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Old 05-10-2016, 10:03 AM
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Zenith X426 AM/FM radio

I finally found one of these Zenith table radios (an X - 1967 model) with the transistor socket chassis (8NT21). The only thing wrong with it was a bad coupling capacitor going into the volume control. Now it works good, on both AM and FM. If anyone has that tuning knob I'm missing - let me know? Here's the pics...
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File Type: jpg 67zen2.jpg (59.0 KB, 41 views)
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Old 05-10-2016, 10:47 AM
dieseljeep dieseljeep is offline
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Originally Posted by Adam View Post
I finally found one of these Zenith table radios (an X - 1967 model) with the transistor socket chassis (8NT21). The only thing wrong with it was a bad coupling capacitor going into the volume control. Now it works good, on both AM and FM. If anyone has that tuning knob I'm missing - let me know? Here's the pics...
That is one well-built solid state radio! Even uses the standard size IF transformers. Very few import parts used!
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Old 05-10-2016, 01:21 PM
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Originally Posted by dieseljeep View Post
That is one well-built solid state radio! Even uses the standard size IF transformers. Very few import parts used!
Not only that, but this one has the permeability-tuned FM tuner. I thought it would after I saw the linear FM tuning scale, so I wasn't surprised when I saw the tuner under the chassis. The other interesting thing (to me, anyway) about this radio is the unique dial drive system, which tunes AM and FM simultaneously. The only thing I don't like about that design is just that, i.e. the AM and FM dials move together when you turn the tuning knob. I have a feeling this might have been a cost-cutting measure by Zenith in the late '60s, so they didn't have to use a separate dial drive and tuning knob for each band. The only FM tuners I ever saw with such a tuning arrangement (separate dial drives for AM and FM) were the ones that were designed for the old AM-FM stereo broadcast standard, which of course was abandoned when multiplexed FM broadcasting became the new standard for stereo FM.

Another cost-cutting feature was the lack of a tweeter speaker, as was used in the early '60s Zenith radios; at least I didn't see a separate tweeter in this one. The large pulley driving the dial cord is in the position where I would have expected to see such a speaker. The only thing I can think of that would have prompted Zenith to design these late '60s radios without tweeters is the solid-state design; the audio output transistor may not have been powerful enough to drive the main speaker and a tweeter as well. The earlier Zeniths with tweeters (K731, C845, et al.) drove them directly from the plate of the audio output tube.
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Last edited by Jeffhs; 05-10-2016 at 01:32 PM.
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Old 05-10-2016, 01:46 PM
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Originally Posted by Jeffhs View Post
Not only that, but this one has the permeability-tuned FM tuner. I thought it would after I saw the linear FM tuning scale, so I wasn't surprised when I saw the tuner under the chassis. The other interesting thing (to me, anyway) about this radio is the unique dial drive system, which tunes AM and FM simultaneously. The only thing I don't like about that design is just that, i.e. the AM and FM dials move together when you turn the tuning knob. I have a feeling this might have been a cost-cutting measure by Zenith in the late '60s, so they didn't have to use a separate dial drive and tuning knob for each band. The only FM tuners I ever saw with such a tuning arrangement (separate dial drives for AM and FM) were the ones that were designed for the old AM-FM stereo broadcast standard, which of course was abandoned when multiplexed FM broadcasting became the new standard for stereo FM.

Another cost-cutting feature was the lack of a tweeter speaker, as was used in the early '60s Zenith radios; at least I didn't see a separate tweeter in this one. The large pulley driving the dial cord is in the position where I would have expected to see such a speaker. The only thing I can think of that would have prompted Zenith to design these late '60s radios without tweeters is the solid-state design; the audio output transistor may not have been powerful enough to drive the main speaker and a tweeter as well. The earlier Zeniths with tweeters (K731, C845, et al.) drove them directly from the plate of the audio output tube.
The electrostatic tweeters needed high voltage to run which the transistor stage may not have been capable of.

Grundig had an non-simulcast system with separate dial strings and a single knob (most european makers used concentric knobs on dual string tuners) with a clutch mechanism linked to the band switch that would swithc which string the knob drove based on the band selected. I had an SO-205-U console with that tuning mech and it was a total cluster f^ck.
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Old 05-17-2016, 06:44 PM
Captainclock Captainclock is offline
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Quote:
Originally Posted by Jeffhs View Post
Not only that, but this one has the permeability-tuned FM tuner. I thought it would after I saw the linear FM tuning scale, so I wasn't surprised when I saw the tuner under the chassis. The other interesting thing (to me, anyway) about this radio is the unique dial drive system, which tunes AM and FM simultaneously. The only thing I don't like about that design is just that, i.e. the AM and FM dials move together when you turn the tuning knob. I have a feeling this might have been a cost-cutting measure by Zenith in the late '60s, so they didn't have to use a separate dial drive and tuning knob for each band. The only FM tuners I ever saw with such a tuning arrangement (separate dial drives for AM and FM) were the ones that were designed for the old AM-FM stereo broadcast standard, which of course was abandoned when multiplexed FM broadcasting became the new standard for stereo FM.

Another cost-cutting feature was the lack of a tweeter speaker, as was used in the early '60s Zenith radios; at least I didn't see a separate tweeter in this one. The large pulley driving the dial cord is in the position where I would have expected to see such a speaker. The only thing I can think of that would have prompted Zenith to design these late '60s radios without tweeters is the solid-state design; the audio output transistor may not have been powerful enough to drive the main speaker and a tweeter as well. The earlier Zeniths with tweeters (K731, C845, et al.) drove them directly from the plate of the audio output tube.
I have a Solid State Motorola AM/FM Stereo Table Radio from about 1963 or 1964 that has a tuner with both AM and FM Dials being tuned together simultaneously and its actually a pretty decent unit sensitivity wise and sound wise I don't think it was a cost cutting measure at all, I think it was just a way to simplify the design process so that you used as few parts as possible given the limited space you had to work with, because with a smaller Tabletop radio it would be harder to fit 2 seperate tuner knob and pulley systems into a cabinet as small as the one that this Zenith has or my Motorola has. I don't think that the double ganged tuner system like this Zenith or my Motorola uses necessarily makes it a worse product than a unit that uses two seperate tuner knobs, in fact my Motorola stereo has excellent sensitivity and selectivity even in spite of the single knob tuned dual ganged tuner dial mechanism.
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