Kenwood KR-9400 Multiple Issues; Help Wanted

Discussion in 'Kenwood-Trio/Kensonic-Accuphase' started by Shaun b, Apr 15, 2018.

  1. Shaun b

    Shaun b Member

    Messages:
    51
    A while back I posted this problem but life happened and I had to focus on something else for a minute but this weekend I decided to look at this thing again. I will tell you what I know and then I hope someone can/will help me get this beast going, so here we go.....
    When I first got this thing it would power on but no sound from any source including headphones. I found the service bulletin with the service manual and I followed it to the letter and then turned on again. No sound still, anywhere.
    so by process of elimination, I have found the problem to be in the left side output board. If I "un-seat" it from the main power board and have only the right side hooked up, it comes out of protection within a couple seconds of powering on. However I soon discovered another problem, I still get zero sound from any source.
    Heres a couple other things I know or have done that may or may not be a clue to someone as to what is going on.

    1. when I powered it on the first time, all lights including the small red lights for each source were working as well as both meters were working. all 4 fuses have been tested, replaced and tested again. they are good however I'm not getting but have my source lights and both meters have stopped working.

    2.output transistors have matching output voltages of -68 and +68

    I'm not a technician but I have a general understanding of components and their function. I have several meters and I can solder pretty good and I'm not afraid to get inside this thing as long as I have instructions. I'm pretty sure I can figure out what is going on in the output board but I'm not sure why I'm still not getting sound from the other side when it does come out of protection. Any help would be greatly appreciated. Even if it someone all the way in Honduras ;) Also if it gets to the point where I feel I cant get this thing fixed, I would not be to proud to send this to a trusted and well known member of this site who has repaired gear for other members. If anyone has used someone from this site with positive results, I would love to hear about them also. Thanks in advance for any help.

    Shaun

    PS I have cleaned the pots and both pins are in the right way on the back.
     

     

    Please register to disable this ad.

  2. gort69

    gort69 AK Subscriber Subscriber

    Messages:
    950
    Location:
    Vancouver, WA
    I remember....if you're certain the jumpers are in correctly (on the horizontal, not the vertical) , I'd check the regulated voltages on the power supply - +14VDC at pin 57 and -14VDC at pin 60 and for +55VDC/-55VDC at the big caps
     
    Last edited: Apr 15, 2018
  3. rickl

    rickl New Member

    Messages:
    41
    Location:
    Twin Cities
    Shaun, my KR-9400 Service manual says the collector of Q201/Q203 should be +55vcd and -55vdc for Q202/Q204. I'd suggest you measure the voltages listed in the service manual and post your findings with what is listed.

    I'd focus on the power supply , pre amp , main amp boards first. As gort listed above, +/-14vdc and +/-55vdc are used throughout.

    Example, pin1 on the preamp (x08-1270-00) should be -14vdc, pin2 should be +14vdc. Gort's request to measure pins 57/58 and 60/61 on the power supply board (x00-1640-10) will tell a few things. You can use pin 59 for the ground clip on your DVM.

    I haven't been in my 9400 lately so I don't remember how hard this is to measure. use common sense and use the service manual for guidance.
     
  4. mbz

    mbz AK Subscriber Subscriber

    Messages:
    1,651
    Location:
    Melbourne, Victoria
    Not familiar with the amp/Rx.
    Does the unit have a mains voltage selector on the back?
    Or does the voltage printed on the back plate match the mains voltage?

    Is it a 100Vac unit running on 120Vac mains?
    OK, it's a long shot...
     
  5. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
    25,039
    Location:
    uk.. the middle bit
    main left amp board voltages at pins 7 10 and 16 ? obviously needs board installed
     
  6. Shaun b

    Shaun b Member

    Messages:
    51
    Thanks for all the help you guys. Here is what I got so far and Im not sure exactly what it all means but here goes;

    All 8 OT are + and - 62VDC
    Preamp pin 1 -14.6
    2 0

    power supply pin 57 -0.8
    58 -0.7
    59 0
    60 -14.8
    61 -14.8

    main left pin 7 59.2
    10 62
    16 59
    I hope its not terrible but it doesnt seem good.
     
  7. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
    25,039
    Location:
    uk.. the middle bit
    no fuses blowing so check all resistors .especially any fuse ones
     
  8. gort69

    gort69 AK Subscriber Subscriber

    Messages:
    950
    Location:
    Vancouver, WA
    I would pull and test Qk1 (2sc1419) - I suspect it's fubar. (which isn't surprising)
     
    rickl likes this.
  9. Shaun b

    Shaun b Member

    Messages:
    51
    Im on my way home from work now and will check that I will let you know what I find. Thanks for the help, its very appreciated
     

     

    Please register to disable this ad.

  10. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
    25,039
    Location:
    uk.. the middle bit
    i missed those supply voltages ..
    check fk4 first .
     
  11. Shaun b

    Shaun b Member

    Messages:
    51
    Fk4 is good as is all fuses.

    Well if 2SC1419 wasnt my problem before, it certainly is now. It came apart rather easy and in such away that I could see inside the plastic. Im not sure what its supposed to look like but it appeared "burnt up" inside. I have already ordered a new one so now I wait. Is there anything else you think I should look at or wait until the new part is in? Thanks again.

    Shaun
     
  12. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
    25,039
    Location:
    uk.. the middle bit
    check the other power supply components
     
  13. Shaun b

    Shaun b Member

    Messages:
    51
    so my part came in and i installed it last night. Now for the first time, all the lights and dials came on and it is beautiful, but still no sound. It still will not come out of protection mode. I took my readings again after replacing 2SC1419 and here they are;

    all 8 output transistors are -62 and +62

    pin 57 13.5
    pin 58 13.5
    pin 59 0
    pin 60 14.6
    pin 61 14.6

    preamp pin 1 -14.6
    preamp pin 2 0

    im going to start again this morning looking for the problem but again, I would take any advice or suggestions from those who have any input.

    Thanks to all who have chimed in.
     
  14. gort69

    gort69 AK Subscriber Subscriber

    Messages:
    950
    Location:
    Vancouver, WA
    As you said - multiple issues.

    Re: 0V at preamp pin 2. Set your tape monitor switch to source and set the input selector to phono and recheck.

    Check pin 5 on the tone board (+14VDC) and pin 6 (-14VDC)

    How is your meter connected to get +/- 62VDC at the outputs? (black to chassis, red to transistor case) That's what has me puzzled - should be +/-55VDC. A volt or two either way, but 7 volts is off by quite a bit.
    Measure voltage at the filter caps - black lead to chassis and red to each of the 4 lugs. 2 of them should read 0V, and the other two +55VDC and -55VDC give or take.
     
  15. mbz

    mbz AK Subscriber Subscriber

    Messages:
    1,651
    Location:
    Melbourne, Victoria
    Regarding +/-B at +/-62Vdc.
    This is an unregulated supply.
    What is the voltage rating on the main filters. SM has 15000uf/50V with a +/-B at +/-46Vdc.
    If main filters are 50V then it's a voltage "input/selector" problem
    If mains are 63 or ...80V then it's a SM error, move on...
     

Share This Page