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 Post subject: Turret tuner; What am I missing?
PostPosted: Nov Wed 27, 2019 8:47 pm 
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Location: Redding, CA
I am nearing completion of restoring a 1949 Admiral television chassis and have learned that there is no response from the fine tune control. The fine tuning control operates a phenolic cam but whatever the cam was intended to operate is missing. What is missing and where can I find a replacement?

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Norman

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 Post subject: Re: Turret tuner; What am I missing?
PostPosted: Nov Wed 27, 2019 8:55 pm 
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Joined: May Fri 29, 2009 4:35 am
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Location: Chicago, IL USA
There's actually nothing missing. That "cam" is the dielectric for a small variable capacitor. The metal pieces are the two sides of the cap.


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 Post subject: Re: Turret tuner; What am I missing?
PostPosted: Nov Wed 27, 2019 9:23 pm 
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Location: Redding, CA
Thanks for the clarification. Should the cam be flush with the button? There is a blob of solder preventing the cam from contacting the face of the button.

Norman

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 Post subject: Re: Turret tuner; What am I missing?
PostPosted: Nov Wed 27, 2019 9:56 pm 
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No, I think that's all factory original. The solder blob is for wire connecting it to the tuning circuit. The other capacitor plate is grounded to the capacitor body.


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 Post subject: Re: Turret tuner; What am I missing?
PostPosted: Dec Mon 02, 2019 5:18 pm 
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Not sure what that tuner is out of or exactly what it looks like assembled but some with a phenolic spiral like that had a lever riding on it that actuated a slug in and out of a coil.

If the set has a course fine tuning in the strip of each channel, you only plan to use ch3 or 4 and the fine tuning doesn't drift much with warmup you could just tweak a strips coarse fine tuning slug and ignore the missing parts as a workaround.


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 Post subject: Re: Turret tuner; What am I missing?
PostPosted: Dec Mon 02, 2019 6:51 pm 
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It's a standard coil turret tuner used in many sets. Here's a diagram.
The fine tuning is on the left. It's the spiral cut phenolic sliding between the grounded case and that insulated solder blob. Very simple arrangement.

If it isn't working, all I can figure is that the wire is disconnected from the local oscillator.

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 Post subject: Re: Turret tuner; What am I missing?
PostPosted: Dec Tue 03, 2019 6:50 am 
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Location: Belrose, NSW, Australia
Those phenolic cam fine tuning controls were quite common but didn't have a lot of range, especially on the Band 1 channels.

You'll need to set it to mid position and then adjust the brass slugs in the "biscuits" for each channel. When you have the slug set for edge of sound breakup, the fine tuning control will work.

Use a plastic tool for the slug adjustment. A large knitting needle, filed or ground down to a screwdriver flat, is the traditional tool for this job. Metal tools will affect the tuning.

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 Post subject: Re: Turret tuner; What am I missing?
PostPosted: Dec Wed 04, 2019 3:21 am 
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Joined: Nov Sun 04, 2007 6:01 am
Posts: 3400
Location: Redding, CA
The fine tuning control is working as described in prior posts. I did not recognise that it was working because it covers a very small range and the audio channel was not working. The audio problem was found to be a pinched, shorted wire from the tuner to the audio IF. After fixing the audio problem it is apparent that the fine tuning works. The set is an Admiral chassis 30B1.

Norman

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