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 Post subject: Re: Zenith S-7000 Wireless and a 1.63 MHz Crystal
PostPosted: Jun Wed 24, 2020 1:45 am 
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Posts: 4140
pharrison wrote:
Hi,

Would anyone recommend installing a 1 to 1 input transformer for the electric mains for safety?


Yes. In a pinch you can use back to back power transformers of the same voltage rating.

And when you get this running, please report on it. I've heard this circuit denigrated since I joined this forum. I've never heard why it's so unsatisfactory. So I'm curious. Let us know.


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 Post subject: Re: Zenith S-7000 Wireless and a 1.63 MHz Crystal
PostPosted: Jun Wed 24, 2020 3:35 pm 
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Thanks!

That's makes me possibly to not want to try it.

Does anyone have a picture of this Zenith device?


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 Post subject: Re: Zenith S-7000 Wireless and a 1.63 MHz Crystal
PostPosted: Jun Wed 24, 2020 5:18 pm 
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Build this one, will annihilate the phono osc.

You'll need a 120v P/S that isn't pictured.


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 Post subject: Re: Zenith S-7000 Wireless and a 1.63 MHz Crystal
PostPosted: Jun Wed 24, 2020 5:58 pm 
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Thank-you Tom!


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 Post subject: Re: Zenith S-7000 Wireless and a 1.63 MHz Crystal
PostPosted: Jun Thu 25, 2020 7:30 am 
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Joined: Jan Tue 16, 2007 7:02 am
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Location: Lexington, KY USA
To "recap", the Zenith sort of phono oscillator does work. I had one as a kid. It just doesn't work as well as other alternatives.

You have already brought up one of the shortcomings, and that is the lack of isolation from the AC line.

It can't provide much modulation percentage. The remote cutoff audio grid causes audio distortion. The basic circuit may need a high output phono cartridge even to get moderate modulation. And on and on.

If you have already gathered up all the parts, I'd say go ahead and build it. But if the time and money has not already been spent, you might try one of the other designs.

Ted


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 Post subject: Re: Zenith S-7000 Wireless and a 1.63 MHz Crystal
PostPosted: Jun Thu 25, 2020 3:49 pm 
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Ted,

Yes, I think I will consider alternatives.

Regards,

ph


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 Post subject: Re: Zenith S-7000 Wireless and a 1.63 MHz Crystal
PostPosted: Jun Thu 25, 2020 4:48 pm 
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The one Tom posted above has one of the highest ratings among the community members. Mine works well. Here's a photo.


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 Post subject: Re: Zenith S-7000 Wireless and a 1.63 MHz Crystal
PostPosted: Jun Thu 25, 2020 6:10 pm 
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That's beautiful!

So you put a 1:1 power transformer in the circuit.

Any inside pics?


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 Post subject: Re: Zenith S-7000 Wireless and a 1.63 MHz Crystal
PostPosted: Jun Thu 25, 2020 9:23 pm 
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Here is Norm's text that went along with his schematic above that Tom posted.


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 Post subject: Re: Zenith S-7000 Wireless and a 1.63 MHz Crystal
PostPosted: Jun Fri 26, 2020 1:17 am 
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Thanks Mike, I don't seem to have the orig instructions.

Power supply can be modeled after this version of 6888. Had transformer on hand, so what I used.


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 Post subject: Re: Zenith S-7000 Wireless and a 1.63 MHz Crystal
PostPosted: Jun Fri 26, 2020 5:51 am 
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pharrison wrote:
That's beautiful!

So you put a 1:1 power transformer in the circuit.

Any inside pics?


The transformer you see is a regular filament transformer. A duplicate is underneath the chassis, so the two back to back form a 1:1 (almost) transformer.

Sorry, I took no inside pics. I don't want to take it apart to take photos because there are three layers of perfboard separated by spacers. I had to do this to fit everything in. Because it's three stories inside, there's not much on each story, and the transformer take up much of that space, so you're not missing much. Glad you like it, though.


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 Post subject: Re: Zenith S-7000 Wireless and a 1.63 MHz Crystal
PostPosted: Jun Sun 28, 2020 4:03 pm 
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Location: Beaver Falls, PA. USA
Absolutely use an isolation transformer with the Zenith circuit. However, there are much better designs out there; the 6888 works very well.

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