View Full Version : My new CTC-15

09-16-2017, 06:37 PM
Got this CTC-15 today for only $32. It had the original tube, but it was replaced because I wanted the rare earth phosphor.

09-16-2017, 08:30 PM
Sweet! And inexpensive too! :thmbsp:

09-16-2017, 08:48 PM
Good lookin' set!

09-17-2017, 02:22 AM
Finally fired up the CTC-15. Check out that incredible picture!

09-17-2017, 03:08 AM

09-17-2017, 11:34 AM
Nice! I've been after something similar for a few months now. I'm still convinced no one in my neck of the woods had color until the solid state era......

also that Futurama subtitle is hilarious :D

09-17-2017, 01:01 PM
Great find. As you're probably already aware, the two ground stakes on the far right end of the chroma board exist in two states: either cracked or gonna crack soon. They need to be re-flowed as a matter of course on every CTC-12, '15, '16, '17 and '25.

When they fail, the heaters on the 6GU7s go out, causing the plate voltage to rise. Since the plates are DC-coupled to the CRT grids, this makes the CRT beam current go nuts, lugging down the HV supply. Pic blooms, loses focus and fades out.

Tom S
09-18-2017, 08:31 AM
Very nice set. If you have your other tube I'm interested. Have a CTC11 I would like to improve. Thanks

09-18-2017, 03:02 PM
Had to trade the old tube for the new one.

09-18-2017, 08:45 PM
Well, I'm fighting my first battle with the CTC-15 already. The CRT keeps randomly loosing filament voltage. I took the back off, inspected the socket and CRT base, and put a drop of Deoxit on the filament pins, and that fixed it. I put the back cover back on, and it's out again.

PROBLEM SOLVED. Had to heat up the CRT pins.

09-19-2017, 09:40 AM
Heck, take it back for a warranty claim on the CRT. :D

Looks nice...

09-19-2017, 01:02 PM
This is becoming the most problematic TV I've ever owned. I had to fix the CRT filament again last night, and I decided to just leave it away from the wall with the cover off. It was working perfectly fine when I went to bed, and when I got up today, I had no blue, no red, and a whole lotta green. I tried swtching the 6GU7's around, and after that I got no green, and whole lotta purple. So then I go find another 6GU7, and put it in the G-Y/blanker tube socket, and the green was still dead. I'm at a loss.

Electronic M
09-19-2017, 01:17 PM
Has the solder ground stakes/traces on the chroma board been reflowed?..If not then you will want to do that.

09-19-2017, 05:33 PM
New tubes, clean sockets, solid solder joints, FTW.

09-19-2017, 05:51 PM

09-19-2017, 06:52 PM
The ground steaks didn't look bad, but I reflowed them anyway. I replaced the 6GY6's, 6GU7's, and 6GH8's, the 6EW8*, and the 6JE6 horizontal output.

*I had to substitute a 6GM6 for the 6EW6, the substitution book says it's fine, and it works.

09-19-2017, 11:18 PM
Are you sure the contacts in the crt plug aren't just loosening up when it gets warm?

09-19-2017, 11:34 PM
The pin(s) on the CRT for the filament were not making good contact with the wires inside.

Speaking of which, it just broke again.

09-20-2017, 11:34 AM
Reflowing CRT pins is not difficult but I hope you're not trying do it with a low-wattage pencil type iron. Use a Weller 100 watt gun. The tips tend to get concave on both sides of the original chisel-point and this is perfect for maximizing contact area. Place your tip as close to the base as possible and feed solder into the hole. It should flow toward the heat spot and full up the pin.

I successfully replaced a broken-apart CRT base on my test jig CRT and its working just fine. I am also working on a CTC15 chassis, that needs lots of solder-pencil work as standard procedure. It also has a shorted flyback (not burned up), for which I have a NOS RCA#113382 replacement that was made in Mexico.

11-07-2017, 08:05 AM
I just snagged a CTC-15 for $2 at an auction. It's my first foray into the roundie world. The good: It's got a 21GVP22 with a date code of 52nd week of 1971. Absolutely no sign of cataracts! It's also had a new flyback transformer installed (probably when the picture tube was). It's very clean inside with just the finest layer of dust. The flyback and picture tube look like they just came out of the box. The bad: I powered it up slowly on a variac. I've got audio and raster but there's high voltage dancing all around the outside of the picture tube to the chassis surrounding the tube. I haven't left it powered up past the point that the arcing starts. The screen just begins to light up before I kill the power as the arcing starts. I'm guessing I've got ground issues. Haven't dug into it more than that. Anybody got any ideas? I'm new to the roundies but have been around tube gear like radios, jukeboxes and amplifiers for many years.

