Rca Ctc-15

[Charlie]

Another project I decided to start is a CTC-15. I have two of them in the garage... one in a metal cabinet and one in a Beauchamp wood cabinet. Currently, neither one has a CRT. The plan is to put the better of the two chassis into the Beauchamp cabinet, which will be stripped and refinished.

Since i didn't get very far with the Philco today, I decided to bring up the 15 on the variac. (I have a feeling that I'll be jogging back and forth between these two sets) I was glad when it started picking up audio from our local channels by the time I got it to 80 volts... at least I know the first few stages are operating. After finally getting it up to full power, B+ voltages looked good and audio was good and clear. I found one lytic that was slightly warm, but not too bad to worry with at this time.

Before powering it up, I found a couple of wires that had burned in two from being next to a 10 watt resistor. Also, looks like the HV anode lead needs replacing due to a crack in the insulation.

[Charlie]

Tonight I decided to hook up a picture toob to this CTC15 chassis. The only CRT I felt safe plugging in was in a wooden CTC11 set... this particular set's toob has severe cataracts and is weak on one of the guns, but works. I yanked the 11 chassis out, and half-ass squeezed the 15 chassis partially into the cabinet. It's not pretty, but will do for testing purposes.

After plugging the horz output tube back in, I had the pleasant sound of soft HV crackle, and then light on the screen with stations tuning in good... so good that I actually got a few Houston stations 90 miles away in addition to our own by only using an 18 inch jumper wire as an antenna.

The picture looked a bit out of focus, but that's likely from the cataracts... they're pretty bad all the way to the center of the screen. Looks like the color circuits are working as well. I let it run for 15 minutes and then decided it was way past bedtime.

Tomorrow I'll run it some more and do a few checks here and there. The chassis needs all of the pots cleaned, but was out of cleaner spray so I'll get some in the morning. Still got a few caps to upgrade with orange drops.

Since things are looking positive for this chassis so far, I'll get started on stripping the cabinet that it's going in. Feels good to know I'm making progress!

I was going to take some pictures of tonight's progress, but realized I left my camera at the camp today. Oh well. Here's a photo of the 11 that the 15 is squeezed into. As you can see, it needs some serious eye surgery!

[Charlie]

This morning I ran the 15 some more. After running it for 30 minutes, the only problem I found was the flyback running hot. Man I hate having to deal with HV problems! When I yank the chassis back out, I'll check the caps under the hz-output tube.

Any other suggestions?

[Jeffhs]

Originally posted by Charlie
Tonight I decided to hook up a picture toob to this CTC15 chassis. The only CRT I felt safe plugging in was in a wooden CTC11 set... this particular set's toob has severe cataracts and is weak on one of the guns, but works. I yanked the 11 chassis out, and half-ass squeezed the 15 chassis partially into the cabinet. It's not pretty, but will do for testing purposes.

After plugging the horz output tube back in, I had the pleasant sound of soft HV crackle, and then light on the screen with stations tuning in good... so good that I actually got a few Houston stations 90 miles away in addition to our own by only using an 18 inch jumper wire as an antenna.

The picture looked a bit out of focus, but that's likely from the cataracts... they're pretty bad all the way to the center of the screen. Looks like the color circuits are working as well. I let it run for 15 minutes and then decided it was way past bedtime.

Tomorrow I'll run it some more and do a few checks here and there. The chassis needs all of the pots cleaned, but was out of cleaner spray so I'll get some in the morning. Still got a few caps to upgrade with orange drops.

Since things are looking positive for this chassis so far, I'll get started on stripping the cabinet that it's going in. Feels good to know I'm making progress!

I was going to take some pictures of tonight's progress, but realized I left my camera at the camp today. Oh well. Here's a photo of the 11 that the 15 is squeezed into. As you can see, it needs some serious eye surgery!

Charlie,

How can you tell just by looking at the front of the set the CRT is defective? (BTW, what are cataracts on a picture tube? I've seen them mentioned in threads here, but never really knew what kind of defects they actually are [never heard of them until now], even after 30-odd years of experimenting with old sets back in my hometown.) Looks to me like the screen is just very dirty (filthy, even), and a good cleaning should have it looking a lot better.

