Electron Kinetics Eagle 2C amplifier problem

Discussion in 'Technical Repair' started by MarioP2020, Sep 6, 2018.

  1. MarioP2020

    Thread Starter New Member

    Sep 6, 2018
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    Hello everyone! Noob here. Glad to have found this forum. I hope I can get some advice on repairing an older stereo amplifier I have.
    It's an Electron Kinetics Eagle 2C amp from the early 90's. It was assembled and inspected around mid December, 1992. One channel has gone out. I tried contacting the company through email, and also called, but have yet to get an answer! This has been a couple of weeks now. I have also tried searching for a schematic for this amp, but no luck!

    So, here is what I have done so far. I have checked the main power fuse, and the 2 fuses on the pcb, and they are all good. I then measured the voltage for all of the transistors. These are measurements I got from the top row starting from left to right. I have also included some photos. The first photo shows what appears to be some brown stuff on one of the caps. Not sure if it is from leakage or some kind of glue? The second photo show the channel A side of the amp, and the last photo shows channel B.

    (CHANNEL A) Starting from Top left (second photo)
    #1 Sanken 2SC2774 transistor B=.631 DCV/ C=48.0 DCV/ E=.018 DCV
    #2 Sanken C2168 transistor B=1.22 DCV/ C=47.7 DCV/ E=.627 DCV
    #3 Sanken 2SC2774 transistor B=.626 DCV/ C=48.0 DCV/ E=.017 DCV
    #4 Sanken A958 transistor B=46.4 DCV/ C=1.22 DCV/ E=47.3 DCV

    (CHANNEL B) Starting from Top left (third photo)
    #5 Sanken A958 transistor B=47.8 DCV/ C= -40.0 DCV and appeared to be dropping?/ E=46.1 DCV
    #6 Sanken 2SC2774 transistor B= -21.0 DCV and dropping in voltage/ C= 46.8 DCV/ E= -19.6 DCV
    #7 Sanken C2168 transistor B= -18.8 DCV/ C=46.8 DCV/ E= -18.9 DCV
    #8 Sanken 2SC2774 transistor B= -18.75 DCV/ C=46.9 DCV/ E= -19.4 DCV

    Here are the rest of the transistors located on the bottom. The measurements are:

    Channel (A) Starting at bottom left (second photo)
    #1(2SA1170) B= .603 DCV/ C= -46.55 DCV/ E= -.012 DCV
    #2(A958) B= -1.22 DCV/ C= -46.33 DCV/ E= -.600 DCV
    #3(2SA1170) B= -.593 DCV/ C= -47.3 DCV/ E= -.002 DCV
    #4(2SC2168 ???) B= -44.7 DCV/ C= -1.20 DCV/ E= -44.8 DCV

    (CHANNEL B) Starting from bottom left (third photo)
    #5(2SC2168???) B= -44.8 DCV/ C= -2.27 DCV/ E= -44.8 DCV
    #6(2SA1170) B= -1.15 DCV/ C= -45.9 DCV/ E= -.63 DCV
    #7(A958) B= -1.9 DCV/ C= -46.7 DCV/ E= -1.22 DCV
    #8(2SA1170) B= -1.42 DCV/ C= -46.1 DCV/ E= -.75 DCV

    I also measured the speaker outputs, and got these measurements with my Fluke DMM:
    Channel (A)= .001 DCV
    Channel (B)= -21.8 DCV and then starts to drop in voltage.

    The measurements for the OP-AMPS:

    OP-AMP (#1) Pin #1= -14.76 DCV/ Pin #2= -.025 DCV/ Pin #3= 15.27 DCV/ Pin #4= .002 DCV Perhaps there was no voltage on this pin #4?
    Pin #5= 14.80 DCV/ Both Pins #6 & #7 measured no voltage/ Pin #8= -14.76 DCV

    OP-AMP (#2) Pin #1= -14.73 DCV/ Pin #2= -.633 DCV/ Pin #3= -.677 DCV/ Pin #4= -14.8 DCV/ Pin #5= -11.50 DCV/ Pin #6= 15.28 DCV/ Pin #7= -.004 DCV/ Pin #8= -14.75 DCV

    Could someone help me figure out what may be causing one side not to work? Would be very grateful!


    Thanks in advanced!

    Mario P.
     
  2. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
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    Channel B is at fault, one transistor is not on, and from your voltage levels looks like it's shorted B/E,

    #5(2SC2168???) B= -44.8 DCV/ C= -2.27DCV/ E= -44.8 DCV

    This appears to be a classic push-pull output, also channel B has -21V dc at the speaker output, which should be zero volts.

    You need to search for the service manual by model number.
     
    MarioP2020 likes this.
  3. MarioP2020

    Thread Starter New Member

    Sep 6, 2018
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    Hello Dodgydave!

    Thank you for your reply! It's very much appreciated!

