CTC-16 Restoration
 

I've been slowly working my way through a CTC-16 that I picked up several weeks ago. The picture tube tested strongly, and all but one of the tubes were RCA tubes. All but a handful of tubes checked out and were replaced. I replaced the electrolytics as 2 of the 3 cans had a fairly high ESR. There was a corroded wire that was replaced on the topside of one of the boards.

I had excessive HOT current, and was able to bring it within spec by replacing several out of spec caps in that section. I was then able to adjust it to spec. HV is still on the low side (20kV) and have yet to look into that.

I put a test pattern generator on channel 4, and was able to get a somewhat fuzzy attempt at a colorbar. I believe it to be a chroma issue, but have not looked into it other than verifying the presence of the chroma oscillator at the chroma synce phase detector input.

Any advice is appreciated in troubleshooting this set

Your color oscillator is unlocked, but it's not time to worry about that now. First turn the color down and work on getting a good black and white image. It looks like the picture is out of focus, probably related to whatever is causing the low HV.

I was able to work on the chassis tonight and found several more out of spec resistors in and around the horizontal area as well as many of the 5% cathode resistors. After doing so, I was able to get my HV to max out at around 24.5kV and lowered it back to 24kV.
I'm still unable to focus anything. The focus control does nothing noticeable when turned. Both the HV rectifier and the Focus rectifier are new drop in solid state replacements.

Just to check, the boost voltage just provides screen voltages?

How about using your HV meter to measure the focus voltage, starting at the CRT and working back?

As a test, pull the focus rectifier while the set is on. If the screen stays lighted it usually means the 47 or 66 meg focus resistor is bad. A bad resistor can cause the coil to have little if any effect on the focus. If the screen goes dark as soon as the tube is pulled, the resistor is probably okay.

Ok, here's what I've checked. The focus output to the CRT is 4.3kV, which doesn't change with the focus adjustment. Junction of the 66meg resistor checks out to be 4.56kV.

I pulled the focus rectifier was running, the screen stayed lit. I checked the 66meg resistor, it was reading 64.5meg with a megger at 1500V.

Also, horizontal position pot is shot. Track measures 10ohms, but the wiper is intermittent. Cleaning didn't help. Any suggestions on a replacement? I can find ones rated up to 500V, but nothing over that

The RCA part number for the centering control is 113381. The ETF has them, also check with Moyers and Talon Electronics. Check and see if the focus voltage varies with the CRT socket disconnected when you adjust the coil.

Thanks for the PN, for some reason I had another number that wasn't showing up anywhere. Ordered the part.

Focus at the socket was reading 4.25kV with the tube disconnected, didn't change when the control was adjusted.

For my sake, the focus control should only turn about a turn?

The 113381 is a new number RCA used to replace several similar controls. It also replaces the vertical centering control when you remove the plastic shaft it comes with. The focus coil should turn maybe a dozen turns running the coils slug in and out. Check and be sure the slug is moving, I've had them detach from the shaft. Also make sure none of the wires have broken off the coils terminals because it does move around when the shaft is turned. If you have the socket unplugged from the CRT, check and see if you get any voltage on the focus pin on the CRT base.

Well that'll about do it. Focus control was jammed, unjammed it and now I'm able to properly focus. Now I just need to narrow out my color issues. Not entirely sure where to start. Is there a nice guide for proper adjustment of a TV from scratch? I know a lot of service manuals cover purity, convergence, cutoff, etc. Didn't see that in the SAMs for the CTC-16s

Also intresting note, the red screen control really drives up the horizontal output current. The blue and green screen controls don't do that. Is that entirely normal?

Could that be because the red phosphorus is less sensitive and needs more drive to illuminate it?

Could be with the phosphorus, I'm wouldn't be the one to know.

I was able to scope out the waveforms on the schematic in the surrounding areas. Maybe someone can catch something I'm not seeing.

Chroma sync phase detector:
Attachment 206803

Attachment 206804

Attachment 206805

Chroma bandpass amp:
Attachment 206806

Color Killer:
Attachment 206807

Burst amplifier:
Attachment 206808

Edit:
Photos don't seem to be appearing for me, if anyone else can let me know if they see them

Not able to seen the photos directly; I need to click in the "link", and input again the VK credentials, for each one.
LATE EDIT: after that, all the photos appeared in the post.

What is the color problem you are trying to chase? Color still unlocked?

I don't have a reference for the color killer and burst amp waveforms, but I would have expected a pulse waveform that is more clearly coincident with the burst, while this seems to be triangular with its peak during active video. What happens to the timing if you move the horizontal hold a bit clockwise or counter clockwise?

Color is unlocked, the waveforms I took were the waveforms called out on the SAMs. Got it from the ETF website. A paper copy is still on order as some things are difficult to read.

Horizontal hold will shift the whole image sideways either direction before losing the horizontal lock. It didn't appear to make any difference on the chroma oscillator. I'm pulling the chroma oscillator from the cathode of the chroma sync phase detector V19

are these taken with a x10 probe and the scope not set for it? cause the SAMS has the beat pulses at the sync phase det at 90v, but it's WAY below that in your pic.