I couldn't believe it when I read in your post that you were getting not only your area's local Beaumont/Port Arthur, TX TV stations, but also Houston stations 90 miles distant, on your RCA CTC15, just using an 18-inch alligator clip lead. The signal propagation conditions that day must have been incredible or even phenomenal. I am an amateur radio operator and have gotten incredible distance reception on both my radios and TVs in the summer, but I had external antennas on my sets at the time. My best distance reception on TV was KTWO-TV, the then-NBC affiliate in Cheyenne, Wyoming, one summer about 15 years ago, when I still lived in suburban Cleveland, but I have also received one of your area's local stations (channel 4 in Port Arthur, Texas) during a temperature inversion about 25 years ago, give or take a couple years. The reason I was able to receive so many stations in the Southwest is that my TV antenna was aimed in that direction (the local TV stations in my area at the time, and where I live now as well, all transmit from a Cleveland suburb some 45 miles southwest of here). When the TV bands opened up to the Southwest, the floodgates opened up and I would get incredible reception from Wyoming, Texas, Oklahoma, Florida . . . literally, you name it. The pictures, as long as they lasted, were often good enough to watch, but much of the time I would get a hodgepodge of stations, almost impossible to decipher. When one signal would eventually fade out, another would appear underneath it, and so on.

I have cable where I live today (TV reception from Cleveland, at least on VHF channels, is fair to poor at best here without it or a satellite hookup, even with a fringe-area outdoor antenna with an amplifier; in fact I cannot get one channel, NBC channel 3, on an antenna--the irony, however, is that most of the Cleveland UHF stations come in clear as a bell even on rabbit ears), which has pretty much put the kibosh on distant TV reception for me (I cannot use outdoor antennas here as I live in an apartment building). However, a couple summers ago, there must have been a temperature inversion, as channel 4 (one of our local UHF stations is downconverted to that channel by the cable company) was a mess, with Venetian blind interference, co-channel, you name it. Couldn't make out what stations were wiping out the local station (UPN channel 43, downconverted to 4), though I think it may have been either WDIV NBC4 in Detroit or WCMH NBC4 in Columbus, Ohio (out here on the fringes of the Cleveland stations, one can never tell what might appear on vacant channels, or between the local stations on the FM radio dial for that matter, during an inversion or even during normal weather in the spring and summer). I called the cable company and was told the problem was due to weather conditions, as I had suspected all along.

BTW (2): I just took another look at your CTC15 in the CTC11's cabinet. Looks to me like the 15 fits rather well in there. Am I overlooking something? I ask this because it seems to me you've managed to fit the CTC15 completely into the other cabinet, not just partially (as you mentioned).

BTW (3): Once you refinish that cabinet you will have one fine piece of furniture. RCA offers only one console TV today, as does GS/Zenith; I suspect the cabinets are made by a cabinet maker in North Carolina (Thomasville comes to mind). However, most TVs today are table models; as I've mentioned elsewhere in this forum that most folks wanting consoles these days simply get an entertainment-center cabinet and fit the TV, VCR and possibly a bookshelf stereo in it. These cabinets are nice, but the large ones can take up an entire wall (a friend of mine has his TV, VCR and stereo in one of these monsters; I've seen it--yes, it takes up a good part of a wall in his family room). I put my own TV, VCR and cable box on a small utility cart just a tad smaller than a small console; it all fits nicely in a corner of my apartment (my stereo is immediately adjacent to my computer, with the speakers on the floor on either side of my desk; my avatar shows the TV installation.)

BTW (4): The armoire-styled console TV/stereo units made by RCA and Magnavox in the late '60s would have been great for people living in apartments as small as or even smaller than mine, as I've mentioned here before. I've often wondered why RCA doesn't offer this style of cabinet, with an up-to-date TV in it of course, today. (The company does have one console in its deluxe line of 27-inch TVs, but it is a standard floor model.) If I were a betting man (which I'm not), I'd be willing to bet the vertical console design, even without the stereo, would be an instant hit with apartment dwellers or folks with small living rooms wanting large-screen CRT-based TVs.

[Charlie]

21FJP22's get this condition because the safety glass is coming unglued from the face of the CRT. 21AXP's, CYP's, and FBP's do not use the glued on safety glass.

The tube itself can be very good electronically.

If you'll look towards the bottom of this page, this is wide discussion on cataracts. In fact, there is a photo of Rob removing the safety glass.

http://www.audiokarma.org/forums/sho...5&pagenumber=3

Yes, every now and then I can get some really good DX-ing on TV. I have seen nights in which the distant stations are almost as clear as the locals. Several years ago, I was able to pick up Corpus Christi 300 miles down the Texas coast... for an entire week! That was really somethin! In fact, at night it was causing problems for picking up the locals here. The channel 6 in Corpus was bleeding thru the channel 6 here at home. Several months back, I picked up what I believe was a station in Mexico. At first, I thought it was a Mexican station out of Houston... till I realized the call letters started with neither a K or W.

