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 Post subject: Lead weight over 12AT7 in GE 835
PostPosted: Nov Sat 11, 2017 7:57 pm 
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A note on the back of a 1950 GE 835 TV reads as follows: "Lead weight should be placed over 12AT7 - Tight Fit" The 12AT7 is the mixer/oscillator. The TV does not have this "weight"...does anyone know its purpose, its dimensions and if it is actually required.


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 Post subject: Re: Lead weight over 12AT7 in GE 835
PostPosted: Nov Sat 11, 2017 11:16 pm 
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RCA used them on the tuner in their early sets also. No doubt for interference protection, may not be as critical today since these sets are run off local sources like DVD. If it’s to stop internal interference then it might matter.


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 Post subject: Re: Lead weight over 12AT7 in GE 835
PostPosted: Nov Sat 11, 2017 11:46 pm 
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This pic show the Lead Shield over a Regular Shield that Eric was Describing.
it is heavy, and this is from a RCA Series set used in the Tuners , like the 630TS series

I wash my hands when ever I touch one :)

Terry


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 Post subject: Re: Lead weight over 12AT7 in GE 835
PostPosted: Nov Sat 11, 2017 11:47 pm 
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Lead shields were placed over tubes in an attempt to minimize microphonics from speaker audio.

- Leigh ]

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 Post subject: Re: Lead weight over 12AT7 in GE 835
PostPosted: Nov Sun 12, 2017 12:11 am 
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Leigh wrote:
Lead shields were placed over tubes in an attempt to minimize microphonics from speaker audio.

- Leigh ]

I never knew that !
thank you for the info Leigh

Terry


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 Post subject: Re: Lead weight over 12AT7 in GE 835
PostPosted: Nov Sun 12, 2017 6:36 pm 
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How much you need it depends on the particular 12AT7 in your set. Some are more prone to act like a microphone than others. You could do a quick test. With the set running and with the volume set to normal levels, gently tap on the tube with something made out of plastic. If you hear a noticeable sound from the speaker then you need the weight.

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 Post subject: Re: Lead weight over 12AT7 in GE 835
PostPosted: Nov Mon 13, 2017 8:01 am 
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Leigh wrote:
Lead shields were placed over tubes in an attempt to minimize microphonics from speaker audio.

- Leigh ]


That makes perfect sense since the speaker is mounted directly over the tuner on the RCA sets like the 630.


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