RCA CTC-12 estate sale find

[Adam]

I picked up an RCA CTC-12 console at an estate sale this morning. Its one of those big entertainment centers, and I couldn't fit it in my trunk so paid half the price and am having the guy hold it for me until the weekend when I can come up with some way of transporting it.
It has some vert size issues. The UHF dial is jammed. And the back right leg is broken off.
Also only the green gun works. I am a bit worried the CRT is bad, but I would think if that were so either it would not work at all, or the red and blue would be dim but not nonexistant as it is here. If it is bad I do have a spare 21FJP22, but it has cataracts, and the green gun on that one reads completely dead, while red and blue are strong, but the socket is loose, and I bet it just has a wire to one of the pins broken. Actually, I don't even know if this takes the 21FJP22, when I get home I'll have to see if I have the schematics to this.

[bgadow]

Are all 3 filaments lit? If not you could tap lightly on the neck & hopefully that will put them back straight. Could just be misadjusted or some loose wires.

[jpdylon]

If its not the CRT, an all green condition can be caused by the color section, Bad B-Y R-Y vid outs, or bad screen network. I had a zenith that had only blue. CRT was good, but the screen pots were badly burned. The R-Y vid out tube was shorted. To get the three primary colors they take the R-Y and B-Y signals, and invert them to get the green. If one tube is bad you may ony get one color. I replaced that tube and the burned pots and everything was fine.

However since its green only i would lean towards screen controls or CRT.....

[Adam]

Thanks for the thoughts on the green only problem. I haven't really worked much on color TVs, as I really prefer tube sets so I just don't get as many as I do B&Ws. The first thing I'm going to do when I get this home is to put the CRT tester on it and see if its bad or not, I didn't even take the back off the set when I was at the sale. But it is still in the garage at the house of estate sale, I seriously think I'm going to have to rent a truck to get this thing home, I really don't want to as it is only about 2 miles from there to my apartment. But that is really too far to carry a set this big and there's no way I can get this thing to sit in my trunk, even if I take the lid off. I wish I had my 72 Impala running, I could have got it in there with the lid off.

[Adam]

I got this set home today. I actually had misidentifyed it, it is a CTC-15 not a 12. Anyway, I am relieved to find out that the CRT is good, all three guns, the red is a bit weaker than the other two, but still good.

[jpdylon]

First of all, try doing a greyscale setup on it. Turn all three guns completely down, flip the service switch and turn the red up until you just see a line, then blue until the line becomes magenta, then green to produce a dull white line. Flip the service switch back to normal and see if you havea B&W pic. If you had a white line but still have a green only pic, check the Y amp tubes. If you can't get a white line and the CRT is ok, check the Screen voltages on the CRT for the read and blue guns. It probably won't hurt to clean the tube sockets including the CRT socket either...

[Adam]

I cleaned the CRT socket already and checked for loose wires, I even tried lightly tapping the CRT neck. I just tried the service mode, no lines, no picture at all. I don't know if the switch is bad, or this is caused by the set's other problems. But basically I got not enough vert. size, combined with really weak horiz. sync., but once I did get the horiz. to sync. I saw the worst case of that wavy picture (usually caused by those stinking leaky filter caps) I have ever seen. The part of the screen which was 'pushed over' was about 3/4 of it and that whole section of the screen is green, but as it moved up, below it the screen would be b/w. I wouldn't be surprised if I changed those electrolytics, and found myself with an ordinary b/w picture, and just had a weak vert. out tube, maybe also a weak horiz. osc., and a few of those others weak in the color section as well. I'm going to go the the library and copy the schematic either tomarrow or next week (How can I have 900 folders of sams and never have the one I need).
An interesting note, I took the back off my 63 Philco color for comparison and found that the chassis was almost identical.

[bgadow]

There is a resistor between the height & vert lin controls which tends to go open, preventing you from getting full height. While you have the chassis out for the electrolytics (most important) take a look at it.

