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 Post subject: Please, where do I connect this cable?
PostPosted: Apr Wed 08, 2020 3:24 am 
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Joined: Apr Wed 08, 2020 2:17 am
Posts: 4
Dear Friends:

First of all, sorry for my English; it is very bad.

I am restoring a Graetz Melodia 1118 radio. I am redoing the power supply with new components. But in the power transformer I find a cable that I don't know where to connect.

I show you the schematic diagram so you can help me.

Does it connect to ground? At what point?

Does it connect to earth? But the radio doesn't have a eart wire.

Thanks for the help you can give me.

A cordial greeting,

Sebastián


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 Post subject: Re: Please, where do I connect this cable?
PostPosted: Apr Wed 08, 2020 4:14 am 
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Joined: Dec Sat 28, 2019 4:18 pm
Posts: 273
Location: Corinth, TX
Not certain, but it looks like that wire should go to chassis ground like the PS filter caps.

John


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 Post subject: Re: Please, where do I connect this cable?
PostPosted: Apr Wed 08, 2020 4:24 am 
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Joined: Dec Wed 25, 2013 7:57 am
Posts: 4446
Location: USA
Yes, it is the metal chassis.

If you are familiar with other symbols, it is the same as this:
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or this
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2.jpg
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blue.jpg
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 Post subject: Re: Please, where do I connect this cable?
PostPosted: Apr Wed 08, 2020 5:21 am 
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Joined: Apr Wed 08, 2020 2:17 am
Posts: 4
Thank you for your answers!

It is a blue wire that seems to come out of the transformer core (according to the diagram).

I hesitated because there is also a ground symbol on the primary side of the transformer.

That ground symbol is the only one used in the entire radio circuit as a signal ground too.

I didn't want to break anything, so I asked.

Thank you!


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 Post subject: Re: Please, where do I connect this cable?
PostPosted: Apr Wed 08, 2020 5:43 am 
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Joined: May Tue 30, 2006 4:46 pm
Posts: 9936
Location: Santa Rosa, CA
This is called a Faraday shield and reduces noise coupling between primary and secondary windings of transformer.


Image

Rich


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 Post subject: Re: Please, where do I connect this cable?
PostPosted: Apr Wed 08, 2020 6:20 am 
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Joined: Apr Wed 08, 2020 2:17 am
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Thank you very much, Rich!

So should I connect that wire to safety ground? that is, the green-yellow wire from the outlet? But the radio has no safety ground.

Can I then connect it to the ground of the filter capacitors of the power supply?

Thank you!


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 Post subject: Re: Please, where do I connect this cable?
PostPosted: Apr Wed 08, 2020 5:22 pm 
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Joined: Dec Wed 25, 2013 7:57 am
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Location: USA
Not electrical safety ground. Radio ground (blue).


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 Post subject: Re: Please, where do I connect this cable?
PostPosted: Apr Wed 08, 2020 7:52 pm 
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Joined: Apr Wed 08, 2020 2:17 am
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Thank you very much, AJJ! I will do it.


Greetings,

Sebastián


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