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G-7000 for reconditioning

Discussion in 'Exclusively Sansui' started by Hyperion, Sep 24, 2018.

  1. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    So, I finally have one of these G-7000 beauties on my bench for a refresh, it is working, but is very very tired and needs a good going over. It belongs to another AK member, and he said he wants me to 'do what I would do to it, if it were mine'. :) Well, I think hardly anyone can pay me enough to do as much as that. :D

    However I will give this unit my usual level of care and attention, when it's finished I promised him it will be the best sounding G-7000 north of Watford Gap. :D

    Here is the driver board - minus the 4 big local filtering capacitors, glue not too bad, but as usual it has taken its toll of components on this board.
    IMG_2441ar.jpg

    More later, and as the restore progresses. :)
     
    Last edited: Sep 24, 2018
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  2. Leestereo

    Leestereo Super Member

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    Looking forward to updates on this project.
     
  3. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    You will notice some very familiar component selection techniques and choices used during this restore, your excellently documented restores have been a considerable influence on me. ;)
     
    Last edited: Sep 24, 2018
  4. ManyMoonsAudio

    ManyMoonsAudio AKA paul79 Sponsor Subscriber

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    REALLY great receiver here. This one and the G-7500 are real sleepers in this lineup. Great phono sections in all the G series receivers as well.
     
  5. kevzep

    kevzep Its all about the Music

    On the phono board I think it is, there are some VD1212 and also the voltage dropping resistors are always out of spec too.....

    I've worked on two of them and they both had this problem with the resistors...

    They are great units though, a taste and a very nice taste of the TOTL models...
     
  6. KingBubba

    KingBubba "Too Much Stuff" Subscriber

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    I have always been under the impression from posts here on AK that the G-7500 was a touch on the inferior side from other receivers in the G line. I have one that needs repair, but I have held it off due to that impression I have gotten about its inferiority.
     

     

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  7. kevzep

    kevzep Its all about the Music

    The G7500 has the same power-amp as the GX700 series, when they have serious issues with the power-amp, they can be difficult to fix.
    It does not necessarily mean they are inferior...
     
  8. ghazzer

    ghazzer Senior Member Subscriber

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    Here is a chart I just made showing the boards used in three G- series receivers. I took this from the schematics and cannot guarantee that I didn't miss anything. It seems to indicate that the guts of the G-7000 and G-7500 are the same, except for the F-2980 bd and the supporting power supplies. The components on the boards may be different.

    It is interesting to note that most of the board numbers in the G-7000 and G-7500 are sequential, indicating to me that they have the same basic design. The G-7500 is almost the G-7000 stepped up to the F-2980 power Amp used in the G-X700 series.
    G-7000: 82WPC, rails = ±52vdc
    G-7500: 90WPC, rails = ±63vdc
    G-6700: 90WPC, rails = ±61vdc


    PWAs G series.jpg
     
    Last edited: Sep 26, 2018
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  9. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    Here are the before & after pictures for the G-7000 driver board.

    Before.
    IMG_2441ar.jpg

    After.
    IMG_2445a.jpg

    Not tested yet, I'll make sure it's working & set up before I proceed to the next major board. I am going to concentrate on the front panel mounted boards for a while, as they are all quite small and will get that part of the restore out of the way before I get to the larger more complex chassis mounted boards. ;)
     
    Last edited: Sep 30, 2018
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  10. sansui88

    sansui88 I'm a Bass Line Junkie

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    Looking good John, piece of the puzzle done
     
  11. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    Thanks Mike, Amazing to think that I actually changed 38 components on the driver board. (and there are 2 more components to be done as, due to a miscount I ran out of parts).

    I have now done the Mic Amp Board F-2857 (very small) and am now turning my attention to the Tone Amp Board F-2855,

    Which looks like this:
    IMG_2447a.jpg

    Room for improvement there I think ;)
     
    Last edited: Sep 30, 2018

     

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  12. sansui88

    sansui88 I'm a Bass Line Junkie

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    I see 11 caps to replace. I hope its goes a breeze for you
     
  13. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    There are actually 12 obvious candidates, but there will be a few more getting changed, and there will be 2 electrolytic capacitors less when I've finished. ;)
     
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  14. kevzep

    kevzep Its all about the Music

    John, the F2852 board is the one I was talking about, it has a couple of MV12 diodes, and 4 resistors which need changing along with the usual caps etc.
    R45,46,47,48. They are 100Ω, I'd hedge a bet that they have drifted a lot. This is a real problem area on this amp.
     
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  15. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    Thanks Kev, I am aware of that board, it's going to receive some special attention, and your tips have been duly noted. :thumbsup:

    Update:
    I've just been and measured those resistors, and one of them is 10% high, just the look of them would have rung alarm bells for me. :D
     
  16. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    Here are the before & after pictures for the G-7000 F-2855 Tone Amp board.

    Before.
    IMG_2447a.jpg

    After.
    IMG_2463a.jpg

    Note: Two pairs of back-to-back orange capacitors replaced with a single quality bipolar (green) with the second capacitor position linked, Two bead diodes have each been replaced with 2 x 1N4148, 20 components replaced in all.
     
    Last edited: Oct 4, 2018
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  17. Overundr1

    Overundr1 AK Subscriber Subscriber

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    Looking good sir, like the judicious use of those WIMA films and Muse bi-polars.
     
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  18. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    I plugged everything back in this evening, checked the work done so far, and dialled in the driver board before I continue with the rest - all good. :thumbsup:
     
  19. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    Wheeee... - the EQ is out - the 'famous' F-2852. ;)

    IMG_2469a.jpg

    I have already removed the switch (S01 - the input selector switch) - which has now had a proper clean, and will be refitted in due course. And I also removed C26 which turns out to be bipolar! (& C25) - I missed that - annoying. :oops: :)
     
    Last edited: Oct 8, 2018
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  20. Overundr1

    Overundr1 AK Subscriber Subscriber

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    One of the fabulous 'fiddly' boards that require bench time not in proportion to its size :)
     
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