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 Post subject: Should I pick up this Zenith Chassis?
PostPosted: Dec Mon 23, 2019 4:22 pm 
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A console MK2670 Chassis 12K25 just the audio chassis, looks complete for $35? Cabinet and speakers are gone.

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 Post subject: Re: Should I pick up this Zenith Chassis?
PostPosted: Dec Mon 23, 2019 4:45 pm 
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That depends upon whether you need it, or have plans for it.

Note that 12K25 is the tuner chassis, not the amplifier chassis which only has 7 tubes.

The matching 7K31 amplifier chassis uses EL84's in the outputs, so not high end in the audio realm, but high end for a consumer stereo console.

The 12K25 tuner chassis by itself without the amplifier is relatively worthless because it has no power supply, but gets its power from the audio amplifier chassis. In order to use it, you would need to build a power supply for it.

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 Post subject: Re: Should I pick up this Zenith Chassis?
PostPosted: Dec Mon 23, 2019 5:49 pm 
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Mr. Detrola wrote:
That depends upon whether you need it, or have plans for it.

Note that 12K25 is the tuner chassis, not the amplifier chassis which only has 7 tubes.

The matching 7K31 amplifier chassis uses EL84's in the outputs, so not high end in the audio realm, but high end for a consumer stereo console.

The 12K25 tuner chassis by itself without the amplifier is relatively worthless because it has no power supply, but gets its power from the audio amplifier chassis. In order to use it, you would need to build a power supply for it.


Ahhh, didn't realize that the amp is separate, thanks for the info!

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 Post subject: Re: Should I pick up this Zenith Chassis?
PostPosted: Dec Mon 30, 2019 3:20 pm 
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If that is a FM stereo tuner chassis, it would be easy enough to build a power supply for it and buffer the output with OP-AMPs so you can connect it to any amplifier modern or vintage.


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 Post subject: Re: Should I pick up this Zenith Chassis?
PostPosted: Dec Mon 30, 2019 7:04 pm 
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Tube Radio wrote:
If that is a FM stereo tuner chassis, it would be easy enough to build a power supply for it and buffer the output with OP-AMPs so you can connect it to any amplifier modern or vintage.
... or, if mono, add a cathode follower tube for audio output, e.g. 6C4 (need to add a new base) - if stereo, need two (use a double triode.) This would feed any low-Z s/s amplifier input.
Cheers,
Roger

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 Post subject: Re: Should I pick up this Zenith Chassis?
PostPosted: Dec Mon 30, 2019 8:07 pm 
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Agreed and I personally would prefer a tube, but the tube would not be quite as easy to implement.

An OP-AMP could be implemented as easily as two diodes, two filter caps and two 1M-4.7M resistors.

The diodes and filter caps provide a +/- supply so that the OP-AMP does not need to be biased and does not need a coupling capacitor on its output. The resistors serve to give the + OP-AMP input a reference to grounds as the existing tuner circuitry is most likely cap coupled to its output.


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