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 Post subject: Zenith C845Y, Chassis 8C02 variations, R32?
PostPosted: Mar Sun 02, 2014 10:38 pm 
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Location: Mission Viejo, southern California
I've got two of these radios, one with a blonde cabinet, Model C845E, serial number 8527462, and a black one, Model C845Y, serial number 8842077. If those serial numbers are sequential, they made a bunch of them! Both chassis are stamped 8C02.

The RM and Tech Preservation schematics match the earlier serial number, but the black C845Y has the following interesting changes:

1) R32 is not 2,200 ohms. It is overheated in the center, but the first band is green, for 5, and the last silver. The optional capacitor bridging it is present, and is 0.0033mfd. It measures 400-some ohms. Do you think it should be a 500-ohn unit?

2) C34 is 0.47 mfd, not 0.1 mfd (yes, it clearly was original)

3) Instead of a 100K resistor across C34, there is a 22K resistor

4) The resistor from the bottom of the tone control is 27 ohms, not 100 ohms

5) The capacitor after the above unnumbered resistor and to ground is 0.33 mfd , rather than 0.47 mfd

6) R31, at the bottom of the volume control, is 82 ohms, not 1,000 ohms.

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 Post subject: Re: Zenith C845Y, Chassis 8C02 variations, R32?
PostPosted: Mar Mon 03, 2014 8:53 pm 
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The sound is distorted, unless the tone conyrol is set all of the way to treble. I tried using the speakerd from my other radio with the same chassis, and it is the same. I also tried a CD player input to the AUX jack, and it is the same. That narrows it down to the audio section. There do not seem any schematics of the variation I have.

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 Post subject: Re: Zenith C845Y, Chassis 8C02 variations, R32?
PostPosted: Mar Tue 04, 2014 2:26 am 
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Location: Mission Viejo, southern California
Nobody has any thoughts?

I've discovered that the audio system changes I outlined above were made to Chassis 8X02 used in the final version of this radio, the Model X337, except that the resistor parallel to the 0.0033 mfd capacitor on the green wire (feedback) from the output transformer is 680 ohms.

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