Vintage Magnavox Astro-Sonic

Discussion in 'Turntables' started by Hale, Jan 4, 2019.

  1. Hale

    Hale New Member

    Messages:
    10
    Location:
    Kentucky
    I have an early / mid-60's Magnavox Astro Sonic console (not sure of the date) that I inherited and have attempted to perform some basic maintenance on - at least to the extent of my abilities - but cannot get the turntable to spin properly. It plays, but the tempo is slower than it should be and rhythmic, slow warble continues when a record is played which never seems to get to the appropriate speed.

    To date, I have used De-Oxit to all dials (which worked great for the FM tuner / volume, etc), relubed most every component to theturntable, and buffed / cleaned all accessible rubber wheels to assure good contact. I am suspicious that the problem lies in an electrical issue and do not know where to begin with repairs without first diagnosing the problem...this is where I could use some help.

    I have a manual but it doesn't list any electronic components. I have however attached for reference the electrical diagram contained on the bottom panel within the console. Through some online research, I have found some discussions about similar Astro Sonic consoles having capacitors that eventually go bad and need replaced. And I would suspect that a unit, which is in it's mid-50's, would have some electronics beginning to fail that would need replaced - I just don't know what to replace!

    I have attached several images for reference and would appreciate any guidance or recommendations to help me troubleshoot the issue...

    Stereo.jpg Turntable.jpg Model 2ST697.jpg Electrical Diagram.jpg Amplifier.jpg
     

     

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  2. M Chavez

    M Chavez Active Member

    Messages:
    318
    Plug the turntable into a wall outlet and play a record
    If the problem is still there then you know where it is
    This assuming it is the music on the record warbling and not a warble tone ON TOP of everything
     
  3. sgmlaw

    sgmlaw Well-Known Member

    Messages:
    650
    I’ve actually rebuilt a few of those. If this has an unknown service history, chances are the lube in the main bearing has dried and tightened up free rotation. The other issue is a hard or dirty idler wheel making uneven traction.

    If you can get it out of the cabinet, most of the time if you relubricate the main bearing and clean the idler wheel and inner platter rim, it comes back pretty solid.

    You have a SS amp chassis there. That should probably be completely recapped at this point. The tuner/preamp subchassis, too. My recollection is that the original outputs were germaniums, and those are more fragile and less tolerant of failing operating values than the silicon ones are.

    There used to be a Yahoo group dedicated to the preservation of Magnavox consoles, and they had plenty of schematics for every model.

    The last SS Maggie console I rebuilt was 6 or 8 years ago, so I don’t know if those resources are still available. All I remember most from that job is that the IF cans in the Tuner/Preamp chassis on these aren’t that durable, and that the mica cap on several had corroded away.

    Everyone chases the earlier tubed chassis models on these. But the early SS models actually aren’t that bad sounding. Again, recap this to see what it really sounds like.

    Leave the speakers be. They are horns and paper surround woofers, and should last forever if undamaged. One of the paper crossover caps on this last one I did looked like it had suffered water damage at some point, so I recapped both sides with modest films. No change in sonics, which indicates that the original Xofers on these are fairly enduring, too.

    I may have some pix of that last job, as it was for a family member and I usually give a pictorial if it’s for someone special. If I do, I’ll post them later so you can see what you are getting into.

    Good luck!
     
    Last edited: Jan 4, 2019
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  4. Hale

    Hale New Member

    Messages:
    10
    Location:
    Kentucky
    sgmlaw - I appreciate the response. You've included some good information. If you think the rebuild you documented 6 or 8 yrs ago is relevant and are able to find record of it, I'd like to see it...

    The speakers are in relatively good condition from what I can tell - to summarize: the radio tuner works well and it projects a lot of sound!

    I had already attempted to lube every accessible component (with sewing machine oil) after removing the platter. I had also removed the idler wheel, buffing it along the perimeter with an emery board to remove hardened rubber (in an attempt to improve grip / traction), and lubed it as well. None of this seemed to improve the "warbling" effect when playing a record. My next course of action will be to revisit the main bearing...and I'll document / report findings afterward.

    You clearly know a great deal about the inner workings of the console, but the following is completely foreign to me:
     
  5. JFRACE

    JFRACE AK Subscriber Subscriber

    Messages:
    1,020
    Location:
    New Jersey
    The warbling can go away if you play it long enough, that would also indicate the main bearing or missed spots use alvania or
    Lithium grease on the contacts and lighter oil on the idler joints. Facebook has 4 to 5 pages you can join for help. Just punch in magnavox consoles. I had the same issue on my Maggie and did the above and it fixed it. Recap definitely needs to be done at this point.
     
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  6. Hale

    Hale New Member

    Messages:
    10
    Location:
    Kentucky
    I have thoroughly cleaned the main bearing and relubed with lithium grease and there is no change in the wavering sound. Sounds like a Recap would be the next step...?!?

    Hate to be a newb, but is there a procedure available for this console (or one similar) that someone could point me toward?
     

