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 Post subject: Re: Alternatives for tubes on a Magnavox color roundie?
PostPosted: Mar Wed 12, 2014 2:16 pm 
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Joined: Nov Wed 23, 2011 4:40 pm
Posts: 328
Location: Somewhere on Planet Earth
About finding another record changer, it is possible but really I am more into keeping the original stuff. Also, this Magnavox record changer is so gentle when it comes to treat the records.... And last but not least, the "record size scanning system" that these people designed keeps me amazed so it is part of the fun also.

The speed of the turntable will be determined by speed of the motor and the ratio between the diameters of the rubber wheel that links the motor & the turning plate and the diameter of the different sections on the shaft of the motor (sorry for my lack of specific vocabulary). So, there are three things I can change to increase the speed.

If I reduce the diameter of the rubber wheel the speed will increase but I will run the risk of letting the plate and the motor unlinked... Increasing the diameter of the motor's shaft is what I did (only for the 33 1/3rpm section).

Last option would be to find a motor with the same diameters in the shaft but for 50Hz. Because of standards, 110V 50Hz is not an option, so I should go for a 220V motor and made all the modifications needed to keep the auto power off mechanism active. Anyway finding a motor with the exact diameters on it will be very difficult but I can try.

Did you watch this video that I posted right after I implemented the supplement on the motor shaft? The lyrics make the turntable speak :)

http://www.youtube.com/watch?v=ILalllJD ... e=youtu.be


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 Post subject: Re: Alternatives for tubes on a Magnavox color roundie?
PostPosted: Mar Wed 12, 2014 2:27 pm 
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Location: Warner Robins, GA
I think that is a collaro changer and if so there may be a 50 Hz version that looks just like the one you have. If that can't be found you may be able to find a motor for 50 Hz operation. If the spindle can be removed from the motor shaft and you find a 240 V 50 Hz motor just swap spindles.

If the spindle cannot be removed and both motors look the same you may be able to swap the whole top bearing assembly with the rotor and shaft.

I always thought changing the diameter of the rubber drive wheel would affect speed, but some have said it doesn't affect speed at all.

Don't know if it will work or if it is affordable, but you could try a variable frequency drive used for motors and set it to 60 Hz. It would connect before the step down transformer.


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 Post subject: Re: Alternatives for tubes on a Magnavox color roundie?
PostPosted: Mar Wed 12, 2014 4:35 pm 
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Location: Somewhere on Planet Earth
Interesting idea, maybe I can come up with my own frequency converter out of some circuit around on the internet.

Getting the same record changer here is not an option, they were never imported to here. I will dig into the motor itself and see what I can do with the spindle if I come across with a compatible 50Hz motor, that may also work.

Thanks a lot for the tips!


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 Post subject: Re: Alternatives for tubes on a Magnavox color roundie?
PostPosted: Mar Wed 12, 2014 5:09 pm 
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You're welcome.

I would suggest truying to find one on the internet, but that won't work as you mentioned about no imports except certain things.

Maybe find one and have it shipped to a friends or relative's house in another country and get it next time you go see them.


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 Post subject: Re: Alternatives for tubes on a Magnavox color roundie?
PostPosted: Mar Wed 12, 2014 6:57 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 596
Location: Asheville, NC USA
I am so sorry that you are having such trouble getting things into your country.

With luck, you can find the 50 cycle motor for your turntable.

Can you post a picture of your motor?

The picture on your set looks great, to me. I'm so glad to see another Maggie returned to the world of the working units... Especially an entertainment center. I've seen so many of them scrapped.


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 Post subject: Re: Alternatives for tubes on a Magnavox color roundie?
PostPosted: Mar Fri 14, 2014 12:56 pm 
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Location: Somewhere on Planet Earth
I have a problem with the internet at home which is supposed to last for a week or even more...

I will take the back cover out and take a pic of the motor.

I noticed that the colors were not that bright (though nice, and the CRT had a lot of range of screen and brightness), and reading an old set up manual online I found out how to set the bias control correctly. I had set them full clock counter-wise and from there I set up the screen controls. Wrong! The book recommended to set up the bias controls 30% less than full clock-wise and start from there adjusting the screen. And it really made the difference! It looks like if it had much more contrast.

