RCA CTC-16XL Suggestions/Tips

[Rocket]

Originally Posted by Electronic M

Something akin to these is what I use. https://www.alliedelec.com/circuit-p...20Stock%20Only

The way I understand it there is a motor run cap inside that regulates the power through a resonance effect. They can hold outut voltage rock stable with anything between 90-140 input...Heck they can even hold stable output voltage through a missing cycle or two of input.

I see new ones are stupid expensive...I got all of mine by haunting Hamfests and antique radio swapmets...I don't think I paid over $25 a pop for mine. Every one of the 4 I've got was a good purchase, and I'm still lookin for more.

The advantage of a CVT is there is no switch mode supply to potentially generate RF hash on the line...Also fewer parts means less to go wrong.

Wow that's impressive it can hold stable of a missing a cycle or 2! Probably more efficient than the ac-dc kind as well. Really don't want any RF hash on the line as well. It is a shame they are so expensive. I will have to keep an eye out at the swapmeets and perhaps I can pick up one for a better price.

[Rocket]

Well I did my first power up today to check my progress and it looks as though I have made my situation worse. I lost even more of my vertical height, was just a horizontal line at first, but the controls let me bring the line down a few inch's. I was able to bring up the upper vertical but not as much as before as well. but it looks like most of the picture is squeezed in a few inch's. I did try another vertical tube just to rule it out.

Here's what I've done so far,
Cleaned up all the pot controls and switches and they all seem to work much better now. cleaned up all the tube pins and sockets with DeOxit

replaced 2 paper/wax caps under the hood
Also under the hood R130 and R125 connected on the horizontal output tube was pretty well out of tol.
I also replaced that 150K everyone talked about, think that was r104. it drifted to about 8% so I nabbed it also.

up top on the sweep board R97 was past the edge so I replaced that one. Had to lift R82 to read it and it wasn't too bad but had drifted a bit so I nabbed it.

Going to pull the chassis back out tomorrow and recheck all my work.

Any suggestions on where to look and test for I'm all open ears

[Electronic M]

Start with all the electrolytic caps in the vertical (IIRC one is mounted on the convergence board). Change the orange/maroon drops in the vertical stage too if the lytics are not it. Many say drops don't fail, but in sweep stages and some in the color stages close to tubes do go bad in these sets (I've tested caps for leakage to full working voltage on my Heathkit C3 to learn this).

[Yamamaya42]

Originally Posted by Rocket

Well I did my first power up today to check my progress and it looks as though I have made my situation worse. I lost even more of my vertical height, was just a horizontal line at first, but the controls let me bring the line down a few inch's. I was able to bring up the upper vertical but not as much as before as well. but it looks like most of the picture is squeezed in a few inch's. I did try another vertical tube just to rule it out.

Here's what I've done so far,
Cleaned up all the pot controls and switches and they all seem to work much better now. cleaned up all the tube pins and sockets with DeOxit

replaced 2 paper/wax caps under the hood
Also under the hood R130 and R125 connected on the horizontal output tube was pretty well out of tol.
I also replaced that 150K everyone talked about, think that was r104. it drifted to about 8% so I nabbed it also.

up top on the sweep board R97 was past the edge so I replaced that one. Had to lift R82 to read it and it wasn't too bad but had drifted a bit so I nabbed it.

Going to pull the chassis back out tomorrow and recheck all my work.

Any suggestions on where to look and test for I'm all open ears

That's why I chose not to do too much of an area at once, example, my first target was the v6 area, replace what I think may be bad, then re-power on to see if there is any drastic change.
My next target is the V1/V2 area.

Pick a section at a time, and test the set a LOT as you go.

