug... again.

Oh, did I mention I have little experience with IF alignment, and I don't have a scope? This is going to be FUN!!

"Just the fact that you're trying to align IF coils, with no scope and little experience means you are either really brave... or really crazy!"
"Well, I'm certainly not brave!" :nutz:

Realistically there's no point in trying to get perfect alignment. After all, there's nothing for the tuner to receive anymore, apart from whatever an RF modulator feeds it.

Oh. Goody. The tuning slug in L201 is disintegrating just like the one in L304.

That would explain the distorted audio, and the wavy lines in the picture from audio crosstalk. So yay... Happy Easter... I don't know where RCA got these tuning slugs, but these were definitely a bad batch, and probably why the CTC 120 is known for IF and audio problems.

It's an Easter resurrection! (https://youtu.be/DNPN7MK_bVQ)

Here it is, Easter Sunday 2025, and I have a resurrection of my own to celebrate! After replacing slugs in L304, and L201, I was able to get the I.F working *Good enough!*

Is it perfect? No. I don't have a scope. I don't have test equipment. What I do have is perseverance. I think the replacement slugs were not meant for this TV as I had to adjust basically every coil in the IF and audio sections. A LOT of trial and error! This took me hours to get the picture you see in the video!

But it locks solid. The audio crosstalk is basically gone. It's not perfectly aligned, but it's way, way better than when I found it!

And I have further evidence that this set is not a high hour set, despite the worn buttons. The Screen control on the back of the CRT had plenty of room left on it. I don't think it was ever touched.

Screen controls at factory default, plenty of room left on the drive and bias controls... I think I have a pretty good CRT here.

So... Now that I have this thing fixed, or at least as fixed as I'm going to make it... I am going to do what we used to do with console TV's back when i was a kid:

It's going to go up against a wall, I'm going to put a towel over the top, and use it as a table to set stuff on. Occasionally I'll plug it in and turn it on to remind myself that yes, I diagnosed and fixed this damn thing, and documented that the tuning slugs in CTC 120's can crumble into dust.

It's an Easter resurrection! (https://youtu.be/DNPN7MK_bVQ)



Great work!

The colors look fantastic.

Congratulations ! Looks very good. We sold a lot of those sets and many customers continued using them with converter boxes past the digital change over. Except for lightning, it was hard to kill them.

Congratulations ! Looks very good.

It's *okay*.

The picture has a lot of ringing in it, particularly visiblle when reading small text, and there is a buzz when the picture shows white lettering against a dark background.

I don't know if it's worth me trying to fix, especially since I have an RCA Dimensia which has a way better tuner.

The ringing is probably due to a mistuned IF coil, perhaps a sound trap that's tuned somewhere in the video band instead of at sound frequency. No way of telling for sure what it is without the proper alignment gear.

The ringing is probably due to a mistuned IF coil, perhaps a sound trap that's tuned somewhere in the video band instead of at sound frequency. No way of telling for sure what it is without the proper alignment gear.

Given I had to adjust pretty much EVERY tuning slug in the IF section because I had to replace 2 that crumbled...

But, which one would be the cause? L304? The 4.5 trap? Something in the audio section?

Given I had to adjust pretty much EVERY tuning slug in the IF section because I had to replace 2 that crumbled...

But, which one would be the cause? L304? The 4.5 trap? Something in the audio section?

I could not, would not, make a guess. The real answer is to get the necessary test gear and do it right.

However, if you promise not to blame anyone but yourself if it gets worse, you could try more very slow random adjustments, and see if there's one that strongly affects the ringing.

Edit: not anything in the audio section.

The real answer is to get the necessary test gear and do it right.


Just for my own edification, what is the proper test equipment (other than a scope and a multimeter)?

You could check out Shango066 on Youtube. he's done videos on IF alignment.

What I might do, some day is mark where the 4.5 trap is set at, and try adjusting just *that* coil and see what happens. My suspicion is the 4.5 trap is adjusted into the audio band.

Just for my own edification, what is the proper test equipment (other than a scope and a multimeter)?

A sweep/marker generator.