[Steve D.]

The Philco, except for the tuner, is identical to the CTC-15 chassis. The Philco SAMS is set 698 folder 4 if that helps.

-Steve D.

[Adam]

I'm still immersed in my B&W Hoffman now, but I pulled the tubes on this to go test them last week. I have a B&K 500 and a TV 11, but these are both too old to test all these tubes in these color sets, so when I was driving up north I took them all with me to a store up in Berkeley that still has a B&K 707 in use. I also went and copied the sams from the public library up there.

What I noticed about this TV when I was removing the tubes, that is odd, is that the UHF tuner is not the same one listed on either the tube diagram glued to the HV cage or in the sams. The one on the tube diagram is part number KRK 112, which uses a 6DV4 (one of those nuvistors) as an RF amp. The sams shows both that tuner, and for earlier models: KRK 66, which uses the 6AF4. The tuner in there is part number KRK 120C. It uses two tubes: the 6CB6 and the 6GK5, both of which, according to my recieving tube manual, are usually used as VHF (not UHF) RF amp tubes. I know those are the tubes that it is supposed to use, as it says so on the tuner itself. I took it apart and it does appear to be a tuner of some sort. Also it is made by RCA, and does fit perfectly in there, however, by the way the wires are connected to it, I can tell it is not original and was a later addition to this set. Maybe this just a later model tuner that was put in there later, by someone who wanted to get UHF, but then it seems odd that RCA would have went from the nuvistor unit to a two-tube unit. I would think that they would have went to a real transistor unit after that, most of the UHF tuners I've seen use a transistor for an RF amp, even in the mid-late 60s. Actually the only kinds I've ever seen are either the 6AF4 units, or the transistorised ones. And I've never seen a tuner with two RF amp tubes before, VHF or UHF.

[Adam]

I stayed up late last night and changed the electrolytics. The picture is full size, but it is still all green. There is a little blue, but no red at all. I checked the 21FJP22 again, and all 3 guns are good. I tried the setup mode, all I get is a 3/8 inch thick green line, even with the green turned all the way down and either red or blue or both all the way up. I tried to put a color bar generator on it just to see what would happen, it was all green, but what was interesting was when I turned it to show the crossed lines, it would show me the white lines (becuase of the little blue it has), but the background which should have been black was all green. And this is with the green screen and drive controls set all the way down. The brightness control, tint control and color control have almost no effect on the picture at all.

[Sandy G]

Sounds like Haints to me...

[frenchy]

Maybe a place to start would be measuring the voltages on the picture tube socket to be sure what's going to the 3 guns? But then I ain't no expert, better listen to them in here, not me... Frenchy

[Adam]

Adjusting the screen controls, the voltage there varies between 400 and 1000 volts on all 3 guns. Seems ok. An unhappy development, I tested the crt again, 3 months ago the green and blue guns read 3/4 of the way up the meter and the red 1/2, now the green and blue are the same, but the red only 1/4.


I'm still worried about my red gun, but at least I found what seems to be the problem, the grids are all off, green = 400v, blue =100v, red = 50v. They're supposed to be 160v.

Plate voltage is 300v on all guns (it says it should be 345v), I wouldn't think this is a serious problem.

[smoker76]

Originally Posted by bgadow

Are all 3 filaments lit? If not you could tap lightly on the neck & hopefully that will put them back straight. Could just be misadjusted or some loose wires.

I got a similar set with the 21FJP22 and the green gun filaments don't come on. I guess that's why the neck lights up too bright upon power-up but immediately go to normal glow. I am waiting on a B/K CRT tester to arrive.
I don't know how the filaments are arranged in there but from what was written I wonder if just sitting for years allows one filament to lay across another to short? If so, should I put the CRT upside down and give power before I try to use the "remove shorts" feature if the tester even shows it as a short.
Any advice? It is expected to be a good tube if I get the green filaments on because the set has been sitting since unused '73.