Yeah, good catch. 10X probe, forgot to plug it on the scope. Pk to Pk, 108v on the beat pulses. I was more checking for correct waveforms over voltages on my initial check

then you should be able to try the "color afc alignment" under miscellaneous adjustments in the SAMS, If it works, then all is well, but if it fails after a few tries, like it did on my CTC-16XL, then you have faults to hunt down!:tears:

Well, another siezed coil, I was able to adjust everything and somewhat get a colorbar. There are some minor adjustments that need to be made and some major color adjustments.


The screen has a heck of a flicker, almost like seeing a series of images versus a constant picture. It's as if the frame rate was too slow

I went through and replaced the rest of the maroon caps after another two had issues. Was able to get a much more solid picture, and eliminated the flickering on the screen. I finally took care of the cateract, boy what a difference. The glue separated without much effort and came off as one big sheet.

Attachment 206810
How long should the horizontal take to settle in? The oscillator is noticeably drifting, enough to require readjusting every 30 seconds or so. It's not hard to get a lock, just hard to keep the lock.

Yes, the caps next to the Y-amps get COOKED! and I had to replace mine.

I rarely have to adjust my horizontal hold, perhaps once in a blue moon when turned on, then it stays locked, there is a voltage dependent resistor in the power line to the horizontal hold circuit, if that is worn it could cause problems, but replacements are rather unobtainium. :(

Intresting, the CTC-16 does not have the VDR, but the 16XL & CTC-20 does.
https://www.ebay.com/itm/395361002948
This part, along with a change of the size of the 1w resistor, 150k vs 120k (82k), shown on SAMS.
If you have the CTC-16, not sure how to get it more stable. :/

Weak/drifty horz lock is almost always due to the phasing diode (the 3-legged dual diode) located near the oscillator. Surprizing nobody's mentioned it.

I should just be able to replace it with some schottkeys right?
Also, wanted to get some questions answered, what's with C82 having a 1.5kV rating? It's seeing like max, 200V?

Are there any known problems with the mica or ceramic caps in these sets. I figure the ceramics should be good, but I know mica can have issues longterm with high voltage drops accross them.

Ceramic caps almost never go bad, they can, but it's rare.
As for C82, it's being hit with very strong horz pulses on top of the dc voltage, thus the 1.5k rating.
And yes, there are many small diodes to chose from as replacement.

RCA sent out a service tip about a modification to the sets without the VDR. Resistor R525, the 1000 ohm off of pin 5 of the 6CG7, is changed to a 560 ohm and R521, the 22k off of the horizontal hold control is lifted from ground and returned to pin 5 of the 6CG7. This change was made at the factory starting with the CTC-19 and 20 I think.

Looked at the CTC-20 schematic, I see what you mean. I'll make the mod as well as changing the phase detector. That gets me thinking, is there anywhere where changes like this are listed?

Also, does anyone have a PDF copy of the RCA CTC-16 service manual? I've found some paper copies, but they don't list my model. My model is a KF 593M. Not sure the difference between the different versions other than phono, remote, etc.

I need to know where on the tube to position the lateral magnet, as well as a few other things. After I fix the final few issues, I'll head onto purity and convergence

Your KF-593 was one of the "custom collection" sets (model number began with a K). The RCA index lists it with the service information being available on a limited basis, special order only.

depends on the type of lat magnet you have.

http://suzaku.live-evil.org/0606221959(1).jpg

this is mine.

Hi to all,
Hi Zsuttle,

SAMS 20 page manual here, 2.9Mb pdf :
https://www.earlytelevision.org/pdf/...ams-0736-4.pdf

The CTC-16X is also available.

The ETF Museum database is the "go-to" place for vintage B&W & color TV data.
Color TVs by Brand :

https://www.earlytelevision.org/tv_s...ams_color.html

Hope this helps,

Best Regards
jhalphen
Paris/France

Thanks for the info, but I've been using this SAMS from their site, I was looking for the RCA service manual. The RCA manual has a little bit more information about adjusting the set, I was able to buy one online.

Onto purity and convergence. Does anyone reccomend a good lubricant for the convergence pots? I've got a couple that are stiff, and was able to get a few moving with some contact cleaner, but they're still harder to turn than some of the other pots on the board. I was thinking dielectric grease, or I've seen F5 fader lube/cleaner reccomended for other applications.

This is par for the course with the pots on the convergence PCB,they always tend to be hard to turn no matter what, as they are 2W wire type pots, and I have never seen one that was not stiff, and It's good that they are, cause you dont want them to move once set.
I would leave them as is.

If convergence are ok, and not have bad contacts, is possible to leave as-is.
But once I had bad contact issues with the a convergence board that makes the vertical jumps or jitter. Cleaning the pots solved the problem.

I don't have much to add other than I'm glad to see someone saved this set. I was tempted, but I just don't have the room. Best of luck dialing it in :)