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Is the power LED on the KA-7100 part of the protection circuit?

Discussion in 'Kenwood-Trio/Kensonic-Accuphase' started by Robisme, Jul 31, 2011.

  1. Robisme

    Robisme Sansui Enthusiast Subscriber

    Messages:
    11,793
    Location:
    Martinez California
    I am working on a KA-7100 that did not come out of protection. I tested the outputs, drivers, DC offset at the relay, and bias. All OK.

    I decided to replace the power LED before I went any further, and when I connected the new one (I had it powered up) it came out of protection. Disconnected the LED and back into protect it went. Reconnected LED and out of protect again.

    Installed the LED and it works fine. I don't have the schematic.

    Rob
     

     

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  2. Sir.Byrd

    Sir.Byrd Lunatic Member

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    Check the old LED, if it is dead I would imagine it was part of the protection circuit.
     
  3. EchoWars

    EchoWars Hiding in Honduras

    Messages:
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    Location:
    Kansas City
    Yes, the pilot LED is part of the AC loss detect circuitry...if the LED goes open, the protect circuit behaves as if AC power has been lost and opens the speaker relay.

    I had forgotten that little tidbit of info...has been a while since I saw a 7100 with a duff LED.
     
  4. Robisme

    Robisme Sansui Enthusiast Subscriber

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    Thanks.

    I would think not many amps are configured that way.

    Rob
     
  5. TonioK

    TonioK AK Subscriber Subscriber

    Messages:
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    Location:
    Carbondale Illinois
    Hi, I’m new here.
    I need a new LED for my KA-7100. I pinched the wire while putting it back together after a recap and killed it.
    I put in a random LED I found in my garage to see if it would work and it does except now the protection relay does it’s thing after about 4 minutes of playing a CD. I tried to set the bias before connecting speakers but the relay would only stay on for about 10 seconds.
    Can someone please advise me on the correct LED? I bought this amp new in 1978 and I want to get it working again for sentimental reasons. Thank you!
     
  6. avionic

    avionic " Black Knights " Subscriber

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    Last edited: Nov 25, 2018

     

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  7. avionic

    avionic " Black Knights " Subscriber

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    What test points were you using?
     
  8. TonioK

    TonioK AK Subscriber Subscriber

    Messages:
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    Location:
    Carbondale Illinois
    The speaker terminals. It reads 2.3V then rises to about 2.6 when the relay cuts it off in about 30 seconds. I connected speakers and a CD player and it works for 3 or 4 minutes before the relay shuts it off.
     
  9. avionic

    avionic " Black Knights " Subscriber

    Messages:
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    You are actually trying to adjust the center voltage(dc offset) not the bias. Can't adjust bias at the speaker connections.
     
  10. TonioK

    TonioK AK Subscriber Subscriber

    Messages:
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    Location:
    Carbondale Illinois
    I don’t see the picture you linked. I’ll try and post what I used. It came out of a bug zapper that looks like a little tennis racket.
     

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  11. TonioK

    TonioK AK Subscriber Subscriber

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    Location:
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    Sorry, I see it now. I thought you wanted to see the replacement. Here is the original...
     

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  12. avionic

    avionic " Black Knights " Subscriber

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    Does this do the same for the left channel as well as the right channel?
     
    TonioK likes this.
  13. avionic

    avionic " Black Knights " Subscriber

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  14. TonioK

    TonioK AK Subscriber Subscriber

    Messages:
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    Location:
    Carbondale Illinois
     
  15. TonioK

    TonioK AK Subscriber Subscriber

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    Location:
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    Thank you for helping me. I am not a tech so I use the wrong words sometimes.
     
  16. avionic

    avionic " Black Knights " Subscriber

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    That multicomp diode looks like the same diode.
     

     

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  17. TonioK

    TonioK AK Subscriber Subscriber

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    Location:
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    Yes, about the same both channels
     
  18. TonioK

    TonioK AK Subscriber Subscriber

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    Location:
    Carbondale Illinois
    After reading some other posts I thinking my problem might not be the LED at this point.
     
  19. avionic

    avionic " Black Knights " Subscriber

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    PM sent
     
  20. avionic

    avionic " Black Knights " Subscriber

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    I'm thinking that as well.
     

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