My CTC-16XL Project.
 

The story so far: In the beginning the Universe was created. This has made a lot of people very angry and has been widely regarded as a bad move...

Wait a sec, that's the Hitchhiker's guide to the galaxy... :)

The story of this RCA, found ( rescued ) from a High School vocational electronics class, ( original problem , no color ), after some pretty dumb things were done to it, including , removing the color PCB.

I tried to fix it back then, but did not have much time to devote to it, since then, It has sat in storage waiting all these years, exposed to the cold of winter and the heat of summer. ( I'm sure the caps hated this, especially the electrolytics)

Last dec, I decided to pull it out and start working on it again, after much checking, I'm pretty sure ( not 100% ) that the color PCB is back in and hooked up correctly.
So, I dared to turn it on... no smoke, no explosions, no popped breakers, and after replacing the bad HV rec and reg, I got High voltage, and a raster ( very ugly ) no video yet. 21Fjp22a in great shape 3 good guns.

I'm still in the process of changing the main electrolytics, but I did see something a bit strange, C1a has been changed, but I still see a strong sawtooth wave there (before L45 and not after ) at about 10v when first turned on raising to 30v as tubes warm up and HV kicks on.

I'm pretty sure that sawtooth should not be there, or be that high, as mentioned, C1A has been replaced, (85uf 500v ) I may try something larger, I have NOT replaced C3B yet ( it may be coming from there.) and plan to replace the other electrolytics 1 at a time, to see if this goes away, I am also in suspect of the main LV rect diodes, they MAY be flaky, orig replacements are hard to find, so I'm guessing that 1N4005G dioded should be OK.

Once I get power stable on this thing, then I can worry about cleaning all the dirty pots and switches ( and tuner :/ ) and trying to get a video to show on it again...
I'm hoping that deoxit is a good choice for cleaning the tuner. :/

As I mentioned, I am in the process of re-capping my RCA CTC-16XL,
The electrolytics mainly to start with, to get stable power, as it's been sitting for 30 years.
But there is one section in the multi cans, that does NOT look like power filtering, but part of AGC, and unlike the PWS section, if I replace with anything larger that what was in there, it can drastically change how it works.

C1 section c 40uf, ( see attached )
making a guess here, this is a feedback circuit off the output of video amp 2 , via the delay line, L13, L14, to set cathode bias on v6, (a/b) , so there is no wiggle room on that cap, it MUST be 40uf...
Am I reading it right?
https://imgur.com/a/iG2mCf6

C1 looks to be a cathode bypass/filter cap..... there's no such thing as a precision lytics in tube electronics....they all were rated -50% +100% capacitance tolerance. A 47uF or if your feeling persnickety a 39uF will both work fine.

40 is part of the old standard.of parts valuing that was on its way out when that set was new...So your not going to find a newly made 40.

Then the 56uF 80Volts cap I have should be OK then. but I'll replace that one last.

update
 

I may be overthinking this, but to me , this sawtooth wave here (at C1a) just does not seem right, but the SAMS does not have a reference for a wave at that exact point, I have replaced C1a with an much larger cap and am still seeing it, its mostly filtered out by L45, but I don't think it should be there at all, its still present at the end of the 400v source ( very faint )

I'm running the set with HV disabled ( yolk disconnected ) when this wave was captured.
I have not replaced the LV rects yet ( they are hard to get to ) but I plan to, as I suspect them to be a problem. ( unless someone thinks that sawtooth I'm seeing is normal :o ) as mentioned, I chose 1N4005G for that as they looked rather close to what was in there..

https://imgur.com/a/U5mvTBT
https://imgur.com/a/6vEuABP

next update
 

replacing the LV diodes did not make that sawtooth wave at that point any better, so i't most likely normal, I DO get the 1v wave, as shown in the Sams on the other side of L45, i'm 1/2 way through replacing the main filter caps.
I still need to clean all the POTs and the tuner, to try to get it to get some picture on the screen, however, I may just bypass the tuner and IF all together and tap in video at the 1st video amp, to save time, ( around L9 ) as shown below.
https://imgur.com/a/PHTuOE9

The one thing i dread the most is... once all the electronic stuff is out of the way, fixing that damn cataract. T_T

https://imgur.com/a/d7cvF8P

That cat don't look too bad...A little more and it would fall off on it's own. Come summer put it face up in a 5 gal bucket or trash can, remove the tape around the edge, with a VERY thin screwdriver gouge out several 1" radius chunks of the glue (don't pry on the glass), then take halves of wooden clothes pins and wedge them in to the radiuses you removed, place it in the sun with a black garbage bag over it's face. Every 15-30 min tap the wedges in a bit. Gradually the safety glass will come off...The biggest enemy is impatience I've ruined 2/3 of the safety glass I've done this on by applying too much force too fast.