11-07-2017, 08:33 AM
Here is the CTC-15 after I got it home and where I found it. I would have grabbed the two B&W Zeniths too but, I just do not have the room.

11-07-2017, 10:02 AM
...The bad: I powered it up slowly on a variac. I've got audio and raster but there's high voltage dancing all around the outside of the picture tube to the chassis surrounding the tube. I haven't left it powered up past the point that the arcing starts. The screen just begins to light up before I kill the power as the arcing starts. I'm guessing I've got ground issues. ...

Probably just lost the dag ground (the black conductive coating on the outside of the CRT). Should be easy to find.

11-07-2017, 11:16 AM
I agree about the dag. There should be a spring hanging on the bottom of the CRT to ground the dag. If that is missing, weird stuff will happen.

Maybe you should make your own thread instead of hi-jacking mine.

Electronic M
11-07-2017, 12:14 PM
If the arcing is not coming from the HV connector the ground spring (or the connection between the front and chassis), or possibly the dag coating on the CRT is missing and or bad. If the arcing comes from the HV connector on the CRT, discharge the HV, then clean the snot out of the connector/wire and the ~2-4" surrounding the connection on the CRT.

11-07-2017, 12:28 PM
Well, I wasn't trying to hi-jack anything. I simply saw you had recently gotten a CTC-15 and thought perhaps we could exchange information. I was obviously wrong. Sorry you feel that way. Thanks for being so friendly. NOT!

To those of you who were being helpful without being facetious, Thank you! Have A Nice Day!!! :)

11-07-2017, 12:48 PM
I apologize if I came of as rude, I would be more than happy to answer any questions about your set. I had just woken up when I wrote that comment. This is the spring for the aquadag you should inspect. If it's not there, you'll have arcing, and the screen geometry will be distorted.

11-07-2017, 01:03 PM
It's all good. I'm pretty thick skinned. I just thought, "dang, I was just gonna ask a quick question and go." I thought who better to ask than somebody who is going through the same chassis at about the same time. Thanks for the reply.

Yes, the spring is on there and the dag doesn't look like it's gone. However, I haven't cleaned anything yet and the set wasn't exactly stored in the greatest surroundings. It was way back in the pitch black darkness of a musty old building. The spring may be slightly rusty/crusty. Thanks again for the tip. I'll look at it soon and see what happens. It sure would be nice if there's not much more than that wrong with it. As I said, I'm not really up on my TV skills. I've stuck primarily to radios, jukeboxes and lots of amplifiers of all sorts. It looks like I'm going to have to do a little refresher. Thanks again!

11-07-2017, 01:13 PM
Pictures of the inside, and the general area where it's arcing would help. Whenever I get a new set, standard practice for me is to check every tube, and clean every tube socket, control pot and the tuner with a spritzing of Deoxit. Also, as you may know, these sets suffer from cold solder joints. It's imperative to reflow all the ground stakes and scrutinize all the other joints on the board for cracks.

11-07-2017, 01:49 PM
Well, it's arcing all around the diameter of the tube where the metal frame surrounding the tube is. It arcs in that 1/4" gap. It sizzles after the set has been on about 5-10 seconds. As the HV comes up and the CRT comes on it intensifies. The dag coating sounds like the issue. I'll try that when I get the chance to work on it.

As far as everything else goes, what you listed is where I'm headed to. I've already tested tubes. A couple are marginal. I need to go through my stash and find replacements. I plan to give it the thorough going over when I get the free time to do so. As far as soldering joints, a long departed repairman I knew many years ago told me "95% of the repairs I've made in my life were just busted solder joints." I've found that and, with the passage of time, capacitors to be the majority case as well.

11-15-2017, 12:31 PM
There are never too many roundie threads here. I enjoy all of them because I do repairs for other collectors. Lots of info is shared.

I have two CTC12 chassis with similar issues to all the post CTC11-chassis TVs, including the '15's.

If you hone your skills on this era of color set, you will be able to extend that to the real early color TV's, which are a bit more of a challenge, even for the advanced guys that post them.