[Rocket]

I believe I have all the electro's changed out except for the 3 big cans, and I was contemplating them, but I wanted to test the set first to see how things were looking. I will pull the chassis back out after work today and check my work, then check to make sure about all the electro's, I need to take a look at the convergence as I have not done that. I did clean up all the pot controls on it with DeOxit though. then if all looks well, I will start on the drops. I don't have a way to test to full voltage so I may just get all the drops in the vertical section.

yeah, not a bad idea about testing the set as you go : D

[Rocket]

Originally Posted by Electronic M

Start with all the electrolytic caps in the vertical (IIRC one is mounted on the convergence board). Change the orange/maroon drops in the vertical stage too if the lytics are not it. Many say drops don't fail, but in sweep stages and some in the color stages close to tubes do go bad in these sets (I've tested caps for leakage to full working voltage on my Heathkit C3 to learn this).

This did the trick Tom! I went ahead and replaced all the orange/maroon drops on the sweep board and vertical is working perfectly sized up perfect and easily, locks in perfect with a wide range.

The horizontal has a lot left to be desired. it can be centered, but with controls at almost their max.

I am contemplating going though and getting the rest of the orange/maroon drops on all the other boards and re stuffing them 3 electro cans.. what's your option Tom on that doing that? My largest fear is putting the set out of alignment by changing out all them caps.

[old_tv_nut]

Hint: any circuit that is "tuned" for correct operation will have an adjustable component, like a coil or potentiometer. If the fixed-value caps are way out of tolerance, the circuit is already detuned, and the best thing is to replace these and retune the circuit.

Note that the small ceramic or mica caps that tune the IF or tuner are seldom bad, compared to the larger paper or film caps or electrolytics in sweep circuits, etc., so it's not a good idea to blanket replace those small ones that tune IF or RF circuits. IF re-alignment is a chore, so if it's not broke, don't fix it.

But the paper or wax caps or electrolytics that affect sweep operation or are B+ bypasses, or large cathode bypasses (like the video output) etc. are worth replacing when things don't work right. The retuning then consists of adjusting the sweep size and linearity, for example, which will work much better if the fixed resistors and caps are within tolerance.

[Electronic M]

Originally Posted by Rocket

This did the trick Tom! I went ahead and replaced all the orange/maroon drops on the sweep board and vertical is working perfectly sized up perfect and easily, locks in perfect with a wide range.

The horizontal has a lot left to be desired. it can be centered, but with controls at almost their max.

I am contemplating going though and getting the rest of the orange/maroon drops on all the other boards and re stuffing them 3 electro cans.. what's your option Tom on that doing that? My largest fear is putting the set out of alignment by changing out all them caps.

If a stage is not operating well changing the drop caps and lytics is completely advisable. If any lytics get warm in operation (even if it takes better than 30min to get there) replacement is more than optional, it is necessary.

The CTC-16 I did I have limited memory of (it was a fast resto), but on my Silvertone CTC-15 clone (though it might have been old enough for the chassis to be RCA made*) I went slow and learned much...That set worked okay with the maroon drops in it, but many stages especially the color demod/video board benefitted greatly from the replacement of all the maroon drops. If performance seems lacking change those caps. One thing to note with most drop caps most were either plastic film or plastic/paper hybrid dielectric...They may very rarely leak current, but the early hybrid caps have degradation of the paper that will drift the tolerance of the capacitance value well out of tolerance...Most will still pass signal, filter, bypass, create a time constant (or whatever their specific job was) in a passable manner, but will be collctively far enough off optimum to notice.

*Pre 1963 nearly every chassis that was an RCA design used in a smaller brand was RCA made, then sometime in 63 RCA stopped selling chassis to other brands and those brands either built RCA chassis under license or designed their own chassis (some made clones for a while then switched to their own designs).

I rambled too much didn't I...

[Rocket]

Originally Posted by Electronic M

If a stage is not operating well changing the drop caps and lytics is completely advisable. If any lytics get warm in operation (even if it takes better than 30min to get there) replacement is more than optional, it is necessary.