When your done peel and fingernail scratch all the old glue off, clean bulk residue with goofoff, then get streak free with glass cleaner. You can reattach the safety glass by at 4 even spaces along the edge placing 1/8"-1/4" thich foam double stick tape strips as gap spacers. then caulk the edge. Make sure it is ABSOLUTELY spotless before setting the glass on (any dust, spot or lint will be a pain to go back and get). And make sure the spacers and caulk are at least 1/4" outside the edge of the phosphor viewing surface...(otherwise, when the CRT is in the set you'll see it and be sad).

What kind of sucks now is, there is no easy way to test tubes... long ago, when I was a kid, there were testers all over the place, but now, if you go asking for one, they look at you like you have 3 heads and tentacles for arms. And yes, you can find some old portable ones on E-bay, but who knows how well they work, ( if at all. ) :(

I've always considered drugstore testers as a waste of space.... get a portable like the B&K 606 I use predominantly.... any tester at this point is equally at risk of inaccurate readings. Most "portable" service testers have published service and calibration online. You can run thru a cal and if it fails just change a handful of resistors and caps and next time it should pass.

Also some tubes like sweep and HV cannot be accurately tested on any tester because no tester was made to deliver the high current and or high voltage the tube gets subjected to in normal applications. I seen plenty of HV rects and other sweep tubes where readings in multiple testers don't match actuall in set performance.

Nice anime catgirl avatar ya got.

If you're getting a sawtooth waveform at first filter capacitor, don't be too surprised. These sets use a voltage doubler power supply, and it's going to have lots of ripple at the first filter. In other words, I'd kind of expect a sawtooth there.

Where did you get C1A from? What cap is it on the RCA schematic? Is that a sams or an RCA part number?

https://www.boxcarcabin.com/rcaschematics.html has most of the early rca schematics.

I sold my CTC16 some time ago, but it was a cool TV. Make sure to check for bad soldering of power resistors, and also I'd go over the chassis ground points. The spots where the boards are soldered to the chassis can cause intermittent issues if the solder isn't good, it would be a good idea to re-flow them. Clean all the tube sockets too.

I'm going from the sams , that matches my CTC-16XL (set 812 folder 2 )
there is slight difference in the CTC-16 vs CTC-16X, so much that they have different releases . but both have full bridge rectifiers, and look nothing like voltage doubler in the link you shown (odd) , the bridge and C1 a is in a link i pasted above, Was 80uf, (400v) now is 100uf (500v)

I took a peek at all RCA color types leading up to the ctc-16, I'm not sure what rev that was in your link, but it's not a 16, for the following, when they came out with the 16, the voltage doubler was removed when they added the degaussing coil circuit, also, some of the tube types dont match up with what is in the set as shown.

There were about 6 schematics in the boxcarcabin link.... easy to miss unless you zoom out and scroll... The CTC16 a in 2 variants is there near the bottom.

On that RCA schematic it's C118a then, ( I did not see it at the bottom)
I still prefer the Sams, cause it's easier to see, and has much more info, like waveforms.

If C118A, then I would expect a sawtooth and that ripple magnitude sounds about right. That sawtooth is just the capacitor discharging as load current is drawn and then recovering as the rectified AC input waveform recharges it. The ripple is high here since this is the first filter capacitor.

For checking tubes, substitution is always your best bet. It would make sense to have on hand spares for most of the tubes in that set. Drugstore testers were more about tube sales than thorough tube testing.. for a really good test, a mutual conductance type tester is always best, but not really worth getting until you're surrounded by tube equipment needing repair. If you want to find one locally, figure out where audiophile, ham radio enthusiasts, or antique radio collectors hang out, you'll probably be able to borrow one, or at least bring your tubes to someone to check.

It's alive!!! Ha ha ha ha ha ha ha ha ha !
 

I have COLOR!!!

https://imgur.com/a/ttpXARP


I still have much work to do... yes,

my color / bar generator is broken , so I took a VCR and tapped in a video at the first video amp and that is what i got.

the yoke has been off, so nothing is adjusted, all out of focus , but this is a BIG step forward! :D:banana:

This is probably going to take a LOOONG time to get working correctly. :(
not that I did not expect this, after it sitting in storage for so long :/
I still can't get anything through the tuner/if yet , no telltale HISS from the speaker, ( but there is a faint hum/ hiss heard ) .

