RCA CTC-36 Woes

[Kamakiri]

Was watching my beautiful CTC-36 portable one day about 2 months ago, and (as seems to happen to me on a regular basis with various sets) heard a loud POP, and the set lost all color sync.....the color went to bars of color rapidly flipping vertically, while the actual picture was still locked in, in black and white.

After my Portacolor debacle over the last few days, I needed to get some vindication, so I opened up the RCA. After replacing a .01 mfd ceramic capacitor on the board where the color drive controls are located, the color locked in nicely, but I'm getting color retrace lines on the screen.

Picture is purposely washed out by the controls to give you a better idea of what I've got. Picture itself is very slightly jittery, but locked in solid. Just a tiny tiny amount of jitter, just enough to make you angry

Ideas?

[ctc17]

First thing I would do is run it with the back off and flex the boards with a stick and look for a change. Could be a cracked solder or poor connection somewhere.
Could be a retrace issue or the crt is being overdriven. A ground or component failed in the screen, drive or video circuits.

Does it seem much brighter that before?

Im sure I have the service data on that chassis and can dig it out for a date with the scanner.

[Kamakiri]

Brightness, contrast, etc, are all about the same. There is a remote possibility that I might have flexed something in the convergence board when I pulled the main chassis, as it was a tight squeeze getting the chassis over the top of the board to pull it out. I'll give that a try this evening. Thanks!

[dieseljeep]

Originally Posted by Kamakiri

Brightness, contrast, etc, are all about the same. There is a remote possibility that I might have flexed something in the convergence board when I pulled the main chassis, as it was a tight squeeze getting the chassis over the top of the board to pull it out. I'll give that a try this evening. Thanks!

That problem is not convergence board related.
In your original post, you stated a CTC38 chassis in the text. I think the set you have is a CTC36, which is simular to the CTC22 design.

[Kamakiri]

Right, good catch. I had it correct in the thread title.....

[ctc17]

Is CTC36 that 19inch tube deal with the low focus voltage crt?

Im blanking out right now on that. If so try moving the tubes around in the sockets. Or maybe you bumped the service switch.

[Kamakiri]

It uses a 19HNP22 picture tube, so I'm not sure if that qualifies as a low focus model

Tapped all the tubes, nothing. BUT, I did figure out that the retrace lines have something to do with the vertical sync section. When brought just out of lock, the lines get somewhat brighter, and pulled along with the sync when it was adjusted to freewheel very slowly. I cleaned the pot for the vertical hold, and for a brief while, the issue disappeared.

I may be wrong, but it seemed like it came back when the DeOxit dried up, which would lead me to believe that the cleaner in its wet form added some resistance to the circuit at that point? Normally I'd say no, it's just dirty.....but this wasn't happening before the ceramic cap blew.

For the moment, I tweaked the AGC, contrast, and brightness, so that it's barely visible. I mean after all, I need a television to watch, right?

[dieseljeep]

[QUOTE=ctc17;3059430]Is CTC36 that 19inch tube deal with the low focus voltage crt?

Those sets had a great picture on them when they were newer.
After they got a few years old, the focus seemed to be rather poor. Even if the CRT tested good and all three guns equal, the clairity was lacking. I have a CTC51K and a CTC53, same thing. I got used to seeing clear scan lines on a CRT set, but those sets are a disappointment.

[Kamakiri]

I have to say, the focus is pretty darn good on the set. These pics were shot before the "incident", but the picture is pretty much the same now, save a hint of retrace.....

I actually have two of these sets. The other has the "use it one day, it's working, turn it on later, and now the set has no sound or picture but has a full raster" issue that I seem to run into with late 60s RCA color sets. That'll be the next one I tear into.

[andy]

...

[DaveWM]

If it was better before a bad cap, and now you replaced a cap and it is not a good as it was, it would be logical to look and see if any resistors around that cap may have taken a large surge, and perhaps are now way out of spec. I see a diode in the vert blanking circuit, while I doubt its the problem would not hurt to check.

[Kamakiri]

Decided to put a couple more hours on the set tonight, and the result was the same.....light retrace. The picture started out jittery, but stabilized after about 10 minutes of play.

In the automotive field, there's some points in time where you have to allow the component to fail, to identify the root cause. Since my diagnostic skills leave something to be desired (I can spot the easy stuff), I decided to give that a try. Didn't woik .

Since there's only about a half dozen resistors on that board IIRC, I'm just going to go ahead and replace them all. I figure if you're going to take the time to desolder one end to take the resistor out of the circuit, you might as well just do the other end too and replace it......

[Kamakiri]

Meanwhile, I decided to play around with the set's twin brother that I have. It's a newer model, ES415W, which shows to be a CTC-53 chassis, with the 18VDBP22 picture tube. I saw a date inside of 1973 on one of the components, meaning this set must have been one of the last tube sets RCA made. Weird thing is that it's not a Mural set.

Physically, VERY close in appearance to the other set. Makes a nice picture, too....after cleaning dirty pots and just letting it run. Now, I just have to figure out how to adjust the horizontal centering......

My only complaint about these sets is that they take FOREVER to warm up and produce a picture. The sound comes on after about 10 seconds, then it takes so long to see anything on the screen, you'd swear you lost HV

[bgadow]

I'd forgotten about that trait-I have a pile of CTC-53's but only one inside and cleaned up. It holds my record, by a quite a bit, for longest warmup. I think I timed it at over 60 seconds to get a raster. I do find the picture they make to a have a pleasant quality. Biggest problem with my "good one" is something heat sensitive in the vert circuit that causes a lot of drift until it's good and warmed up. I've replaced the tubes and caps, not sure if I started replacing resistors or not. That set hasn't been turned on in probably 3 years

[DaveWM]

Dont forget to check that diode. I dont know what make it is but to be safe you should heat sink it before removal (you maybe able to check in circuit, did not look too close to know for sure).