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Adcom 5400 amplifier blowing all fuses

Discussion in 'Audio' started by Audiofreak1, Sep 20, 2018.

  1. Audiofreak1

    Audiofreak1

    32
    2
    Sep 20, 2018
    ok now before I installed the new caps and I had a problem where it would make loud spikes of noise for two minutes. After that it was fine. Now I bought new caps and inrush current limiters. The inrush limiters I installed are sg26 5ohm 12 volt and the caps are 15000uf chemi con 105degrees 4 of them i put them in the same as I took them out. Put everything back together and plugged it in and both protection light came on for 2 seconds before I powered it on. The. I flipped the switch and all fuses blew except the small board with the transformer on it that’s the only fuse that did not blow. Check wiring somewhat I know I labeled everything and plugged it back how it was. I am at a loss here need some help. If anyone can help I would appreciate it.
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    9,053
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    Nov 17, 2011
    You may have gotten the polarity of the capacitors wrong. Inserted backwards electrolytic capacitors can draw a lot of current. If that is the case, the incorrectly oriented capacitor(s) is most likely unusable now.
     
  3. Audiofreak1

    Audiofreak1

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    Sep 20, 2018
    I was sitting here thinking and I know what I did. I am just hopping that I did not destroy too much if anything at all. I switched the two connections on the bridge rectifier so basically I made the ground a positive I think. Well I will take care of this tomarrow and report back.
     

    Attached Files:

  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    If it's a valve amplifier, you may be ok.

    But I guess it's solid state, right?

    It could be expensive to the point of it being uneconomic to repair.
     
  5. Audiofreak1

    Audiofreak1

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    Sep 20, 2018
    Yeah I figured but it was only on for maybe two seconds so I hope it’s ok. And I think only one side was hook up wrong
     
  6. Harald Kapp

    Harald Kapp Moderator Moderator

    9,053
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    Nov 17, 2011
    :(
     
  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,160
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    That's about a thousand times longer than needed :-(

    Unfortunately, only one side needs to be the right way around :-(
     
  8. VenomBallistics

    VenomBallistics

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    Aug 30, 2018
    Audiofreak1 likes this.
  9. Audiofreak1

    Audiofreak1

    32
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    Sep 20, 2018
    Well I got it all together again tested the bridge rectifiers they all read .471 to .493 diode test. And now when I put the plug in the right side protection lights up for 2 3 seconds then shuts off before it is even turned on the left side does nothing. Now I checked the positive and negative fuse lines to ground and I get the same reading on both of them. .471 and the other one goes to .108 to 1.980 then the meter shows nothing. I am pretty sure I had the bridge rectifier hooked up wrong on one of them. Now everything is hooked up right. I am kinda afraid to turn it on at this point. Any input on what I need to do next.
     
  10. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,160
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    Google "dim bulb tester".
     
    Audiofreak1 likes this.
  11. Audiofreak1

    Audiofreak1

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    Sep 20, 2018
    Well she power up not bad light so far. I had a light on the right side but I figured that out the dc offset was way high so distortion was showing. Now no bad lights. I still need to get 4 amp fuses for it so I can run a set of speakers on it. Need to let her warm up good them I am going to check the bios. After that try it out. Hope all works so far so good no signs of issues. The real test will to put it under load and see how she goes. I will keep updating as I go. So far thanks to all who read my post and gave a hoot. Apreciate it :)
     
  12. Audiofreak1

    Audiofreak1

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    Sep 20, 2018
    C280762A-D410-455B-9036-8B7DD578311F.jpeg
    I made one not the fancy kind though. Parts laying around my garage had everything. Worked out good will be using in the future. Thank :)
     
  13. Audiofreak1

    Audiofreak1

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    Sep 20, 2018
    Well good news no damage was done. Amp plays fine. Adjusted dc voltage and bios to spec. It still has the original issue. When I turn the amp on it has a distortion light on the right channel for about 2 minutes. Then goes away. Not dramatically it fades over that time. Any suggestions would be appreciated. And if I have speakers connected to the amp sharp loud noises come out of the speakers like static intermittent spaced
     
  14. VenomBallistics

    VenomBallistics

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    Aug 30, 2018
    nice empire of dirt ya got there :D
    I keep a 282iQ in my patch bay.
    Can you remove the grill from your speakers so that you can observe them at fireup?
    see if you have a woofer being pushed out or sucked in and held while it wakes up.

    The light, and probably the noise as well, is due to a signal level being detected that is in a range that the distortion detection circuit assumes will drive the output to the rails (and probably does even if only momentarily).
    which is the bread and butter of distortion, be it THD in a HiFi amp or Marshall Stack cranked to 11 for your face melting pleasure.

    Back trace that light and see what it's "listening" to.
    These things don't get better with age, only more expensive
     
    Audiofreak1 likes this.
  15. Audiofreak1

    Audiofreak1

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    Sep 20, 2018
    The woofer gets sucked in.
     
  16. VenomBallistics

    VenomBallistics

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    Aug 30, 2018
    Okay ... that's bad. Real bad.
    basically at power on, its dumping everything the output stage can deliver from the - rail through the speaker.
    start from the OPS and work back
     
  17. Audiofreak1

    Audiofreak1

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    Sep 20, 2018
    Thanks for the reply I order all the electrolodic caps for the boards and going to start there. Then diodes check and replaced. And if still there new output trans. And to answer the question fully the woofer gets sucked in but comes back out right away slowly.
     
  18. VenomBallistics

    VenomBallistics

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    Aug 30, 2018
    that should work, but as I look through a pile of designs ... the next place to look is the VA stage and bias generator. Most seem to have caps large enough to do what you describe ... good news is that the parts are fairly cheap in this part of an amp
     
  19. Audiofreak1

    Audiofreak1

    32
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    Sep 20, 2018
    I will do that venom! And yes I am seeing parts are not that expensive for this amp. Here is the scamatics never like adcoms prints they work but could of drew it better in my opinion. I have all the electrolodic caps now so once I get them replaced and a few other parts checked I will report back as I go. Want to put information up for anyone with similar problems. :)) 0E27B471-9051-4552-A4B7-63D0B97A336A.png
     
    Last edited: Oct 15, 2018
  20. VenomBallistics

    VenomBallistics

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    Aug 30, 2018
    yeah ... the most expensive part is the power transformer. the next are the output transistors, which kinda run the gambit from "wow thats all" on up to "thank you sir may I have another".
    My home brew solid state guitar amp uses 4 each MJ15003 and MJ15004. Its not quite a 1940's British orphanage kinda floggin but it is a kick in the nuts
     
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