60% of filter (electrolytics) replaced,
when turned on I do get HV and raster, and when I tap in video to the point mentioned at 1st video anp , I get a fuzzy video ( levels are prob not correct impedance for the tap ) but I see the video with color, and have vert / horz lock.

Trying to find a tube tester.

Am i going to have to end up checking every resistor / cap in this thing? T_T
Well if that is what it takes...

Try wiggling the IF tubes. If the first IF gives pix noise and or sound noise then the problem is in the tuner if not it is in or before the lowest IF tube number that gives noise when wiggled. Another possibility is the AGC is missadjusted or broken....In that era of RCA the AGC checks the sync level in the video signal every horizontal pulse and adjusts the tuner and IF gain (by changing the grid bias of the tuner and IF tubes) to hold the video level constant.... the AGC control should be able to take the set from blank raster with no signal passing through to normal signal then on to excessive overdriven video that won't sync.... circuit failure can hold it in an exterme state.

i will prob start poking around the IF section once the rest of the caps are replaced and tubes tested.
FYI, this is the video i was injecting, https://imgur.com/a/z4Sh5ZD
taken by crappy cellphone camera on a tiny 3 inch color analog monitor i have.
I'm just very happy the color works on my CTC :)

It would probably be much more productive to send an actual image rather than a colored raster. You can check if your color, focus, sweep linearity, etc are good. That blue field you sent it will hide many issues that might be good to know about now.

Also (if you haven't already done this) before you go running it for more than 10 min stints it would be wise to go through the sam's horizontal setup procedure (especially checking and minimizing horizontal output cathode current)...These sets can cook their own flybacks really easy if everything ain't just right,

It's true that I do not have it on very long when I do turn it on, and I have not yet run the horizontal setup procedure , as it says “ tune in a TV station and set controls for normal operation” However, this can prob, be done just as well with the injected video.
As for not being able to tune anything in yet, ( this is most likely due to entropy, for it used to before )
After all electrolytics are replaced, and I have confirmed that the B+ on all the voltage dividers is OK, and tubes check OK, I will probably go over the whole thing end to end and measure tube voltages (K/G/P) .
which may, hopefully give clues to problem areas.

Well, that is not good... it looks like my AGC circuit is messed up.
No doubt its the reason I can't tune in anything...
https://imgur.com/a/NsW2dox
As far as I can see, R37 is the plate bias source, this circuit id a bit weird ) could also be leaky caps.. IDK.

Something is not right... 9v is way too low...
I am getting a very good strong horz pulse there though.
i will have more time to play with it this weekend.

The AGC circuit is a feedback circuit. This means that the 9 volts at the plate does not necessarily mean anything is wrong with the AGC circuit itself. It may be getting an incorrect detected video signal at the grid due to some other reason (like a dead IF) and trying to correct it by changing the AGC voltage. You need to check the detected video for starters. If it's missing, check and/or replace the AGC tube. And, you may be right that some component is bad. Check all the voltages in this area. Check resistor values wherever voltages are way off. Further trouble shooting could involve breaking the feedback loop by connecting an adjustable bias to the AGC line, as you would for aligning the IF. If video is missing or wrong amplitude and you can't get it by manually setting AGC bias, there is something dead in the IF or tuner.

IF problem?
 

I did try to “ wiggle” the IF tubes, and I did hear a crackle in the speaker as I did on all of them.
However, at this point, I have NOT been able to test any of the tubes yet, :( but I do know all bias voltage is there ( within 10% )
did a quick reading of plate voltage on ACG tube, did not match SAMS, ( as shown in other post )
suspect 1st if bias is not right as well, I'm prob stuck till I can get these RF tubes tested :/

OK, i think i found someone with a tube tester rather close by, I jst have not been able to get my hands on it yet. :(
Poking around the IF section, i did spot something a bit disturbing, https://imgur.com/hVmgorU

why is the bottom part of that NPO cap uncovered? did they not see that when they built it? It cant have been good to have that bit of its innards exposed all these years. :/

Looking a bit closer at the schematic ( just guessing ) that cap is a critical part , since it was a 5% and was part of the adjacent sound reject, so if it degraded because of being exposed and de-tuned the circuit... perhaps it may do what I'm seeing, not being able to tune in anything...

I've seen ceramics with that exposed bottom before...I believe it is probably done in the factory for a purpose.

If it doesn't leak current under voltage, and if reasonably close to rated capacitance it should be fine.

I saw many brand new ceramics like that when I worked at Zenith, that obviously met specs. Never had time to investigate why they were like that, but now I wonder if it was a way to tune them to within 5% in the capacitor factory by etching away some of the metal.
EDIT: or, of course, it could be unintentional but acceptable.