    I am a newb, but have interest in learning more about electronics! I have tried contacting the company that manufactured these Eagle amps, but from what I have read, they are out of business. I searched for the schematics and service manual, but no luck! I did find a schematic for the Eagle 7, but not sure how different it is from the Eagle 2.

    I was going to replace all of the caps, as I have read that over time, they can start to leak or swell when they get old and turn bad. I'm not certain about how long the other components will last such as the transistors, OP-AMPS, diodes, resistors, etc. Also, I have noticed that the 2 main caps, rated at 80,000mfd/50V, appear to have leaked at the bottoms. I have attached a photo of the bottoms. Does this appear to look like faulty/leaky caps?

    What do you think I should do at this point? Once again, many thanks! Mario
     
  4. MarioP2020

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    Sep 6, 2018
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    BUMP
     
  5. JoeJester

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    Did you replaced the component dodgydave had identified earlier?
     
  6. MarioP2020

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    Sep 6, 2018
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    Hello JoeJester!

    I didn't replace yet, as I am not sure where I can locate these Sanken transistors. I tried searching here for the Part Search, but it showed no results found. I was thinking about replacing all of the caps and these transistors, do you think this would be OK? I was just thinking long term as perhaps these are so old they may give me trouble at any given time.

    I'd also like to try and order most of these components at one time if possible. What is your thoughts for this? Thanks for your reply!
     
  7. JoeJester

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    What are your goals? You could replace everything, but that would get expensive. Take a picture of the other transistor next to the defective one. A clear picture with the numbers clearly displayed.

    2SA958 is the complement of 2SC2168

    They form the push-pull drivers of your amplifier


    Don't look for parts here .... use google and get the datasheets. Since you didn't identify where you are, I have no idea of where you can by that transistor.

    On edit ... Where is the 2SA1170 that should be where the yellow circle is?

    PICT1365.jpg
     
    Last edited: Sep 10, 2018
  8. MarioP2020

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    Sep 6, 2018
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    Hi Joe, I am in Louisiana. I did a search on Google and it seems like Ebay has some, but they are rather expensive for the larger transistors.

    I have some photos in my first post above that you should be able to see clearly. Besides the transistors, the smaller caps are not that pricey. Those 2 big mains caps will probably be the most expensive parts. One of those big caps did not discharge, so that may be another issue.

    Do you think that resistors and diodes will last, or should I rebuild the entire board? I am also wondering if I could replace the Sanken transistors with another brand that is more ready available?

    What would you do if this were your amp? Thanks again for your reply! Cheers!
     
  9. MarioP2020

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    Sep 6, 2018
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    Joe, that 2SA1170 that you have circled is there behind a component that I can't identify. That component appears to be mounted on the top of that transistor. Sorry, but I'm not familiar with that set-up.
     
  10. bertus

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  11. MarioP2020

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    Sep 6, 2018
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    Ah! Thanks bro! I learn something new everyday..LOL..They seem cheap enough. I wonder if they would need to be replaced?

    You wouldn't happen to know where I can locate these Sanken transistors, besides Ebay? Thanks for that info! Cheers, Mario
     
  12. bertus

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  13. MarioP2020

    Thread Starter New Member

    Sep 6, 2018
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    Hi Bertus! Thanks so much for that info! Do you think I should do a complete overhaul on this amp? Or just replace the transistor that appears to be bad? Not sure if just replacing one or 2 parts would give a long run time on this amp, as it is around 26 years old. It did get it's mileage..LOL

    Any advice as to what you would believe to be the best thing to do with my situation? Thanks again pal :)

    BR,

    Mario
     
  14. MarioP2020

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    Can someone tell me how I can send a PM here? I just can't figure out how I can message someone..lol
     
  15. MarioP2020

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    Sep 6, 2018
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    I measured the resistance between B/E on transistors and measured 1.292 M ohms. Would this indicated a short? Thanks!
     
  16. JoeJester

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    Measure C to E, both directions. It will be a short.
     
  17. Dodgydave

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    No, but your voltages show the same on B and E, so without a circuit diagram it's difficult to diagnose the problem.
     
  18. MarioP2020

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    Sep 6, 2018
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    I measured C to E like you said, and it showed 706 Ohms.
     
  19. MarioP2020

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    Sep 6, 2018
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    Thanks. I looked all over for a service manual, but can't locate one. :(
    I do have a schematic for an Eagle 7 amp, but not sure if it would help.
    Here it is anyhow. Maybe of help, not sure.
     
  20. JoeJester

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    http://www.eagle-audio.com/upgrades.htm

    Eagle audio recommends you replace all the electrolytic capacitors, but till you solve the problem, you might as well wait.

    Are you measuring those transistors "in circuit" or are you disconnecting them before doing the resistance measurement?

    Eagle 7A Revision 2 maybe someone's personal revisions to the amplifier especially with those pen and ink corrections. Unless you check every component listed on the schematic against the circuit, one will never know.
     
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