Sansui G5700, No sound, need tech info about possible unusal solution

Discussion in 'Exclusively Sansui' started by FE3T, Apr 14, 2017.

  1. FE3T

    FE3T Member

    Messages:
    55
    I was stupid enough too let someone borrow my G5700 for a while, and got it back silent.
    I suspect that it was hooked up too more than one pair of speakers, and driven hard enough too blow the output stage. Since then it has been stored for some years.

    I don't think I am able to fix this my self, and suspect after reading some posts about these receivers that not even the local tech would be able to fix it without spending a lot of time (and money) on the job, Resulting in a final bill well above what the thing are worth.

    A non original working unit are in my opinion better than a original non working unit, as in the last case its either too can it or try to sell it as is. (which probably would be almost the same as giving away.

    So my question to those who have experience with these are:

    Would it be possible to remove the power amp section and use the receiver as a Tuner/pre without loosing any of the functions? eventually replace the whole power amp section with a Hypex UCD/SMPS combo?
     
  2. moefuzz

    moefuzz Active Member

    Messages:
    343
    Location:
    Peeyong Bangyou
    .

    You are talking sacrilegious crazy things here on Sansui forum.


    .
     
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  3. Hyperion

    Hyperion Roobarb & Custard Subscriber

    Messages:
    39,518
    Location:
    Hertfordshire, UK
    What you suggest sounds like just as much effort as having it repaired properly - why don't you take it to a tech for an estimate, before re-inventing the wheel. :confused:

    I hope that 'someone' has offered to pay for the repairs. :idea:
     
  4. redrooster

    redrooster who was that masked man?

    Messages:
    1,263
    Location:
    geraldton western australia
    I havent worked on that model but I cant imagine that it would be that hard to replace the outputs. It just depends on how much experience you have at fixing things I suppose. There maybe an AK member in your area that could take a look at it? Where ever that is?
     
  5. ghazzer

    ghazzer Sansui addict Subscriber

    Messages:
    2,666
    Location:
    Sykesville, MD
    Do you have the manual and schematics? You can register here (free) and then DL the manual fro the G-5700/6700/7700.

    https://www.hifiengine.com/manual-library.shtml

    All three share the F-2980 main board, with the P/S, the main amp and the drivers that feed the output transistors. IMHO it would be better to get a working receiver that to try to convert your G-5700 to a tuner.

    The four output transistors are located on the F-2981(L) & F-3093(R) boards and mounted to the large black heat sink. If you unplug the G-5700 and remove the bottom cover you can see the track side of the F-2980. The two rows of jumpers across the bottom of this G-6700 pic lead over to the OP TRs and emitter resistors. Using the schematic you can test continuity/resistance across the TRs and look for any shorted junctions. Opened junctions take a little more effort.

    The F-2980 of the G-5700 may not be as fully populated as the G-6700, and some components will have different part numbers or values.

    EDIT(8/12/17): F-Bucket has deleted links to photos hosted there, so I have uploaded the "X-Ray" pics of the F-2980 board to another thread. I will keep updates loaded there and just reference later posts to that location.

    http://www.audiokarma.org/forums/in...ver-restoration-attempt-g-6700.480777/page-18
     
    Last edited: Aug 12, 2017
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  6. LBPete

    LBPete Rolling Along Subscriber

    Messages:
    10,771
    Location:
    Long Beach, CA
    Make sure the tape monitor is in the correct position. Work all the switches to see if there is any change. Do you hear a click a few seconds after you turn it on? Where are you located?

    - Pete
     
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  7. jd2005

    jd2005 New Member

    Messages:
    20
    just repaired a sansui g5700 which i have received as a dead unit. same problem. tuner works but no sound.

    I have assumed that at least one of the channels output transistors are burned out.

    Why both channels are silent ? that is because of the protection circuit. if it identifies that one channel at least is not good then it will not trigger the relay. so first thing to do will be to look for the relay and see if it triggers or not. if it's not then it is probably one of the channels or both.

    Next it requires an electronics qualified tech to troubleshoot the circuit. In my case there was a total burnout of a power transistor and accompanying parts such as the 0.33 resistor, the 220Om resistor and even the bias trimmer resistor (which i think started the whole problem).
    ).

    I am only a hobbyist (but qualified electronics person…) , but i can tell you that it was not difficult tracking the problem and fixing it. So... no... I don't think that you should make such a decent receiver a tuner... :) . You can repair it and enjoy it. I myself was quite surprised with its sound quality.
     

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