The CTC-16 I did I have limited memory of (it was a fast resto), but on my Silvertone CTC-15 clone (though it might have been old enough for the chassis to be RCA made*) I went slow and learned much...That set worked okay with the maroon drops in it, but many stages especially the color demod/video board benefitted greatly from the replacement of all the maroon drops. If performance seems lacking change those caps. One thing to note with most drop caps most were either plastic film or plastic/paper hybrid dielectric...They may very rarely leak current, but the early hybrid caps have degradation of the paper that will drift the tolerance of the capacitance value well out of tolerance...Most will still pass signal, filter, bypass, create a time constant (or whatever their specific job was) in a passable manner, but will be collctively far enough off optimum to notice.

*Pre 1963 nearly every chassis that was an RCA design used in a smaller brand was RCA made, then sometime in 63 RCA stopped selling chassis to other brands and those brands either built RCA chassis under license or designed their own chassis (some made clones for a while then switched to their own designs).

I rambled too much didn't I...

Not at all! : D I sure love hearing and learning about all about this stuff

I will check on the cans and see if they get warm at all. Probably get the drops changed out and check on that horizontal

[Rocket]

Update,

Got the set working and looking better so far. I got some practice in doing purity and convergence setups and that was pretty cool and its looking pretty good. though not quite where it needs to be.

HV output was 16kv at about 175ma. I was able to bring that up to 24kv, that brought me up to around 210ma, I was able to get that down to around 200ma

Some fields on convergence can get sorta close with their pots at max, so I am going to check out some resistors and see if anything is outta range.

I noticed the sharpness/focus adjust does not have any effect. it looks like that coil has had work done in the past. so gotta figure that out as well, its a little off.

One of the 3 metal electro cans started getting warm after running a while, guess I know what I am going to be doing about that hehe

However something that kinda has me wondering what is up and I am not sure if I want to run the set more until I know what is going on,
about 4 hours of running as I was working on the set I started getting a hiss like sound coming from high voltage area. Letting the set sit overnight and firing it up this morning, did not have that hiss sound until about 15 minutes of running and then it returned. Any ideas what that is about?

And I got a picture of my first time doing a purity and convergence setup!

[Yamamaya42]

Originally Posted by Rocket

Update,

Got the set working and looking better so far. I got some practice in doing purity and convergence setups and that was pretty cool and its looking pretty good. though not quite where it needs to be.

HV output was 16kv at about 175ma. I was able to bring that up to 24kv, that brought me up to around 210ma, I was able to get that down to around 200ma

Some fields on convergence can get sorta close with their pots at max, so I am going to check out some resistors and see if anything is outta range.

I noticed the sharpness/focus adjust does not have any effect. it looks like that coil has had work done in the past. so gotta figure that out as well, its a little off.

One of the 3 metal electro cans started getting warm after running a while, guess I know what I am going to be doing about that hehe

However something that kinda has me wondering what is up and I am not sure if I want to run the set more until I know what is going on,
about 4 hours of running as I was working on the set I started getting a hiss like sound coming from high voltage area. Letting the set sit overnight and firing it up this morning, did not have that hiss sound until about 15 minutes of running and then it returned. Any ideas what that is about?

And I got a picture of my first time doing a purity and convergence setup!

I can't cout how many times I have done the convergence and purity dance. if i had to say, it's in the 100s huge:

[Electronic M]

Dynamic convergence tip: if the board is fine but it is pretty far off at all pot settings try moving the convergence yoke as much as 1/4" forward or rearward of it's designed position (over the end flare of the electron gun/or red dag ring if the gun is hidden). Sometimes The dynamic field overall is too strong or too weak and moving it fore/aft can act as a mechanical gain control. If the outer 1-2" radius is kinda lousy but looks decent from 15-20' viewing distance you may have optimized it. Perfect convergence to the edges on a roundy is a rare achievement.

Some focus ideas: there should be a ~3-6KV ceramic cap on the focus coil that may not be holding correct capacitance value. IIRC the 16 is tube focus rectification...I tend to switch most focus rects to modern SS HV diodes. Removing the filament load relieves the flyback, and tube focus rects are not always as stable as I like.

