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  • Adcom GFA 555 amp repair shop suggestions........


    I have a Adcom GFA-555 that has played without a problem for over 20 years until now....... no problem while playing at any level but everytime at power down after about 30 sec. to a minute after being switched off I hear a high pitched squeel from the right channel that lasts about 3 to 5 seconds...... a capacitor discharging??? I repeat that there is NO problems at all while playing that I can hear or have noticed. A friend of a friend recommended to have the "bias" checked?? and that a competent audio repair shop could do this along with checking the rest of the internal components as this particular amp probably needs a complete inspection/tune up anyway after 20 years of use. Can anyone suggest a repair shop for an older amp like this one??? I have always liked this amp and would like to keep it as until now this amp has never had any problems and has been pounded endlessly. Since I have it powered thru a Panamax line conditioner I use the Panamax power on/off switch to turn the amp on and off. A friend has recommended to leave it powered on all the time but I have never done this since buying it and presently use it to drive a pair of WJ's Veritas with the HiVi planar tweeters. Thanks for any replies


    (Originally posted by: Mark Milner)

  • #2
    Re: Adcom GFA 555 amp repair shop suggestions.....


    Without a schematic, I can't say for sure, but typically amplifiers will have a relay that disconnects the speakers during power up and at power down. Do you hear a relay click after a few seconds when you first turn it on?

    If indeed there are relays incorporated in the design, then I'd say the amp is fine, but one of the relays is stuck 'on'. -It may be a simple fix, and not require a virtuoso repair tech to repair it.

    C
    Curt's Speaker Design Works

    "It is the mark of an educated mind to be able to entertain a thought without accepting it."
    - Aristotle

    Comment


    • #3
      Re: Adcom GFA 555 amp repair shop suggestions.....


      My Adcom GFA-555 has done this since 1999. Still works perfectly.

      -Chris

      > I have a Adcom GFA-555 that has played
      > without a problem for over 20 years until
      > now....... no problem while playing at any
      > level but everytime at power down after
      > about 30 sec. to a minute after being
      > switched off I hear a high pitched squeel
      > from the right channel that lasts about 3 to
      > 5 seconds...... a capacitor discharging??? I
      > repeat that there is NO problems at all
      > while playing that I can hear or have
      > noticed. A friend of a friend recommended to
      > have the "bias" checked?? and that
      > a competent audio repair shop could do this
      > along with checking the rest of the internal
      > components as this particular amp probably
      > needs a complete inspection/tune up anyway
      > after 20 years of use. Can anyone suggest a
      > repair shop for an older amp like this
      > one??? I have always liked this amp and
      > would like to keep it as until now this amp
      > has never had any problems and has been
      > pounded endlessly. Since I have it powered
      > thru a Panamax line conditioner I use the
      > Panamax power on/off switch to turn the amp
      > on and off. A friend has recommended to
      > leave it powered on all the time but I have
      > never done this since buying it and
      > presently use it to drive a pair of WJ's
      > Veritas with the HiVi planar tweeters.
      > Thanks for any replies

      Comment


      • #4
        Re: Adcom GFA 555 amp repair shop suggestions.....


        > I have a Adcom GFA-555 that has played
        > without a problem for over 20 years until
        > now....... no problem while playing at any
        > level but everytime at power down after
        > about 30 sec. to a minute after being
        > switched off I hear a high pitched squeel
        > from the right channel that lasts about 3 to
        > 5 seconds...... a capacitor discharging???

        You turn your amp off? I got mine in '85. It gets turned off and unplugged if I move or if a storm is coming, or if I am travelling. My 555 is very quiet when I do turn it off. I hope this is not something I can expect at any time now since it is old, as well.

        Comment


        • #5
          Re: Adcom GFA 555 amp repair shop suggestions.....


          everytime at power down after
          > about 30 sec. to a minute after being
          > switched off I hear a high pitched squeel
          > from the right channel that lasts about 3 to
          > 5 seconds......

          You mean the quiet squeal that sounds like a mouse farting? That's normal.


