HELP ..Me I made a mistake Blew-Up my TECHNICS SA 600 Receiver & Need a competent Tech in Michigan!

Discussion in 'Solid State' started by Harvestor, Jun 13, 2018.

  1. Harvestor

    Harvestor Well-Known Member

    Messages:
    810
    Location:
    Land of 1776
    Hello there Audiokarma members...
    I'm so pissed at myself!...i know better...


    After I made 5 attempts to get the idle current to stabilize a 8mv .... which I was successful everytime.. but after several days I'd notice the left Channel was weaker with the bass...so I'd check and sure enough the voltage was lower than the other channel.. had to readjust..
    But yesterday's attempt was a big mistake!
    I shorted out the transistor and watched a couple of tiny transistors glow before I could shut down...
    So...
    I need to have a Professional that comes Highly Regarded & Recommended by Audiokarma members!... preferably in MICHIGAN.... so I can drive to Drop the Receiver off....
    This Receiver means a lot to me! & Was like brand new before I had to try to adjust the idle current or Bias...
    HiFi Engine has the free service manual

    https://www.hifiengine.com/manual_library/technics/sa-600.shtml

    Anyway any help would be greatly appreciated i'd hate to have to sell it for parts or give up on it..... this Receiver means more to me than I can say, so much so that I am going to be selling one of my favorite long rifles to pay for it's repair "if it can be done".
     

     

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  2. Watthour

    Watthour Electron Rancher - JS3600

    Of course, it is repairable. There are several reputable people in Michigan. Hopefully a "volunteer" will chime in.
     
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  3. c.coyle

    c.coyle From the Fabulous Downtown Lounge Subscriber

    Messages:
    2,973
    Location:
    40.3329535 -76.4231855
    As they say, "real radios glow in the dark." o_O

    Seriously, many here have done something like that, if not worse. There are two kinds of electronics geeks: Those who have melted/exploded/burnt something, and those who are going to. It's definitely fixable.
     
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  4. ickyfrog

    ickyfrog AK Subscriber Subscriber

    Messages:
    68
    Location:
    Exton, PA
    Very sorry to hear this and hope you are able to get it repaired quickly. Just for the benefit of a newbie, exactly how did you short the transistor? Were you using a screwdriver to adjust a trimmer pot and it touched the transistor lead ? Or maybe using a multimeter probe? Just trying to add to my knowledge here.
     
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  5. Harvestor

    Harvestor Well-Known Member

    Messages:
    810
    Location:
    Land of 1776
    The probe from the fluke test meter at the test point best I can tell weakend the leg of the white transistor above the power transistor.. and broke & shorted...
    I was going to find a tech anyway to recap and replace anything needed... But now I am forced to get this fixed.... What this is taught me is when you have something this perfect that was never touched before me leave it alone... But all the talk of 40 year old equipment being out of spec and this adjustment being such a simple one... Got me to thinking to check the millivolts which it was 12 to 13 volts instead of 8 on each of the power transistor Idle current bias...
    If I get this thing fixed back to working I won't be touching nothing ever again LOL..
    I will stick to recapping speakers and refoaming speakers... I'll post a picture from one of the members here or the link to the adjustment and test point for illustration purposes..
     
  6. Harvestor

    Harvestor Well-Known Member

    Messages:
    810
    Location:
    Land of 1776

     

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  7. blhagstrom

    blhagstrom Mad Scientist, fixer. Subscriber

    Messages:
    12,653
    Location:
    Duvall, Washington
    Were you probing like that?

    Yes? You shorted an output transistor. That caused other parts of the amp to suffer high current (glow and burn).

    Vintage tech can fix it.
    Casper at Stereorehab in Chicago comes to mind.

    Luck finding anyone closer.

    Worst case, you need to ship it. Myself and others here on AK do repairs and recaps.
     
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  8. ickyfrog

    ickyfrog AK Subscriber Subscriber

    Messages:
    68
    Location:
    Exton, PA
    I learned to use minigrabbers not test probes when adjusting bias. And to connect the minigrabbers before powering on.
     
  9. Champco

    Champco Super Member

    Messages:
    1,406
    Location:
    Twin cities
    Be happy you did not blow a hole in your board. I have seen power transistors explode when isolated during troubleshooting. This was done by a Tech who primarily worked on digital. It was a small explosion but a large pop which destroyed the board. Shoulda seen the look on his face...
     
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  10. Harvestor

    Harvestor Well-Known Member

    Messages:
    810
    Location:
    Land of 1776
    I'll NEVER attempt to be doing a Technicians job like that again!
    Several hundred dollar mistake and I'll be selling off a coveted AK rifle to pay for it, this is a lesson for anybody else reading about my experience to consider the risk's... and I read others warning about something like this happening....
     
  11. OMGCat!

    OMGCat! AK Subscriber Subscriber

    Messages:
    2,678
    Location:
    Alhambra, CA
    I'm all about the mini grabbers for doing delicate work inside something that's powered on.

    Speaking of blowing up something by making a quick mistake, I once took out a channel on an amp I was working on while doing simple voltage measurements. Not in the normal way but I was trying to push a wire out of the way and I used the pen I had in my hand to do it. I didn't realize the shiny end was conductive but oh yes, it was conductive all right.

    OP don't beat yourself up about it too badly. The only way to learn is to do and in doing some stuff ends up going sideways. It would be better if it was gear that you didn't like but things don't always work out that way.
     
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  12. Champco

    Champco Super Member

    Messages:
    1,406
    Location:
    Twin cities
    Sorry for the monetary hit. Sounds like a expensive lesson. They have made millions of the AK's so you should have no trouble replacing it. Might you be making a little profit on it???? Hopefully you will have a greater Amp then before after being redone. Always a silver lining.
     
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  13. quaddriver

    quaddriver 120 What's per channel Subscriber

    we have rifles here too?
     
  14. rickl

    rickl Member

    Messages:
    59
    Location:
    Twin Cities
    while it might be too late for Harvestor, if you don't have mini grabbers you can add some heat shrink to the end of the probe so only the tip is exposed. Might help future projects.
     
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  15. toxcrusadr

    toxcrusadr AK Subscriber Subscriber

    Messages:
    31,100
    Location:
    Central Missouri
    I gotta get me some of those mini grabbers. They want a lot for them compared to regular probes and alligator clip probes, but just look at the money they can save you.
     
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  16. rudawg06

    rudawg06 New Member

    Messages:
    14
    I've dealt with Harry at:
    Seven Grand TV Repair
    fast pro service
    25642 W. 7 Mile Rd.
    Redford, MI 48240
    313-533-3635
     
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