I need an Eleven GX expert.

Discussion in 'Kenwood-Trio/Kensonic-Accuphase' started by quaddriver, May 2, 2018.

  1. quaddriver

    quaddriver 120 What's per channel Subscriber

    working on of these that appears to be a virgin, its not blown up, just some scratchy controls, seriously bad solder joints on the 'MAC' (aka tone) board and burnt lights. so ok, easy fixes but it runs warm, too warm left side so I go to set bias. I cannot find any settings for the 11GX, eleven 1, 2, 3 and G but not GX and what I do find between here and diyaudio varies to the point where it appears to be rumor.

    The G book says 22 mv across the test pins on either channel which are the extreme ends of the emitter resistors. fine.

    VR1 and 2 are self explanatory.

    if I crank the pots to the least I get high 70's left and mid 40's right.

    there was a post somewhere that said the GX is a base exchange model of the G. no. while much of it is similar, there are acute differences on the amp board. I am able to track and correspond the topology but the ASO for the GX is utterly different from the G and there seems to be some value differences.

    Lettuce consider the left channel, which is too high and too hot. The G SM and SCM are on hifi-E. page 23, blow up to 250%

    the bias is set via VR1 which is in parallel with Re21 and flows current between Qe5 and Qe7

    The G spec is 22mv with Re21 at 47ohms and VeR1 at 100 ohms.

    All the silicon is the same but in the same positions in the Gx I find Re21 is 100 ohms and VeR1 is 200 ohms.

    at best, setting for setting the GX will flow half the current and it seems have twice the bias current otherwise.

    Does anyone have a GX or a GX SCM and are these parts values correct and/or is the setting 22mv or 45 which appears to be reachable. now I need to look tomorrow to see if the bias resistor for the drivers are the same, G vs GX as that could confuse things.

    now why the left channel is higher is simple - VeR1 is actually 250 ohms instead of the 200 found on the other side. I figure the bias difference is proportional to the error in the larger pot.

    the thermals are STV-4s and sure enough, let it stew to where the steel portion of the frame gets warm and the diodes are flowing and it does lower to low 70's, but still way too high (beyond me why these are mounted to the steel frame NEXT to the heatsink when ON the heatsink would be more direct.)

    At any rate, this is an expensive disaster looking for a place to happen. I have 100 ohm half watt resistors all over the place but 200ohm pots are going to require an order, unless we find that other values need to be used....

    any ideas?


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  2. quaddriver

    quaddriver 120 What's per channel Subscriber

  3. gort69

    gort69 AK Subscriber Subscriber

    Vancouver, WA
  4. quaddriver

    quaddriver 120 What's per channel Subscriber

    I think it does, so if I fix the bad 200 ohm pot so it is back in range, I can get her near the 45ma. its a scary number for a pioneer guy, but who am I to question kenwood. thanks!
  5. oldboats

    oldboats AK Subscriber Subscriber

    Fargo, North Dakota
    If you feel too concerned about it, I am sure that someone would be willing to trade you a Pioneer or three for it. (Hint, hint...)
  6. kenwoodm2a

    kenwoodm2a Member

    I have a GX as well that I refurbished a couple years ago. Recapped, replaced all bulbs with Led's. Of all my Kenwood components, I keep being drawn to this unit for it's warm and pleasant sound quality more than the others.
    I have the same issue as you with the bias setting with one channel being more that the other and unable to bring it down less than 70. I am currently in the proces of doing some FM Tuner alignments with some of my other units but when I get to this one, I will revisit the bias and start to trace the troubled area. The only service manual I have is the same as yours for the Eleven G but I do have the GX power board schematic and parts list that is a supplement to the G model. The only difference between both units is the power board.
    So I was also doing the bias adjustment based on what the G service manual started as being 22 mv but it would appear that from the literature above, the GX is 50 mv.
    Guess I need to spend some time on this unit.


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  7. Gertjan90

    Gertjan90 Member

    Wait until you do a Philips 594 or 794, 75mA recommended in SM.. Have never seen one with all original outputs.

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