I adjusted the convergence as good as I could, and now in its definitive resting place it seems like something changed (I moved the console around the room and I placed that loudspeaker close to it). I don't know if this has something to do with it but anyway it is watchable from a distance :) What is annoying is that shaking up and down effect on the left side. I wonder if that could be caused by a cap.

Here is a new example of how it looks with the new bias set-up (the H-center is a bit off but I just corrected it after taking the pic with the H-hold control, and the yoke is a bit tilted, I will fix that later):

Image


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 Post subject: Re: Alternatives for tubes on a Magnavox color roundie?
PostPosted: Mar Fri 14, 2014 2:10 pm 
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Location: Fernandina Beach, FL
Well, that certainly looks good. I wonder if that set looked that good from the factory?

Congratulations.

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 Post subject: Re: Alternatives for tubes on a Magnavox color roundie?
PostPosted: Mar Fri 14, 2014 3:06 pm 
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Location: Woodinville, WA USA
Normende, I have to tip my hat to you. That picture looks great -- as good or better than any color roundie that I have seen. The colors look very natural, and I know from experience how difficult it can be to get the convergence correct from edge to edge, not only in the middle.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html


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 Post subject: Re: Alternatives for tubes on a Magnavox color roundie?
PostPosted: Mar Fri 14, 2014 5:54 pm 
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Joined: Nov Wed 23, 2011 4:40 pm
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Don and Phil, thanks a lot for your comments. This makes me feel even more happy :)

Without all of the people that helped me through this process this would have never been possible!

The colors on this set look so solid and so warm, definitely something special... From now own there is one more item on my list of "must be":

- Vinyls over CDs
- Tubes over transistors in audio
- Tubes over transistors in video :)


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 Post subject: Re: Alternatives for tubes on a Magnavox color roundie?
PostPosted: Mar Sat 15, 2014 12:49 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 596
Location: Asheville, NC USA
I think your set looks fantastic.

I know that ELO logo, and it looks 'RIGHT.'

When you take a picture of the motor, just a shot from the back of the set looking up at the motor from below will be enough for me to tell which motor you have.

Bruce McGee
Asheville, North Carolina


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 Post subject: Re: Alternatives for tubes on a Magnavox color roundie?
PostPosted: Aug Sun 17, 2014 8:33 pm 
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Joined: Nov Wed 23, 2011 4:40 pm
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Hi all,

I'm back with a question after quite a while.

After some time the CRT of the set got magnetized, and so my neverending recursive exhausting purity and convergence adjustment work just vanished :(

The thing is, the thermistor and the varistor of the internal degaussing coil have a failure. I knew that, but I didn't think the CRT would get magnetized so soon without moving the set around the room.

I saw that there is a website from a company in the US (Talon Electronics) that sells NOS thermistor/varistor pairs for RCA sets. They look pretty much the same ones my set has, but there are several options in the catalog (GBTV, GBTV-1,2,5,7.....). This is the link where you can find pictures of each of them in their original baf where there is even a small label with a description in some of them:

http://www.talonix.com/shop/category.aspx?catid=69#.U_D_YsVdWSp

Do you know which model number on the list would be suitable for RCA CTC-15 / CTC-16? The schematics I have do not mention part numbers on these elements.

I can't buy them online because of incomprenhensible regulations (I talked about that before...), but I can be aware of someone traveling to the US sometime in the future. Maybe that could be the only way for me to get them.

Thanks in advance as usual!

@Bruce: After having spent SO many nights without sleep working on the set I didn't open the set again. Whenever I had to do it, I would check the motor model and let you know. Thanks!

@All: I edited this msg a lot of times because I am not using a translator to write and English is not my first language :) so revision is a must (and "preview" instead of "submit" should be a must too but I am still struggling to be a bit less anxious hehe)


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 Post subject: Re: Alternatives for tubes on a Magnavox color roundie?
PostPosted: Aug Sun 17, 2014 10:01 pm 
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Most likely unless the speaker sitting near the TV is shielded it has caused your problem.

Now once the degaussing circuit is fixed then that shouldn't be a problem.


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 Post subject: Re: Alternatives for tubes on a Magnavox color roundie?
PostPosted: Aug Mon 18, 2014 4:37 pm 
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Yes, maybe.... An also, I had to add a 220V/110V transformer inside of the cabinet to use it in our network (220V, less current, less money invested on copper out there, but more dangerous of course).
I placed it as far as possible from the CRT, against one of the sides, but anyway that was not something the set was meant to have originally so it may have some influence too.
I hope I can make the convergence coil work again so things will get back to normal every time I turn on the set... For now I had to short the thermistor in order to get a decent +B on the power supply, and the varistor is death.