Disconnect and check that 150K and 180K resistors next to the 2nd IF tube, they're usually bad

There lies the headache, it's easy to check the value of a cap with any given digital meter, but leakage is tricky w/o a costly meter or some vintage tester, :/ unless, I go and build the circuit seen here... http://www.angelfire.com/electronic/...ting_caps.html
I do not intend to test electrolytic capacitors with it, so with 400v or more, if the cap under test is good, the reading for leakage should be 0...

R48/r50...
yeah, i can see how that can mess things up, if they were bad.

As mentioned, I'm waiting till i hear from the guy here who has the tube tester, before I dive deeper into the IF section.

as a side note, i DO HEAR a audible POP, each time I change channel on the VHF, so SOMETHING is getting through.

So, I gather, tubes aside... that there is a higher probability that the old carbon core resistors could be out of tolerance than the ceramic disc caps, ( not that it can't be both :/ ) Which kinda makes sense, I had my Sansui 9090 go from working to non-working sitting in the same shed as the CTC, for a few years and had to replace several resistors on it to get it to come back up.

edit---
good thing to note, as I was poking around for info, I should stick with Carbon Composition Resistors if i do replace any, ( in the IF )
"Film Resistors-their frequency response is much worse due to the inductance and capacitance caused by the resistive path cut into the film." :o

40 mfd capacitors are available. Newark lists no fewer than 15 of them. I doubt the value is very critical.

The carbon comps are moisture sensitive...Storing them in a humid environment is pretty much the best way to force them to drift...Short of storing your set underwater.

The film types probably won't make a huge difference in the IF.

the carbon core ones i am seeing on Mouser are all 5% so I'm sure they will be better than the 10% that was in there.
And yes, it was stored in a shed outside, in central Texas, where it got as hot as 110f, cold as 18f and quite humid, but it was covered and protected.
So, with all that, I'll start with looking at the resistors in the If.

Oh yes, I definitely have some flaky resistors... I'm finding some wide open and others beyond 20% (some OK ) , will put some new ones in this weekend and see what happens.

The CTC16X is worth the effort. I had one and it made about the nicest picture of all my 60s'-era RCA sets, including a CTC38.

pissed
 

:dammit::dammit::dammit::dammit::dammit::dammit::d ammit::dammit:

Dammit dammit dammit!!!! BLOODY HELL!
Just when I get the IF section semi working..

I SEE snow on the screen ( with color ) I hear it in the speaker.

I go to hook something to tune in, click to the right channel, fine tune, I hear audio and POP, i lose raster...

WTF??.

quick check...

yes still have HV,, all tubes still lit, but something smells hot …

close look.
:saywhat:
i lost 970v boost... :(
https://imgur.com/fZYxnRF
https://imgur.com/ZNpZOcw
why did it have to choose THAT MOMENT to fry?!?

Check the caps that filter the boost for shorts also check the line for shorts (such as tin whiskers on pots, insulation breakdown and such). Something caused that resistor to burn up like that.

Also, it may be wise to get a new boost diode. I've seen them fail more than once and what killed that resistor may have damaged the diode too...Radio Shack carries a 2A 1.5KV PIV diode that if you place 2 in series makes for a really rugged boost rect. Failing that similar specked diodes off the net will work.

My first roundy I came at the problem from the opposite direction. After fighting to get HV, and having sound, but no raster and chasing voltages I finally found my cooked boost rect...The hilarious part was that aside from no color and shrunken raster from dying caps the darn thing worked great on varic power up for a few secs before dying, and I never retested tube damper after power-up so after driving my self batty trying to get HV for a couple of months, and giving up I found the problem robbing the tube for another working set that had an intermittent damper arc.

a tin whisker like https://imgur.com/eUeytX9 that.. :(
so i guess that pot is shot..

I'm not sure if I'm looking at a whisker too thin to see, a really fat whisker or a normal part of the pot rotor.


The pot is not necessarily dead. They can be serviced. Verify the short on the boost, unsolder the pot leads and verify the short in the pot...If short is still present (and not the fault of the pot being set to min or max) on disconnected pot then unmount the pot, pry the tabs from the back cover that wrap around the front up till you can take the metal back cover off, verify the whiskers and what they are growing from, sand the growth surface lightly with very fine sandpaper till whickers are gone and surface is clean and shiny, remove metal particles with contact cleaner double check resistances are normal and reassemble.

If disconnecting the pot does not show the pot shorted but boost is still shorted keep tracing that short on the boost line.