G9000 quick freshen of driver boards

Discussion in 'Exclusively Sansui' started by kevzep, May 2, 2018.

  1. kevzep

    kevzep Its all about the Music Subscriber

    So I got this G9000 about a month ago, and I gave it a quick check over and repair when I got it, I don't really have the time to do the full restore at the moment, so I thought I would just go over the driver boards and get those done...
    I used some FG, Muse, and Panasonic FC caps, and some KSA1220 and KSC2690 to replace those horrible Sony transistors.
    Also replaced the trimmers of course.

    This is an early 9000, so there are no fusible resistors in R17 and R20, interesting to note, they must have decided to put them in as a fail safe on later models.

    Those Sony transistors are fairly stressed which is why I replaced them, and weirdly, they put these plastic tubes over them, great to keep the heat in!!
    But they also applied that awful glue to them as well.

    If you have an older G9000 it would be worth checking your boards out, I had to take out some surrounding resistors to clean the glue off.

    So I put it back together and fired it up, set the bias and DC offset, now I am inspired to do the rest of it soon, I really like working on these big G receivers.

    Few Pics, you can see that glue crystallising and becoming corrosive.
    Glue in the plastic tube, glue on the transistor, glue on the surrounding components....hilarious!!
    IMG_6043.JPG IMG_6045.JPG IMG_6046.JPG IMG_6047.JPG
     
    Last edited: May 2, 2018
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  2. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    Good grief that's ridiculous, the glue there to hold the plastic tubes in place? and the tubes there because the leads on those transistors are very flimsy.
     
  3. kevzep

    kevzep Its all about the Music Subscriber

    Yeah, hilarious!!
    I never gave it a thought with my other G9000 which was in fact the later DB model, we've often talked about the differences between the two which I now know is more than just the DB designation.
    No fusible resistors.
    No T0126 transistors, they use these silly Sony things with the silly plastic tubes and corrosive glue, oh joy!!
    So there's a couple of things. I am sure when I work through this one that more things will show up...
     
  4. Robisme

    Robisme Sansui Enthusiast Subscriber

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  5. kevzep

    kevzep Its all about the Music Subscriber

    Oh oops, thanks Rob....I'll go back and correct that...

    Yes the legs on those Sony's are very flimsy which is why they put them there, and it is very close to the screw yep...
    Not a problem for the TO126 package though, they are thinner and have stronger legs, Sansui never used the plastic tubes in the later models which had the TO126 transistors in those positions.
     
  6. petehall347

    petehall347 the brandy coffee man Subscriber

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    looks to me someone messed up in board design and got the hole spacing mixed up .. those transistors would of bolted onto heat-sink otherwise .
     

     

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  7. kevzep

    kevzep Its all about the Music Subscriber

    I don't think so, that heat sink is there for the TO220 drivers which are on the other side, BUT those Sonys almost get hot enough to warrant a heatsink.
    The STV3 diodes are on the heatsink there for thermal tracking which doesn't leave a lot of room for anything else.
    However I was thinking that they really did cram those components on the board, they could have made it a bit bigger, there is room in the chassis...
     
  8. kevzep

    kevzep Its all about the Music Subscriber

    I found enough time to go through and do the rest of this unit, its fully recapped now, has a new 3 core power cable including the earth connection.

    Replaced the suppressor cap with a modern X/Y safety cap

    All caps except the Ovals are done. The ovals are actually fine, ESR is impressive for age, and leakage is good.

    I replaced all 4 relays, when the right channel had its catastrophic meltdown, it must have damaged the contacts in the speaker A relay, man they were torched!!

    I aligned the tuner and I have to say, in terms of sensitivity, my Pioneer SX1010 edges out in front, but the Sansui tuner sounds more linear.
    I spent a lot of time cleaning this one out, there was a lot of oily dust in it, maybe it lived in a wood working shop for a while? Not sure, but at the price I got it for, I am certainly not complaining...
    Glued the diagram back on the top of the transformer...
    Cleaned again, and cleaned and cleaned....
    These amps don't really sound any different after a recap, as there are no caps in the audio signal path, unless you are using the tone controls of course, so yeah, she sounds great...
    I am very happy with the way it turned out...
    IMG_6182.JPG IMG_6183.JPG IMG_6184.JPG IMG_6187.JPG IMG_6188.JPG IMG_6190.JPG IMG_6192.JPG
     
  9. Willy6

    Willy6 AK Subscriber Subscriber

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    Are all 4 relays the same?
     
  10. kevzep

    kevzep Its all about the Music Subscriber

    No, the protection is an MY4-0-24, the two speaker relays are LY2-0-24 and the soft start is a LY2 as well, but I used the plug-in type for the soft start which has the bigger spade type terminals on it, easier to solder to, also used the casing from the original relay because it has the ears on it to screw into the chassis, the new ones do not have that option..
     
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  11. Willy6

    Willy6 AK Subscriber Subscriber

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    Thank you for the part numbers I'll be putting an order in for all 4 of those soon.
     
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  12. Overundr1

    Overundr1 AK Subscriber Subscriber

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    Did you notice the two voltage dropping resistors on the power supply running hot? Seems to me I upped the wattage on them and had an immediate lowering of temp off the power supply. If needed I will go dig through old threads and find where I brought this up a few years back.

    Of course I then had to go find the thread lol---

    http://www.audiokarma.org/forums/index.php?threads/g9000-notes.737856/

    -Lee
     
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  13. kevzep

    kevzep Its all about the Music Subscriber

    Yes they do get a bit toasty don't they, I might go back and slip some uprated resistors in there......good call!!
     
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  14. petehall347

    petehall347 the brandy coffee man Subscriber

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    i know its a long way round plus i know nothing but could the AF supply transistors etc be beefed up a bit then lowering the resistance of the dropper resistors to keep them cooler ..
    makes me wonder why they used higher voltage and dropped it so much .must be for more current .
    my main thought was it might gain more available power plus supply might run cooler .
    p.s i made that up for fun .:D .
    sorry been drinking again .
     
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  15. kevzep

    kevzep Its all about the Music Subscriber

    Yeah this is one of the many reasons I do not drink alcohol, talking absolute crap....Hahahha, all good though Pete...
     
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