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TRC-931 no sound

Discussion in 'Tech talk' started by Vintage Guy, Jan 10, 2017.

  1. Vintage Guy

    Vintage Guy New Member

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    Hello everyone. I was a member on the old site and now I have an issue with my Lasonic TRC-931.

    I lost all sound for it. The speakers pop like normal when turned on and buzz while on, but I get no sound, none from the tape deck either.

    I thought it was the tuner board and replaced all the CAPS on it and also looked for cracked solder joints but that did not work. I next removed the main board and checked for cracked solder joints and found a couple questionable but that was it.

    Anyone have any ideas?

    I lost this one and my parts Lasonic 931 in a days span! Soo bummed!

    IMG_20170109_170704113.jpg IMG_20170109_171133645.jpg
     
  2. Vintage Guy

    Vintage Guy New Member

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    Anyone??
     
  3. T-ster

    T-ster Moderator Staff Member S2G Supporter

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    I have a similar problem with my MX-920 mate, have recapped it, check for dry joints, all sorts and i just cannot solve the no sound issue.
     
  4. Vintage Guy

    Vintage Guy New Member

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    Thanks for the replay T-ster. Sorry you are having the same issue.

    When I but my cases back together and powered it up I noticed when I placed my hand near the volume and balance controls the static noise increased. Therefore I'm going to take it apart and check those controls, got nothing to loose! And it lost sound while the radio was on.
    I was just about done with this restoration too and this happened! Sucks!

    I'll post back what I find if anything.
     
    Brutus442 likes this.
  5. Brutus442

    Brutus442 Well-Known Member

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    tape/radio selector switch maybe? Volume pot? Not sure about this unit....
     
  6. T-ster

    T-ster Moderator Staff Member S2G Supporter

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    Yup same for me VG, i put some hours diagnostics in whenever i have time which hasn't been sucessful yet but i'll keep trying.

    I think im going to get a new power supply ofr mine or at least replace the resistors on the board, i read something recently about a box pwering up with no sound and thats what it was. Gonna try everything i can find.
     
  7. Vintage Guy

    Vintage Guy New Member

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    Just removed the volume eq board and found some oil like goo on the balance pot. Otherwise everything "looks" fine.
    I then cleaned the pots with tuner cleaner and since it's out, I'll replace the 10 caps on that board.
    Hope that fixes it!
    In theory could the oil like goo have shorted the pot? I suppose so...
     
  8. Vintage Guy

    Vintage Guy New Member

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    No power supply to help with no sound?
    It must not be the AC transformer ps right because the box is powering up.
     
  9. T-ster

    T-ster Moderator Staff Member S2G Supporter

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    Let us know how the cap change goes, I'm thinking i may have to do the same and recap everything i can find.

    I read of one guy having a box with no sound yet powering up and it turned out to be low voltage from the AC not supplying enough juice for the amps to output properly. Long shot but may be worth a look.
     
  10. Vintage Guy

    Vintage Guy New Member

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    Got the new CAPs all soldered in last night but did not power it up yet. I have to finish putting it back together and won't able to do that until Sunday night most likely.

    Stay tuned!
     
  11. T-ster

    T-ster Moderator Staff Member S2G Supporter

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    Aha i was awaiting an update, i'll cross my fingers for you man :thumbup:
     
  12. Vintage Guy

    Vintage Guy New Member

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    T-ster buddy!

    She's fixed and rockin now! Sweet! Another one saved from the crusher or parted out!
     
  13. T-ster

    T-ster Moderator Staff Member S2G Supporter

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    Mate that's amazing!

    Damn that must feel so good. So it was recapping the volume balance board that did it? We're they all the same caps or lots of different ones?

    Anyway what a result :yahoo
     
  14. Vintage Guy

    Vintage Guy New Member

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    Yeah, not sure if it was from me cleaning the volume and balance pots or the replacement of the CAPs.

    I would have liked to do one thing, power it up and if that did not work, do the next but I had to remove two boards just to get to the vol/bal/eq pot board therefore I did those caps while cleaning the pots.

    There were 10 CAPs of three different types on the board. I get all my CAPs at Mouser. I also did the large CAP at the power supply. The only CAPs I did not change out are the ones on the large board, there's a lot of them on that board.

    It was up and blasting last night, so happy now!
     
    Last edited: Feb 3, 2017
  15. T-ster

    T-ster Moderator Staff Member S2G Supporter

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    Ah thats great news man. Well thats it then, i am going to order caps for the whole board and go ahead and recap mine plus the power board, fingers crossed!
     

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