View Full Version : (circa 1946) ZENITH S-11680 Intermixer w/Cobra...


SixCats!
06-28-2007, 07:11 PM
Hi all,

I am planning to buy a Zenith S-11680 Intermixer Automatic Record Changer which has the CORBRA tone arm. I only had a brief look at this unit today which also has FM. From what I could tell, there appears to be only one (either) ten or twelve inch Field Coil speaker. I suspect this unit must be a mono PP tube Amp. The Cabinet is in BEAUTIFUL condition and is quite fancy! I thought the Record Player was very neat the way it is
"pinned/higned" and "rotates out" to the play position. Of course, I realized that due to it's age, this unit is going to need some work to get her up to spec. Lucky for me, I happen to know a man who is a MASTER at repairing these old Antique Radios (and who's prices are VERY reasonable). That being said, Old Antique Radios is pretty much new territory for me. Might anybody have any experience with this old unit ? I think once this unit is "up and running" it going to be a real show piece! Thanks for any help.

Regards,
SixCats!

Chad Hauris
06-28-2007, 08:29 PM
Your Zenith will be a 78-rpm only record changer. There were later Cobra units built that can play 33 and 45 but the Cobra should only be used on mono records. The wider stylus will destroy stereo records.
Also, I have found that the Cobra cartridge works well for 78's but does not have the frequency response and stylus compliance for high fidelity reproduction of microgroove records.
We have replaced several Wurlitzer jukebox Cobra cartridges in 45 RPM machines with a magnetic cartridge/preamp and the sound quality is much improved.

mr_fixer
07-23-2007, 05:29 PM
No! Don't do it! replace a zenith cobra cartridge with magnetic? you just need the right sized needle. there are people on the web, who have gazillions of vintage needles. I bought 2 for my Zenith S-9010, a .5 mil for lp's and 1.0 for 78's I think it was about $20 for the pair. Now I'm not going to be playing any rare audiophile discs on it. Thats what the my other turntables are for. these are for nostalgic records which are cheap at any thrift store. Just my 2 cents worth. Logan

Randy Bassham
07-24-2007, 06:48 AM
I believe the sizes are 1 mil for LP/45's and 3 mil for 78's. The early Zenith "Radionic" pickups for the Cobra turntables did not generate a voltage, the needle was connected to a small round disk that was put directly in front of a coil of wire that was in the circuit of an oscillator. The movement of the disk changed the "Q" of the coil and varied the output amplitude of the oscillator, which was detected by the second half of the "Radionic" tube, in my 12H094 I believe it's a 7H7 dual triode. The output of the detector is fed into the amplifier of the radio. It's quite a circuit and as Chad says it works quite well for 78's. The 3 mil "Red" cartridges are getting hard to find and commonly what you will find are the 2 mil "Red/Green's" that were sold as all speed but I don't think they sound as good. The "Green" cartridges were 1 mil for Microgroove records LP's and 45's.

There was a later version of the Radionic cartridge that was used in monaural sets but when Stereo came in the design was apparently not suited to Stereo, and Zenith continued to use the tone arm with the little eyes but they had conventional crystal/ceramic pickups usually with Voice of Music supplied turntables.

Chip - HP
07-24-2007, 08:24 AM
Is there more than one FM band on the radio? ... for a couple of years (in the late '40s), there were two FM bands ...

Randy Bassham
07-24-2007, 08:39 AM
Is there more than one FM band on the radio? ... for a couple of years (in the late '40s), there were two FM bands ...

Yes, it has 42-50 Mhz as well as 88-108. Not much to listen to on the lo band. I can pick up the Highway Patrol on it here since they are on 42.920 but since they are narrowbanded the volume is quite low. I was the Field Engineer for the Highway Patrol in Southern Missouri until April 1 when I retired. Also a local concrete company and an electric Co-op are still running lo band but their transmissions are very infrequent. I've also got the Zenith Major which as I understand was Zenith's first post war table model FM set and was named the Major is honor of Major E H Armstrong, the set has a sticker on the back stating it uses the "Armstrong System", my collection includes a couple of General Electric AM-FM sets that have the same sticker on them. The Zenith Major has both FM bands also.