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Zenith Cobra Tone Arm And Pickup

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Zenith Cobra tone arm and pickup

Postby George in Georgia » 17 Jan 2010 23:05

The post about the Stax and Weathers pickups jogged my memory.
When my sister was born in 1948 my father splurged with the tax deduction and bought a Zenith table "hifi" with am, fm, 78 rpm and the then new 33 rpm.
The auto changer had 2 tone arms, one in maroon for auto changer play of 78s and a second green arm for manual play of 33s. The pickup was a tiny thing about 1/4 wide by 1/2 long by maybe 3/32 thick and very light. It plugged into electrical contacts in the arm. Since the stylus 3 mil for 78, 1 mil for 33 was integral to the pickup we had old worn ones sitting around. Out of curiousity we split one open. Very little to see, the stylus attached to - as I remember - a tiny circular piece of metal adjacent to a tiny coil. I just Googled "Zenith Cobra arm" and found this:

"Radionic" phono circuit
The schematic for this set shows a 6J5 tube as "phono oscillator". Apparently the Zenith Radionic Cobra cartridges vary the "Q" of a tiny inductor to modulate a 2.5 MHz oscillator. This is fed directly to the receiver which detects and amplifies the signal. Unusual to say the least.

So the circular metal plate and coil formed the inductor. It would seem that the potential was there for a low mass, light tracking device - but it wasn't so!

Didn't Weathers also produce turntables? Perhaps also satellite speakers disguised as books and a small common woofer? There were such wonders in the Allied Radio and Lafayette catalogs, back in the day!
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Postby Chiltern » 22 Jan 2010 18:04

Hi, anyone familiar with Wurlitzer Jukeboxes of that era, from the model 1100 (24 x 78 rpm) thro to the mono 2400 (100 x 45rpm) of 1960 will know the pitfalls of this system.

Hard on records and difficult to get to sound right. Often a number of new cartridges would have to be tried until one worked OK. Hopeless of course on any Stereo 45's, no vertical compliance at all.

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Postby Whitneyville » 09 Feb 2010 08:11

I have my older sister's 1950 Zenith Cobra-Matic AM radio/phonograph with the red/green stylus like you meantion. Can I post photos directly on here or do they have to be "hosted"? (I have Snap-Fish for my Fuji DSLR) Now my Grandmother had a dark maroon 100% Bakelite cased late 50's Zenith Cobra-Matic (my Uncle "approprated" it when I bought my grandparent's house and "contents" that he didn't want!). So pre-transitor radio/cars with fins cooool! 8)
My sister's is fabric covered bent plywood "doped" in a sort of mustard yellow with some olive green horizontal stripes across the front. Very "post WWII". Still plays fine, but the Neddle Dr. is gonna get some $$ for a new cart/stylus while they're still made.
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Postby Vulcan Viewer » 09 Feb 2010 10:20

You can host on here. Checkout the Gallery link at the top of the page. When a picture is in the gallery you will see a tag you can copy and use within your posts.
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