[Kamakiri]

Don't waste your time doing it with chemicals and such.....

http://www.audiokarma.org/forums/sho...?threadid=6740

[Charlie]

Jeff,

The photo here shows a 21FJP22 with severe cataracts. As you can see, the only place in which the glue is still intact is the clean area in the dead center.

If mold or mildew starts to get between the two pieces of glass, it turns black like this one did. Sometimes, it may be light cataracts, which is the greenish looking "halo" seen around the outer edge of the tube.

If you have a FJP with cataracts and good emisions, you can take on the task of removing the safety glass, and then you have a FBP.

This can happen with some of the early rectangular tubes as well, but in most cases it is only the green halo.

[Charlie]

Here is a photo of the 15 chassis squeezed into the 11 cabinet. It almost fits! I did this only for testing purposes since I dont have a 15 cabinet that has a tube installed in it.

The other photo you saw still had the original 11 in the cabinet.

[Charlie]

Went out to toy around with this CTC15 chassis some more. Last time I ran it, the flyback was running hot after 30 to 45 minutes of operation.

I checked the current off the 6JE6 HO tube. It was running about 220ma. The schematic says not to let it run over 210. I adjusted it down to 205ma, but the flyback is still getting hot enough to where the wax bubbles in the middle.

Everything else seems to be running just fine. Any suggestions?

[Chad Hauris]

Sometimes the 6BK4 circuit can load the HV down too much, causing the flyback to overheat...check the voltage drop across the 1000 ohm cathode resistor...should be between .8 and 1 volt (800-1000 microamps). If it is more, then check the HV adjustment, also use a probe on the HV if possible to see if it is low because of excessive 6BK4 current.

Resistors in the 6BK4 cathode/grid circuit can change value, causing excessive current draw.

[Charlie]

Chad,

Thank you for the pointers. I never really cared for dealing with HV problems, and luckily they're few and far between for me.

I've made the checks you mentioned, and so far have made a few adjustments here and there. The 1000 ohm resistor you mentioned is not included in my set. From the Sams diagram, it looks like it isn't used in all of the models.

Since making these current adjustments involves using two meters at the same time, I made a trip to Rat Shack and bought another. Before that, I was having to joggle my meter back and forth between the HO tube and regulator.

My first readings on the cathode lead of the regulator was roughly 1500uA... far more than it needed to be. It would fluctuate some, but in any case it was somewhat high. A local friend suggested changing the HV rectifier, and so I did. This brought the current down to to 950uA initially, but I notice that it fluctuates and slowly falls as the set continues to run. In fact, it slowly falls as far down as 300uA after operating nearly an hour. In the meantime, Sam mentions not letting it fall below 850. I did try changing the regulator tube, but doing so had no affect.

The 1.5 meg resistors in the regulator circuit check right on the money.

The HV was running at 24,000 volts, so I tuned that down to 23,000. It seems to be pretty steady.

I've got the HO tube current tuned down to 202mA, and it's pretty steady as well.

With all this being said, the flyback still gets hot, but not near as bad or quickly as before. Before these adjustments and changing the rectifier, it would get damn hot after 30 minutes of operation... enough for wax to bubble. Now, it takes at least an hour to get hot... but this time without wax spitting out of it. So, it has cooled down some, but not enough. BTW... I still have a good stable picture.

Could my flyback simply have a minor short? Or could there be something else causing my problem?

[Chad Hauris]

Charlie, compare the flyback temperature to some other tube sets with similar characteristics...the heat you feel now that you have fixed the problems may be normal.

[Charlie]

Originally posted by Chad Hauris
the heat you feel now that you have fixed the problems may be normal.

I had considered that some heat is probably normal, but this flyback eventually gets hot enough to where you cant touch it in some areas.

I do recall that the flyback in my Curtis Mathes (a CTC15 clone)gets "warm" after a good while. I had never bothered with checking the current in that one because I didn't feel it was warm enough to be evidence of a problem.

Perhaps I am worrying over this too much, but I hear so many of the guys mentioning their flybacks being cool as a cuke.

I guess i'll just run it some more... maybe for a few hours straight... and just keep monitoring it.

[andy]

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[Charlie]

Well, it turns out that the flyback is still getting hot enough to bubble... it just takes longer. Started bubbling wax after 75 minutes of operating.

The cathode current on the regulator tube slowly dropped all the way down to 100 microamps! That can't be normal.