CTC-16 Restoration

[Yamamaya42]

Originally Posted by Zsuttle

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

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.

[Zsuttle]

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

[Yamamaya42]

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!

[Zsuttle]

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

[Zsuttle]

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.

20240819_174142.jpg
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.

[Yamamaya42]

Originally Posted by Zsuttle

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.

[Yamamaya42]

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. :/

[old_coot88]

Originally Posted by Zsuttle

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.

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.

[Zsuttle]

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.

[Yamamaya42]

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.

[damen]

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.

[Zsuttle]

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?

[Zsuttle]

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

[damen]

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.

[Yamamaya42]

Originally Posted by Zsuttle

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

depends on the type of lat magnet you have.

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

this is mine.