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Scrap my STR7055A?

Discussion in 'Solid State' started by beedub, Dec 29, 2017.

  1. beedub

    beedub Active Member

    Messages:
    134
    Location:
    Kingston, Ontario
    I recently got given a STR 7055a in cosmetically good shape.
    It has good sound on the right but very weak (controllable by the volume knob) sound on the left channel.
    Cleaned, deoxidised, the balance when turned is still only a weak sound on the left side.
    no obviously bad controls.
    Going through the control knobs right to left I found:

    function: ok
    stereo: not ok- L, R, reverse: no effect, same , good sound on right side only.
    filter: ok
    treble: right full effect, left little or none (weak sound, hard to tell)
    bass: same
    speaker A/B/C all weak on left.
    suggestions? I do not see anything obvious like trace cracks, bad joints, etc.
    if i put it all the way to left, it has weak controlled volume.
    Any suggestions before i save the knobs?????

    Edit:
    I'd like to fix it if possible, anyone got any suggestions?
     
    Last edited: Dec 29, 2017

     

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  2. redk9258

    redk9258 Super Member

    Messages:
    1,533
    Location:
    Illinois, close to St. Louis.
    Why on Earth would you scrap it? Give / sell it to someone who will appreciate it. I'm sure it is worth repairing.
     
    UncleBingo likes this.
  3. UncleBingo

    UncleBingo AK Subscriber Subscriber

    Messages:
    990
    Worth fixing imo. Hurry up and donate it for a write off! (Do you have that option for charitable donations up there ?)
     
  4. beedub

    beedub Active Member

    Messages:
    134
    Location:
    Kingston, Ontario
    I think"worth fixing, repairing" is only worth it if you know what needs done and it is affordable.
    I'd really like to fix it if possible, anyone got any suggestions?
     
  5. 62vauxhall

    62vauxhall AK Subscriber Subscriber

    Messages:
    1,820
    Plug in some headphones. See if both channels are equal through those.
     
  6. Dazaa

    Dazaa Super Member

    Messages:
    1,072
    Location:
    London England
    I think these have a switch on the back to change between pre out/main in and coupled, give it a good clean as its easy to miss. I had a similar era sony with exactly the problem you describe and assumed a dead channel till I cleaned the switch
     

     

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  7. beedub

    beedub Active Member

    Messages:
    134
    Location:
    Kingston, Ontario
    It Lives! thanks to some incredibly patient help from another audio enthusiast. i had to dig out my 40 year past electronics skills, it only hurt a little.
    thank you so much! It had two likely things in the preamp section - two caps that may have been weak, and maybe the solder pin joints on the board.
    caps replaced and many pins touched up with fresh solder.
     
  8. redk9258

    redk9258 Super Member

    Messages:
    1,533
    Location:
    Illinois, close to St. Louis.
    See. Much better than landfill. Oh, the horror!
     
  9. UncleBingo

    UncleBingo AK Subscriber Subscriber

    Messages:
    990
    Woohoo! Nice work.
     

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