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 Post subject: Ctc 11 vertical rolling until warm up.
PostPosted: Mar Thu 12, 2020 12:10 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Waukegan, IL
Ctc 11. Vertical will roll for a few minutes until set warms. Then it locks. Which component is drifted? Has new vert tube. Replace both the 80 and the 50 mfd capacitors in the vertical circuit. The 50 mfd is on the board, and the 80 mfd is a filter cap.

There is a 2000kv capacitor to ground in the feedback loop. Im suspecting that. What do you guys think?

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 Post subject: Re: Ctc 11 vertical rolling until warm up.
PostPosted: Mar Thu 12, 2020 12:44 am 
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Location: Belrose, NSW, Australia
"A few minutes" sounds more like a tube (vertical oscillator) fault. Try a couple more tubes if you can.

In Oz this fault was very common with TVs using 6GV8s in the vertical. Even new tubes could exhibit this fault.

One set maker (Kriesler) collected all the 6GV8s they'd failed in TV production and used them for the audio in what was probably the last tube mantle radio to be made anywhere in the world, the 11-99. Not long after TV production went solid state, the 11-99 was discontinued.
They made LOTS of these, they are still commonly found and I've never seen one that didn't still work!

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 Post subject: Re: Ctc 11 vertical rolling until warm up.
PostPosted: Mar Thu 12, 2020 1:19 am 
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Location: Waukegan, IL
And it was a new tube without a whole lot of use since. Something else is out of whack as the hold control is not centered. Its almost to the extreme CCW rotation to get lock.

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 Post subject: Re: Ctc 11 vertical rolling until warm up.
PostPosted: Mar Thu 12, 2020 1:52 am 
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Location: Ann Arbor, MI
The parts that heat up the quickest are the tubes. The next quickest are any resistors that have enough current through them to dissipate noticeable heat. The capacitors generally take 10 to 20 minutes to heat up. But failing electrolytic caps can heat up quicker than that.
New tubes can be bad.
The parts in the vertical circuit that determine the frequency it operates at are various capacitors and resistors around the oscillator. A capacitor and resistor pair determines the time constant that determines the frequency. Some other capacitor and resistor pairs can pull the frequency around somewhat. I don't have a schematic for your set so I can't mention any specific parts.

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 Post subject: Re: Ctc 11 vertical rolling until warm up.
PostPosted: Mar Thu 12, 2020 1:05 pm 
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trainman wrote:
Ctc 11. Vertical will roll for a few minutes until set warms. Then it locks. Which component is drifted? Has new vert tube. Replace both the 80 and the 50 mfd capacitors in the vertical circuit. The 50 mfd is on the board, and the 80 mfd is a filter cap.

There is a 2000kv capacitor to ground in the feedback loop. Im suspecting that. What do you guys think?


You already replaced the tube, so use component cooler to isolate the problem. It should start rolling again when the drifting component is cooled.

Ed

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 Post subject: Re: Ctc 11 vertical rolling until warm up.
PostPosted: Mar Thu 12, 2020 6:30 pm 
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Joined: Jun Mon 24, 2013 3:00 pm
Posts: 1493
Location: Champaign IL 61822
It may not be a drifting cap or resistor, rather, a defective resistor
that jumps in value when heated under load. My CT-100
had this problem. After futile attempts to find the bad resistor,
including cooler spray, I replaced ALL of them and it was fixed. This would also fix,
of course, another possible cause: a solder joint that is not solid.


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 Post subject: Re: Ctc 11 vertical rolling until warm up.
PostPosted: Mar Fri 13, 2020 5:50 am 
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Location: Belrose, NSW, Australia
Well, with the TV model I was talking about, you could sometimes try 3 new tubes before you got a good one!
Another manufacturer added a transistor to the oscillator to get a clean end-of-scan switch and so design the variable tube characteristics out.
With tube circuits, unfortunately it isn't just the passive components that set the frequency. Tubes are not perfect, it's as simple as that, and their characteristics do shift around.

Attachment:
CTC11_Vert.png
CTC11_Vert.png [ 55.16 KiB | Viewed 1036 times ]


So it still sounds like the tube to me. The timing is too short to be anything else. Even a paper cap (I assume you have already replaced them all) would take half an hour to react and cause other symptoms as well. Assuming all poly caps, it's VERY unlikely to be one of them. And defective resistors tend to jump around, not drift slowly.

The only TV I ever saw in Oz to use the 6EM7 was an Admiral, about the same period. Yes, they suffered from rolling from cold and replacing the 6EM7 fixed it.

Edit: I checked and no not Admiral, AWA D1, D3 or T31. Early '60s. Used a blocking oscillator circuit. I watched the moon landing on one of these!

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Last edited by irob2345 on Mar Wed 18, 2020 10:31 am, edited 1 time in total.

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 Post subject: Re: Ctc 11 vertical rolling until warm up.
PostPosted: Mar Fri 13, 2020 4:32 pm 
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Location: Pewaukee, WI
One trick for identifying bad tubes is to wait till fully warm then power off for 8-10sec then switch back on...any stage that appears to not be functioning 100% once the screen is lit probably has a tube that is getting worn out.


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 Post subject: Re: Ctc 11 vertical rolling until warm up.
PostPosted: Mar Sat 14, 2020 1:08 am 
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Location: Belrose, NSW, Australia
Woah! NOS 6EM7s have got EXPENSIVE!