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 Post subject: Re: Alternatives for tubes on a Magnavox color roundie?
PostPosted: Aug Mon 18, 2014 7:02 pm 
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I doubt that transformer would cause the issue, although if the transformer is powered all the time I don't know.

One way to test if it is the speaker is move it in front of the CRT then move it away and see if it affects it at all.


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 Post subject: Re: Alternatives for tubes on a Magnavox color roundie?
PostPosted: Aug Tue 19, 2014 4:33 am 
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normende wrote:
I can't buy them online because of incomprenhensible regulations (I talked about that before...), but I can be aware of someone traveling to the US sometime in the future. Maybe that could be the only way for me to get them.
Is it possible for someone in the US to buy the part and then mail it to you? If so, I'd be willing to help. You can send me a PM to make arrangements.

Regards,

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html


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 Post subject: Re: Alternatives for tubes on a Magnavox color roundie?
PostPosted: Aug Tue 19, 2014 5:03 am 
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You can degauss it manually if you can find something that can produce an AC field. One time I used a soldering gun who's transformer had a large external field. I had to work quickly so as not to burn up the tip. I turned it on some distance away from the CRT, brought the back end of the gun up to the screen and moved it around in a circular motion and then moved it away from the CRT before turning it off. You have to move it away somewhat slowly, but slowly can be 1 to 2 seconds.

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 Post subject: Re: Alternatives for tubes on a Magnavox color roundie?
PostPosted: Jan Wed 08, 2020 5:59 pm 
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Joined: Nov Wed 23, 2011 4:40 pm
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Location: Somewhere on Planet Earth
Hi all,

Im resurrecting an old post from long ago in which I received unvaluable help from a lot of people in this forum. Not only with information and tips but also with free parts sent overseas even for free. Fortunately I was able to resurrect this tv which is unique here as color tv broadcast started here i 1979 so no tube color tvs were being sold.

There is something I never solved in this tv and it has to do with the degaussing components that are bad. Back then Phil kindly offer to help with this but I had to leave the project for a while.

Do you know if these components have to be identical to the original ones or can I use whatever I can find here? I guess differences in values should not be a big deal right?

Thanks in advance!


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 Post subject: Re: Alternatives for tubes on a Magnavox color roundie?
PostPosted: Jan Thu 09, 2020 8:24 am 
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Location: Belrose, NSW, Australia
You should be able to use similar local parts designed for 220v. The common Philips dual PTC and resistor should work just fine.

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 Post subject: Re: Alternatives for tubes on a Magnavox color roundie?
PostPosted: Jan Thu 09, 2020 1:36 pm 
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Joined: Nov Wed 23, 2011 4:40 pm
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Location: Somewhere on Planet Earth
Thanks for the info. I will start looking what i can find here then.

Anyone has the specs of these two components? I could just find on the schematics that the resistor is 120ohms cold.


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 Post subject: Re: Alternatives for tubes on a Magnavox color roundie?
PostPosted: Jan Thu 09, 2020 2:14 pm 
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Joined: Nov Sun 11, 2018 12:32 am
Posts: 40
Normende, I'm so glad you started this thread and that you found that TV, though I'm super bummed that the photos have disappeared from the thread.

Through reading through this old thread I've come up with a solution for a problem I'm facing myself! I'm in Spain, and have a 1963 Magnavox Imperial console stereo which probably arrived here much the same way your combo arrived to Argentina. I've done a full restoration of the electronics, but the record changer has always been an unsolveable problem. I don't want to put a 50Hz Collaro because it wouldn't be original (they don't look the same). BUT adding some heat shrink to the motor shaft is a brilliant idea and I'm going to try it as soon as I can. So, thanks for the idea!

Also FYI should you ever need service information for the stereo portion of your combo, Magnavox equipment model numbers are kind of weird due to the millions of combinations of cabinet style, finish, tuner chassis, amp chassis, multiplex adapter, speaker system, etc., so you generally go by chassis number for each component. My amp chassis is a 9300-10, and was used in dozens of different models, so there is a Sams just for that chassis. You can find downloadable versions of all Magnavox schematics, service manuals, sales brochures, and instruction manuals in the Downloads section of vintagehifi.net.


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