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Car speakers work on AM but only right side work on FM

Discussion in 'Audio' started by Indetrucks, Apr 7, 2018.

  1. Indetrucks

    Indetrucks

    5
    1
    Apr 7, 2018
    (sorry if in the wrong sub-forum, mods please move if needed)

    Hi all,
    New here but not new to forums. I was going to post this on one of my Toyota forums, but I think this may be specific to internal radio issues.

    My 1987 4Runnner has a stock Technics tape deck in it. In AM, it sounds great but in FM, only the right side speakers work. I can faintly hear sound from the left speakers if I crank the volume knob to max (adjusting balance to left side only).

    I've played with the fade button but it's both left speakers regardless of front or back that are hard to hear. Occasionally when adjusting the volume the left speakers will kick on for a split second, then turn off and nothing more.

    Is there somewhere I can send the radio for a repair/cleaning? I want to maintain the stock look and feel, so replacing the unit is not an option and I have had no luck on eBay for a used replacement.

    I'm handy with soldering and tinkering, so not afraid to open it up. I just have no internal radio experience.

    Any advice?
     
    Last edited: Apr 7, 2018
  2. Indetrucks

    Indetrucks

    5
    1
    Apr 7, 2018
    IMG_20180319_134220595.jpg
     
  3. davenn

    davenn Moderator

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    Sep 5, 2009
    so does the tape deck sound OK both channels ?

    If yes, then the problem lies in the FM stereo decoder area of the circuit
     
  4. Indetrucks

    Indetrucks

    5
    1
    Apr 7, 2018
    Sadly don't have a tape deck to try. I will ask my mother in law if she has one.

    Is that a fairly difficuly diagnosis/repair?
     
  5. davenn

    davenn Moderator

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    Sep 5, 2009
    you mean you don't have a cassette tape lying around ?

    without service info ... yes
     
  6. KJ6EAD

    KJ6EAD

    1,114
    157
    Aug 13, 2011
    You may just have a bad volume potentiometer (the component behind the knob).
     
  7. davenn

    davenn Moderator

    13,264
    1,749
    Sep 5, 2009

    maybe, but I doubt it since both channels are OK on AM
    The Mono AM signal will be split to feed both channels
     
  8. KJ6EAD

    KJ6EAD

    1,114
    157
    Aug 13, 2011
    Of course, but where in the chain does the AM audio signal get distributed? If it's after the, presumably dual, volume-pot-controlled preamp, that would explain the intermittency experienced while adjusting the volume pot in FM.
     
    Last edited: Apr 10, 2018
  9. davenn

    davenn Moderator

    13,264
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    Sep 5, 2009
    It would have to be BEFORE the volume pot, else you wouldn't be able to control the AM audio level, aye ;) ;)
     
  10. Indetrucks

    Indetrucks

    5
    1
    Apr 7, 2018
    Sorry, still looking for a cassette tape. Yes, I actually grew up with them...just don't have one.

    But I do appreciate the help!
     
    davenn likes this.
  11. Indetrucks

    Indetrucks

    5
    1
    Apr 7, 2018
    Bummer, I was afraid of that.
    I have contacted 4 local specialists via email with no response. Does anyone here recommend a specialist online I can send the head unit to?
     
    Last edited by a moderator: Apr 26, 2018
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