CTC-5 Service Info Sought

[bgadow]

My lingering problem has been that I can get a stable picture but it will be somewhat washed-out; hv will measure in the 17-18kv range. I can detune the horiz hold and get the hv up but the picture will be shifted to one side, along with expected color defects. I previously did a lot of back and forth between the 2 adjustments but never found a happy medium. Your experience encourages me to attempt it again. There is a ton of travel in that horiz hold; it is easy to go too far, throwing the frequency much too low and killing the raster (and trying to kill the H.O. tube!) I've yet to order new caps; I'll experiment once more before I do.

[bgadow]

After months of on-and-off work I've decided the Whitby is good enough for now. Here is what I did since my last update:

I replaced all the low value (mica, etc) caps on the horiz. osc. board along with some resistors that were just a little off. I was eventually able to get the oscillator waveform to look like the picture. While I was at it I did the contrast control mod; funny, in another thread old tv nut mentioned doing the mod according to the magazine article and he ended up with the travel being backwards. Well, I purposely wired it the opposite of the article-and I ended up backwards, too! Not sure how or where it got messed up both times, but not a big deal.

I was able to gain a lot of stability; my lingering problem was high voltage that was too low. The best I could get with brightness turned down was 18.5kv. I looked at the waveform going in to the HO tube and found the peak was very rounded, not sharp as pictured in Sams. After the above recap this was also corrected but the HV did not improve. I spent a lot of time measuring currents and voltages at the HO and regulator and the only thing that was out of spec was the drive voltage to the HO. It should be 190v but instead was running 175+. The resistors in that circuit test good and the caps are new. I finally decided not to fight it anymore as the set performs pretty well as-is. I went ahead and did the setup-I was surprised that the purity looked fine. Yeah, I know, in the first photo posted below there is some impurity in the corner-only shows up on the red. That is one of a few problems I'll save for some other day. (likely some other year!) There is some color smearing, for one. I guess that term is correct. Delay line? Or just something off kilter on the color board? And vertical lines have a waviness-not a crawl, they stay put. I'm not going to let this bother me as this is about as good as this set has been since I bought it, and I consider it an ongoing project. With time my abilities, hopefully, will improve, and I'll feel more confident when it comes to tackling these other problems. For now I'll just kick back and enjoy the show.

[zenithfan1]

Looks nice! Good job Bryan. I have a long way to go on mine.

[jeyurkon]

Bryan, I just read all of the posts. About the mica caps. With the arrow pointing to the right, if the upper left dot is black then it is mica. If it is silver, then it is paper.

Any chance that when you tried to kill the HO tube that you did hurt it? If you managed to get it just a bit gassy could the grid start to conduct once the drive gets near it's peak and clip the waveform?

I'm not sure what your horizontal oscillator stage looks like. If it's a cathode coupled multivibrator, then perhaps that tube is just weak. I must be showing my ignorance here. Chelsea, my cat, just looked at the computer screen, snorted, and left.

Enough of my weird theories. I think your set's looking pretty good!
John

[Tony V]

Looks good from here Bryan!
-Tony

[Ampico-kid]

Hey Bryan;

Coming from someone who just recently went through a lot of the same issues with my CTC5, I'd say you're doing GREAT. It's really coming along and even now looks terrific!! Take a break, sit back and enjoy it for a while, give yourself a chance to think about it, and then pick off the remaining issues one at a time.

It's really nice to see these old relics from the past coming back to life once again. You should feel proud that you're helping to make that happen. Keep up the good work !!!

Bob

[Tomcomm]

Brian.....Looks like you're getting there, Full raster and good color rendition. Seems you need to do some fine tuning in the baseband video portion to sharpen things up. If you have a good scope you can use the Digital Video Essentials DVD and a VCR modulator to analyse and tweak all the video system. If you are adventurous you could make an external video input to replace the CTC12's video detector output and bypass the RF/IF system until you get the baseband as good as its going to get. This is what I did on the 21CT55. Lotsa Luck.............Tom

[bgadow]

Thanks guys! Tom, I was thinking about that DVD-have heard it referenced once or twice. I need to pick one up. My Sencore Color King does okay but some sets (including this one) just don't like it. I can't get a dot pattern to lock in. The next time I tear into this I think I'll swap out the low value caps on the AGC board and also do some good probing of the color circuit. John, good tip about those micas, I'll have to write that down. I swapped the HO tube with another without any change, but then the other one (though it looks like new) isn't NOS. I would just go and buy one but this summer I bought a truckload of tubes, all sitting up in the attic now. There is a good chance that I have one NOS in that pile, and I will try another swap. The worst damage I might have done was once, during this process, forgetting to put the horiz osc tube back in the socket. I then stood there with a dumb look on my face trying to figure out why the HO current was pegging the needle!

