Author Topic: 1962 Magnavox Astrosonic Stereo Theatre  (Read 3676 times)

PanAm

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Re: 1962 Magnavox Astrosonic Stereo Theatre
« Reply #15 on: July 27, 2017, 10:09:43 AM »
I know I probably seem annoying, but I have no idea what a 6EU7 is. Could I just take a picture of the components inside the console and then post them and then you can point them out individually? I have no background in electronics and I'm trying to save a buck and get this right channel to work so I don't have to have it repaired.

Bill

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Re: 1962 Magnavox Astrosonic Stereo Theatre
« Reply #16 on: July 31, 2017, 11:44:07 AM »
6EU7 is a tube.  It's one of the smaller ones with the small pins.  Pictures are always good.

Bill

Motorola Minion

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Re: 1962 Magnavox Astrosonic Stereo Theatre
« Reply #17 on: July 31, 2017, 12:02:08 PM »

If yours has 6EU7 preamp tubes instead of the standard 12AX7, that is THE last all-tube console.

If it is like my Normandy Symphony of the same year, the tuner is a 79-series and your amp is a 9300-xx series. The four output tubes would be 6BQ5 then. You also might have the separate multiplex adapter as well. A very interesting combo, and probably has the horns instead of the pair of cone speakers.

Get inside this thing and wiggle the tubes a bit. I had to replace a bad tube socket in mine.
Tubes - Magical - Tubes

Dave

PanAm

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Re: 1962 Magnavox Astrosonic Stereo Theatre
« Reply #18 on: August 05, 2017, 12:22:17 PM »
Thanks for your suggestions. I will get inside it soon to troubleshoot and take some photos.

PanAm

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Re: 1962 Magnavox Astrosonic Stereo Theatre
« Reply #19 on: August 11, 2017, 11:32:00 AM »
Haven't had time to get inside yet, but I did look through the ventilation holes on the tuner side and I saw what looked like amber colored glass on the floor. Is it possible something exploded and that's why I am not getting sound from the right channel?

TC Chris

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Re: 1962 Magnavox Astrosonic Stereo Theatre
« Reply #20 on: August 11, 2017, 05:10:42 PM »
The usual reply to "is it possible?" questions is "anything's possible."  It's really easy to get the backs off, and then you can see what's actually happening.  Sometimes a tube that has lost vacuum (cracks, etc.) may show some orange-ish color.  But really, guessing at what might be wrong doesn't really get you anywhere.  Open it up and have a look-see.

Chris Campbell

PanAm

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Re: 1962 Magnavox Astrosonic Stereo Theatre
« Reply #21 on: August 11, 2017, 05:55:40 PM »
It will definitely happen within the next week.

PanAm

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Re: 1962 Magnavox Astrosonic Stereo Theatre
« Reply #22 on: August 14, 2017, 08:16:53 AM »
Here's the pictures of the inside. Let me know if there is anything visibly wrong that would cause the right channel not to have sound or if you have trouble viewing.

PanAm

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Re: 1962 Magnavox Astrosonic Stereo Theatre
« Reply #23 on: August 14, 2017, 08:19:23 AM »
Some more:

electra225

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Re: 1962 Magnavox Astrosonic Stereo Theatre
« Reply #24 on: August 14, 2017, 09:14:49 AM »
Check or replace V3, the 6EU7 in the tuner.  6EU7's came out in the 1961 models of the 8800 and 9300 series of amps and their corresponding tuners.  Magnavox used the 6EU7 twin-triode due to its low-noise characteristics.  They tend to short cathode to filament and one half tends to die.  I have found the 6EU7 problematic and is always a suspect when I encounter a performance problem.  It is entirely possible that one half of that tube is dead, causing the dead channel.  This is only a "guesstimation", based on experience, since I have not laid eyes on your instrument.  Also suspect control switches of being electrically "dirty" such as the function switch and the external speaker switch.  There are two 6EU7's in the amp, these should be tested and subbed for the same reasons noted above.  A schematic and directed electrical testing, guided by a schematic, is your best procedure for troubleshooting.  Good luck.

Look on the diagram you posted for locations of the 6EU7's. 
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PanAm

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Re: 1962 Magnavox Astrosonic Stereo Theatre
« Reply #25 on: August 14, 2017, 12:15:39 PM »
Thanks for your input. I don't have a tube tester and I don't really want to mess around with testing them so I will probably end up buying new 6EU7s. You previously mentioned DeOxit. Is there an acceptable substitute for it that I can buy at the store or is my best bet just to buy the brand name?

TC Chris

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Re: 1962 Magnavox Astrosonic Stereo Theatre
« Reply #26 on: August 14, 2017, 07:24:53 PM »
Here's the pictures of the inside. Let me know if there is anything visibly wrong that would cause the right channel not to have sound or if you have trouble viewing.

The 5th photo down shows a press-on connector--the kind often used for speakers--that is not pressed on to anything.  Maybe a speaker lead is disconnected?  Can't tell from the photo.

Chris Campbell

TC Chris

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Re: 1962 Magnavox Astrosonic Stereo Theatre
« Reply #27 on: August 14, 2017, 07:26:33 PM »
Some more:

Last photo here--TWO connectors not connected.

Chris Campbell

electra225

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Re: 1962 Magnavox Astrosonic Stereo Theatre
« Reply #28 on: August 14, 2017, 09:10:21 PM »
I saw the disconnected wire and thought it might be a wire for the AM antenna.  It has to be disconnected to remove the back.  It is a black wire.  If that black wire was disconnected from the amplifier, all the speakers would be dead.  I can't see the speaker wires well enough in the photos to really tell.  I have been wrong before.  Naturally, if a wire is disconnected, that would be a problem.  The FM antenna uses twin lead.  Good call, Chris.
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PanAm

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Re: 1962 Magnavox Astrosonic Stereo Theatre
« Reply #29 on: August 15, 2017, 12:10:03 PM »
Here are some pictures of those disconnected black wires. They were either disconnected when I bought the unit or I accidentally disconnected them when I removerd the back. I have no idea what they plug into. Also included are pictures of the speaker connections.