If you can get the HV cage open to look for arcing/corona that may help.

[Yamamaya42]

Originally Posted by Electronic M

Dynamic convergence tip: if the board is fine but it is pretty far off at all pot settings try moving the convergence yoke as much as 1/4" forward or rearward of it's designed position (over the end flare of the electron gun/or red dag ring if the gun is hidden). Sometimes The dynamic field overall is too strong or too weak and moving it fore/aft can act as a mechanical gain control. If the outer 1-2" radius is kinda lousy but looks decent from 15-20' viewing distance you may have optimized it. Perfect convergence to the edges on a roundy is a rare achievement.

Some focus ideas: there should be a ~3-6KV ceramic cap on the focus coil that may not be holding correct capacitance value. IIRC the 16 is tube focus rectification...I tend to switch most focus rects to modern SS HV diodes. Removing the filament load relieves the flyback, and tube focus rects are not always as stable as I like.

If you can get the HV cage open to look for arcing/corona that may help.

They did once make solid state sub for the HV rec (NTE508) if you could find one, would using one also lessen the load on the FB? ans what would one replace the focus rect (2AV2) with?

[Electronic M]

Originally Posted by Yamamaya42

They did once make solid state sub for the HV rec (NTE508) if you could find one, would using one also lessen the load on the FB? and what would one replace the focus rect (2AV2) with?

This should work: https://www.mouser.com/ProductDetail...7ob59eZhXAY%3D

I have 4 in series for the focus rect in my CTC2B...Granted that set uses three 3A2s for focus, HV rect, and HV doubling...Also the 3A2 has 18KV PIV rating so putting 4 5KV PIV rated diodes in series for a combined 20KV was cheap insurance against someone swapping the tubes around. (I also built a second one that I've been using in one of the HV positions in that set).

Before I looked up these modern diodes up I had a few selenium focus rect sticks from CTC-15 and similar sets that I used to eliminate the tube focus rect in a Zenith roundy and some other sets.

It will definitely reduce flyback loading since the filament of the focus rect tube pulls its filament power from the energy in the flyback

[Rocket]

Originally Posted by Yamamaya42

I can't cout how many times I have done the convergence and purity dance. if i had to say, it's in the 100s huge:

Thats crazy huge!

Originally Posted by Electronic M

Dynamic convergence tip: if the board is fine but it is pretty far off at all pot settings try moving the convergence yoke as much as 1/4" forward or rearward of it's designed position (over the end flare of the electron gun/or red dag ring if the gun is hidden). Sometimes The dynamic field overall is too strong or too weak and moving it fore/aft can act as a mechanical gain control. If the outer 1-2" radius is kinda lousy but looks decent from 15-20' viewing distance you may have optimized it. Perfect convergence to the edges on a roundy is a rare achievement.

Some focus ideas: there should be a ~3-6KV ceramic cap on the focus coil that may not be holding correct capacitance value. IIRC the 16 is tube focus rectification...I tend to switch most focus rects to modern SS HV diodes. Removing the filament load relieves the flyback, and tube focus rects are not always as stable as I like.

If you can get the HV cage open to look for arcing/corona that may help.

Ah! that's awesome to know! I may have to check that out and see how that changes things. But yeah, there is a few spots on that very outer 1-2'' that is lousy. but you can't really tell when tuned into a broadcast and does look great from 10 feet back. its impressive the quality of the picture on these older sets!

Indeed you remember correctly, it does have a tube rectifier. And I am up for helping out that flyback. I did notice the ma's surge over 300 for a very brief moment when the tv is first turned on. How hard is that to do solid state conversion?

I am not sure what I am looking for on the arching/corona. Do I need to do that check when the tv is running? I did notice that there was a static build up on the lead coming from the top of the hv cage. I did attach a few pictures of the flyback as well. I have a hunch that I am going to doing that flyback surgery to remove the rubber and do a silicon coating.