[radio63]

Great work Bryan!! I love the saturated color stills of the "Lucy Show" titles. This makes me want to go back and finish up my Westcott CTC-5 that has new capacitors throughout but still needs a bit more work. Enjoy it for a while, you deserve it.

Gilbert

[roundscreen]

Originally Posted by bgadow

After months of on-and-off work I've decided the Whitby is good enough for now. Here is what I did since my last update:

I replaced all the low value (mica, etc) caps on the horiz. osc. board along with some resistors that were just a little off. I was eventually able to get the oscillator waveform to look like the picture. While I was at it I did the contrast control mod; funny, in another thread old tv nut mentioned doing the mod according to the magazine article and he ended up with the travel being backwards. Well, I purposely wired it the opposite of the article-and I ended up backwards, too! Not sure how or where it got messed up both times, but not a big deal.

I was able to gain a lot of stability; my lingering problem was high voltage that was too low. The best I could get with brightness turned down was 18.5kv. I looked at the waveform going in to the HO tube and found the peak was very rounded, not sharp as pictured in Sams. After the above recap this was also corrected but the HV did not improve. I spent a lot of time measuring currents and voltages at the HO and regulator and the only thing that was out of spec was the drive voltage to the HO. It should be 190v but instead was running 175+. The resistors in that circuit test good and the caps are new. I finally decided not to fight it anymore as the set performs pretty well as-is. I went ahead and did the setup-I was surprised that the purity looked fine. Yeah, I know, in the first photo posted below there is some impurity in the corner-only shows up on the red. That is one of a few problems I'll save for some other day. (likely some other year!) There is some color smearing, for one. I guess that term is correct. Delay line? Or just something off kilter on the color board? And vertical lines have a waviness-not a crawl, they stay put. I'm not going to let this bother me as this is about as good as this set has been since I bought it, and I consider it an ongoing project. With time my abilities, hopefully, will improve, and I'll feel more confident when it comes to tackling these other problems. For now I'll just kick back and enjoy the show.

I think the picture looks good on your set and I like the red,green and blue credit shots you took.
No horizontal drive control is used in the ctc five. Instead, R138 is selected within the limits of 82k and 150k to give proper drive. A convenient way of finding this best value is to remove one end of the original resistor and try various values in series with it until the highest value is found that will not cause drive marks. {Quote from a book I have}
I had the same problem with the ghost in the video and color but do not recall what the fix was. I think it had something to do with the IF or the tuner .The next time I run one of the ctc 5's I will look at the chassis and see if I can find the parts I replaced and or what I did to it.
Ed

[old_tv_nut]

As long as you realize it's just a guess, let me say that the luminance response looks OK, and therefore the delay line is probably OK. That says its some kind of chroma smear, but I can't guess from the look of it if it's due to tuner, IF, or chroma bandpass alignment. Did you replace any small-value caps on the chroma board (10's or 100's of mmf)? Anything associated with the chroma transformers could require re-alignment.

Thanks for keeping us up on your progress!

[bgadow]

Ed, good tip on the drive resistor, I didn't come across that anywhere in my reading. I'll add that to my "to-do" list.

Wayne, the only thing I recall ever doing on the chroma board was replace any "paper" caps. This set has produced a color picture since the day I found it so I never saw the need to go monkeying with it. But I do need to figure it out someday. Most noticeable when you have a person standing in front of a fairly bright yellow background-their face will end up the same color yellow. I also need to study up on the proper setting of the ACC & matrix controls. Right now they are both cranked down because that is what gave me the best picture. Yep, more for the "to-do" list!

[Findm-Keepm]

Bryan,

After looking for it for another post, I just found my 1955-1966 RCA field service guide that covers the CTC-5 and others. There were a significant number of production changes that affect the CTC-5 chassis. The Field Service guide shows the Whitby as being either a CTC-5N or CTC-5P chassis, different in many ways than the CTC-5 and 5A. Two components in the oscillator are listed as changing value - C605 (at terminal "B" of the PW600 circuit board, where the oscillator tube is located) changed from 12pF to 5pF. R603 (at the sine coil) changed from an 82K to a 100K ohm. The component designations are from the RCA schematic, not Sams. These are production changes, not differences between the 5/A and the 5N/P chassis, and may be improvements that affect what you've been facing. I can loan you the Field Service Guide if you want to tear back into your (BEAUTIFUL) set someday - just PM me, I probably already have your address in my folder.

Cheers,

[roundscreen]

Here is a picture of the horz osc board. This should make it easier for you to find the R138 .
Ed