Seems the audiophools have discovered them.... :(

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 Post subject: Re: Ctc 11 vertical rolling until warm up.
PostPosted: Mar Sat 14, 2020 11:15 am 
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All of the components in the feedback pathway from pin 2 to pin 4 of the tube would be suspects (assuming the tube is ruled out) so that is 8 components, any change in these would alter the operating frequency. The other feedback arm (that completes the multi-vibrator) from pin 5 to pin 1 could also have some effects on the frequency, but more the scan amplitude & linearity. And obviously the heater & HT voltages should be checked for stability before assuming the problem lies inside this circuitry, rather than outside it.


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 Post subject: Re: Ctc 11 vertical rolling until warm up.
PostPosted: Mar Sat 14, 2020 11:40 am 
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Joined: Jan Thu 16, 2020 12:29 am
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irob2345 wrote:
Woah! NOS 6EM7s have got EXPENSIVE!

Seems the audiophools have discovered them.... :(


That is very unfortunate.

They have adopted a large number of TV tubes now (previously called sweep tubes).

I tried to explain to the audiophile fraternity, in detail, that these tubes have inferior sonics, high microphony, little punch, an unpleasant tone color, no warmth, probably not even black plates a lot of the time and generally have very uncool vibes. But it is what they do to the mid-range tones that is so disheartening, I can hardly bare to talk about it. Also, after listening to sweep tubes, for an hour or more it is so fatiguing, it is a real bummer and gives the listener a really bad trip man. These sweep tubes have a kind of unnatural mechanistic "machinery sound" (hardly surprising since they were designed as deflection oscillators & deflection amplifiers) spoiling the entire audio experience, to say nothing of the Mojo and making the music very robotic & cold, it is as though they have no emotion at all, But my dire warnings fell on deaf ears, the audiophiles "wouldn't listen" and the prices of TV sweep tubes went over the moon.


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 Post subject: Re: Ctc 11 vertical rolling until warm up.
PostPosted: Mar Sat 14, 2020 7:37 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 750
Location: dayton oh usa
sweep tubes have gotten pricey because cb'ers use them in cheap n nasty amplifiers up to 12 at a time.
and they have a very short life in that service.
ACORNVALVE wrote:
irob2345 wrote:
Woah! NOS 6EM7s have got EXPENSIVE!

Seems the audiophools have discovered them.... :(


That is very unfortunate.

They have adopted a large number of TV tubes now (previously called sweep tubes).

I tried to explain to the audiophile fraternity, in detail, that these tubes have inferior sonics, high microphony, little punch, an unpleasant tone color, no warmth, probably not even black plates a lot of the time and generally have very uncool vibes. But it is what they do to the mid-range tones that is so disheartening, I can hardly bare to talk about it. Also, after listening to sweep tubes, for an hour or more it is so fatiguing, it is a real bummer and gives the listener a really bad trip man. These sweep tubes have a kind of unnatural mechanistic "machinery sound" (hardly surprising since they were designed as deflection oscillators & deflection amplifiers) spoiling the entire audio experience, to say nothing of the Mojo and making the music very robotic & cold, it is as though they have no emotion at all, But my dire warnings fell on deaf ears, the audiophiles "wouldn't listen" and the prices of TV sweep tubes went over the moon.


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 Post subject: Re: Ctc 11 vertical rolling until warm up.
PostPosted: Mar Sun 15, 2020 3:05 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 653
Location: Stafford, Texas USA
I remembered that CTC 11s chassis had notorious problems with solder joints that connect the boards to chassis ground lugs and the tube sockets pins.
Resolder all of the ground joints, tube sockets pins and clean all the old flux off.

After 50 years solder joints have not got any better.

Never had any problems with 6EM7's.

Jimmie


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 Post subject: Re: Ctc 11 vertical rolling until warm up.
PostPosted: Mar Sun 15, 2020 11:15 am 
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Joined: May Sun 07, 2017 11:35 am
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Location: Belrose, NSW, Australia
Getting hard to buy 6CM5s (Hor OP tube) for TVs. for that reason.

Crazy! You couldn't imagine a worse choice for an audio amplifier, that is, of course, unless you wanted to achieve 25% THD!
This tube is designed to function as a SWITCH! Plate dissipation does not support any useful amount of power.

Sure, they were once used in PA amplifiers (by none other than Philips would you believe), but as others have suggested they don't last long in the role.

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 Post subject: Re: Ctc 11 vertical rolling until warm up.
PostPosted: Mar Mon 16, 2020 3:03 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 2045
Location: Waukegan, IL
well, it was the tube. i thought i had changed the tube since i bought a new one. no, the old tube, maybe orignal, was still in there.

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 Post subject: Re: Ctc 11 vertical rolling until warm up.
PostPosted: Mar Mon 16, 2020 5:27 am 
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I have a CTC11. It had the same problem. First thing I did was replace the capacitors. This fixed the problem.

The clue is if the oscillator is running too fast or too slow. If too fast, it is capacitor leakage. If too slow, it is generally a carbon resistor which has drifted upwards.


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 Post subject: Re: Ctc 11 vertical rolling until warm up.
PostPosted: Mar Mon 16, 2020 11:31 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 2045
Location: Waukegan, IL
Ctc 11 has polyester caps. I only found one coupling cap passing excessive DC voltage. Only ones I changed were the elmenco ceramic tube ones. Those are oil and paper dielectric. I pulled the 600v elmenco across the horizontal freq. Coil. Leaks. The 1200v elmenco on the vertical board doesnt leak at 600v, but i cant test it higher. I left it in, for now.

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 Post subject: Re: Ctc 11 vertical rolling until warm up.
PostPosted: Mar Wed 18, 2020 2:15 am 
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Posts: 925
Location: Belrose, NSW, Australia
Thanks for letting us know Tony. Always pays to check the obvious first.

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