     

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  7. Hale

    Hale New Member

    Messages:
    10
    Location:
    Kentucky
    The model numbers for both the tuner and the amplifier chassis are as follows (and as shown in the attached photos).

    Tuner: R20801
    Amp Chassis: A55104​

    Can anyone help identify which eletronic components would likely need replaced to prevent the warbling affect on the turntable?

    Does anyone have schematic diagrams available?

    Thanks in advance...

    Amp Chassis.jpg Tuner.jpg
     
  8. charlesdemar

    charlesdemar AK Subscriber Subscriber

    Messages:
    122
    Have you taken the motor apart, properly cleaned the bearings, re-oiled and re-aligned the motor correctly? I would expect it to be a motor problem, if the idler wheel isn't slipping. These turntables motors run off line voltage. Capacitors would affect the sound, but not the speed of the turntable.
     
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  9. Hale

    Hale New Member

    Messages:
    10
    Location:
    Kentucky
    With relative confidence, I can say that the idler wheel isn't slipping. Additionally, I have cleaned / lubed everything that's accessible without removing the base plate - this includes the main turntable thrust bearing. However, I do not know the process to re-align the motor as mentioned - but I like the recommendation and it sounds like this should be performed. Please let me know what to do / how to perform this work.

    Many thanks...
     
  10. MarcoFantone

    MarcoFantone New Member

    Messages:
    27
    Hale:
    Welcome to the forums. Our Astro-Sonics were built a month from each other! (I saw the 10/64 sticker on one of your image posts). Not sure I can speak to your specific problem but removing the turntable from the console is definitely a must in order to be able to access the underside. From what I could tell, the turntable is nearly 100% mechanical except for the motor that runs the turntable speeds. This means that there are so many parts that are capable of creating friction that may reduce the speed of the platter. If you haven't removed the base plate, I'd certainly do that just to check that off as a possible problem area. I saw the post about re-aligning the motor but don't know exactly what that requires. Best of luck; the console appears to be in fantastic condition!
     
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  11. Hale

    Hale New Member

    Messages:
    10
    Location:
    Kentucky
    MarcoFantone - thanks for the welcome. Seems like these were popular devices back in the day...and it's cool to know there are many people interested in preserving them.

    Cosmetically, the console is in great condition. The turntable has me befuddled, but I'm determined to get it working - then I'll focus on the speakers: both sides project sound, but one side (facing / left) is a bit "dim" by comparison.
     

     

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  12. JFRACE

    JFRACE AK Subscriber Subscriber

    Messages:
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    Location:
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    As some have stated above, the table needs to be taken out and worked in all start levers and mechanics need to be cleaned and then re lubed on top of the main bearing area and cam. Any old lube will hinder proper operation.
     
  13. Hale

    Hale New Member

    Messages:
    10
    Location:
    Kentucky
    Alright - will remove the table this weekend and clean more thoroughly.
     
  14. Hale

    Hale New Member

    Messages:
    10
    Location:
    Kentucky
    After removing the turntable, cleaning & relubing all mechanical components that could affect record speed (idler wheel, spindle, platter, etc) to the best of my abilities, and then reassembling, I am frustrated to report that there is no change to the sound. The same 'wavering' tone as observed before is still apparent. The sound of records (played at 33 RPM) seems to be slightly slower, not fully getting up to speed - and there is no change / improvement to the consistent wavering sound. I'm going to try 45's to see if the pulsating wavering is similar or slowed by comparison. I could also record a video and post to youtube if that would be helpful (maybe for someone) to help me troubleshoot the issue...

    I should add that the console was kept by a single owner, indoors in a temperature-controlled environment until I acquired it. In other words: it's fairly clean (aside from the expected accumulation of dust) and has never been exposed to moisture.

    Does anyone have any other ideas?

    Any help would be greatly appreciated...
    Hale
     
  15. JFRACE

    JFRACE AK Subscriber Subscriber

    Messages:
    1,020
    Location:
    New Jersey
    just to double check, did you also do the motor? Something has to be bound up still. Sometimes it takes a few cleanings to get everything out. Are you using 90%+ isopropyl alcohol?
     
  16. Hale

    Hale New Member

    Messages:
    10
    Location:
    Kentucky
    Thanks for the reply

    I removed the 3 clips from pins that hold the motor, but did not free the motor from the rubber bushings that secure it to the baseplate. This still allowed access to clean / lube motor which turns drive spindle...

    Are you suggesting to remove motor and disassemble it to clean?

    I've been using De-oxit on electronic components
     

     

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  17. kydog

    kydog Super Member

    I’ve had good results on relubing my tables because they can lockup. The chassis should have a small balance pot on it to even out the speaker problem if there isn’t one on the main console.( The small black pot to the left of the Rt & Lt input cables) Should do the trick. Love my Magnavox console’s ( Had four at one time). I do have a spare table with a new stylus similar Too yours that works great if interested
     

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    Last edited: Feb 11, 2019

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