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 Post subject: Zenith Y723 Tracking Issue
PostPosted: Apr Mon 16, 2018 10:53 am 
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Location: Milford, PA
Hi,
I'm working on a Y723 Tabletop Zenith and having some issues with the tracking. The dial string was broken , which I replaced according to the Sam's Dial String Manual and since this set has no 600 padder, when setting the oscillator to 1600 kc, the tracking at the low end of the dial is off quite a bit. Is there a way to add more capacitance at the low end of the dial to correct this? I know that these are not precision sets, but when 1600 is good, 770 comes in at 810 kc!
Thanks

http://techpreservation.com/schematics/Zenith.htm

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 Post subject: Re: Zenith Y723 Tracking Issue
PostPosted: Apr Mon 16, 2018 3:20 pm 
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Location: Livermore, CA
Hi

Lowering the IF Frequency will spread out stations.

Could bend out the outer oscillator tuner plates. This will require the tuner to be closed further to receive lower frequency stations.

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 Post subject: Re: Zenith Y723 Tracking Issue
PostPosted: Apr Mon 16, 2018 4:44 pm 
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So what you're saying is if I lower the if freq a few kc, it will spread out the band? The other suggestion of bending the tabs on the oscillator I thought would reduce the capacitance and raise the freq when the plates were closed. Is that right?

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 Post subject: Re: Zenith Y723 Tracking Issue
PostPosted: Apr Mon 16, 2018 4:56 pm 
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Location: Livermore, CA
Bruce

Lowering the IF Frequency will spread out stations. Higher the oscillator frequency less capacity change is required to tune a range of frequencies. Lowering the osc takes more capacity change..

Bending plates out reduces overall capacity of the tuner section. This will require the tuner to be closed further to receive your station at 770. Lowering the point where it's received on the dial.

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 Post subject: Re: Zenith Y723 Tracking Issue
PostPosted: Apr Mon 16, 2018 5:33 pm 
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I had a similar issue. It turned out to be one of the low value capacitors in the converter circuit had drifted slightly. It was one of the non-paper capacitors I would normally leave alone.

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 Post subject: Re: Zenith Y723 Tracking Issue
PostPosted: Apr Mon 16, 2018 7:28 pm 
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Location: Milford, PA
Thanks for the replies. I'll try the bending the plates first. It's just such a pain, because you can't see where you are until putting the chassis back in the cabinet before putting the dial back on

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 Post subject: Re: Zenith Y723 Tracking Issue
PostPosted: Apr Tue 17, 2018 2:18 am 
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Joined: Jan Tue 16, 2007 7:02 am
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Location: Lexington, KY USA
Bruce,

Thanks for the link to a schematic!

The schematic appears to show the AM band oscillator coil, L4, to be adjustable. You might see if there is a threaded slug in there. That's the adjustment you would like to have for the low end of the AM band.

Barring a slug, you can still adjust the coil by use of a shorted turn, or a chunk of ferrite or powdered iron material. The shorted turn lowers the inductance, the magnetic core material will raise the inductance.

It sounds as if you need to reduce the coil's inductance.

Before doing anything drastic, you might try just moving the dial pointer. As long as you can still tune the entire band, you can get away with some adjustment of the pointer. No doubt the FM band will then have to be aligned to match. I think the FM band can be aligned at both ends of the band.

It's very likely that the loop antenna will also require alignment. Again, you can use the shorted turn or magnetic material tune it up or down a little, to see if it is resonating at the correct frequency.

If you are going to this much trouble, you really need to rig a temporary dial for use out of the cabinet.

Ted


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