          (Originally posted by: BFB)

          Comment


          • #6
            Re: Adcom GFA 555 amp repair shop suggestions.....


            Could be a leaky cap... I'd consider a cap upgrade and bias check/adjust. The only tech shop I've used is Vintage Amp Repair but they specialize in older Forte and Threshold gear. They're a bit pricey but Jon does very good work. He repaired a GFA-555 for me once. How much are you prepaired to spend for a repair/upgrade?

            > I have a Adcom GFA-555 that has played
            > without a problem for over 20 years until
            > now....... no problem while playing at any
            > level but everytime at power down after
            > about 30 sec. to a minute after being
            > switched off I hear a high pitched squeel
            > from the right channel that lasts about 3 to
            > 5 seconds...... a capacitor discharging??? I
            > repeat that there is NO problems at all
            > while playing that I can hear or have
            > noticed. A friend of a friend recommended to
            > have the "bias" checked?? and that
            > a competent audio repair shop could do this
            > along with checking the rest of the internal
            > components as this particular amp probably
            > needs a complete inspection/tune up anyway
            > after 20 years of use. Can anyone suggest a
            > repair shop for an older amp like this
            > one??? I have always liked this amp and
            > would like to keep it as until now this amp
            > has never had any problems and has been
            > pounded endlessly. Since I have it powered
            > thru a Panamax line conditioner I use the
            > Panamax power on/off switch to turn the amp
            > on and off. A friend has recommended to
            > leave it powered on all the time but I have
            > never done this since buying it and
            > presently use it to drive a pair of WJ's
            > Veritas with the HiVi planar tweeters.
            > Thanks for any replies

            Comment


            • #7
              Re: Adcom GFA 555 amp repair shop suggestions.....


              Did you change speakers recently? The funny squeal during power-down is the amp going unstable (oscillating) as the bias voltages fall. Stability is load dependent. It is also dependent on the rate (and order) in which the internal bias voltages/currents fall and may change as electrolytics age. I have a Flame Linear that squeals during power down with some speakers but not others.

              Comment


              • #8
                Re: Adcom GFA 555 amp repair shop suggestions.....


                > I have a Adcom GFA-555 that has played
                > without a problem for over 20 years until
                > now....... no problem while playing at any
                > level but everytime at power down after
                > about 30 sec. to a minute after being
                > switched off I hear a high pitched squeel
                > from the right channel that lasts about 3 to
                > 5 seconds...... a capacitor discharging??? I
                > repeat that there is NO problems at all
                > while playing that I can hear or have
                > noticed. A friend of a friend recommended to
                > have the "bias" checked?? and that
                > a competent audio repair shop could do this
                > along with checking the rest of the internal
                > components as this particular amp probably
                > needs a complete inspection/tune up anyway
                > after 20 years of use. Can anyone suggest a
                > repair shop for an older amp like this
                > one??? I have always liked this amp and
                > would like to keep it as until now this amp
                > has never had any problems and has been
                > pounded endlessly. Since I have it powered
                > thru a Panamax line conditioner I use the
                > Panamax power on/off switch to turn the amp
                > on and off. A friend has recommended to
                > leave it powered on all the time but I have
                > never done this since buying it and
                > presently use it to drive a pair of WJ's
                > Veritas with the HiVi planar tweeters.
                > Thanks for any replies

                It's not bias. Nobody on this board knows anything about your problem or can help you fix it. You're best left to taking it to a competant repair person if it bugs you that much.

                Comment


                • #9
                  Snap Crackle Pop - Rice Crispies *NM*



                  Comment


                  • #10
                    Originally posted by panterra View Post
                    Re: Adcom GFA 555 amp repair shop suggestions.....


                    > I have a Adcom GFA-555 that has played
                    > without a problem for over 20 years until
                    > now....... no problem while playing at any
                    > level but everytime at power down after
                    > about 30 sec. to a minute after being
                    > switched off I hear a high pitched squeel
                    > from the right channel that lasts about 3 to
                    > 5 seconds...... a capacitor discharging???

                    You turn your amp off? I got mine in '85. It gets turned off and unplugged if I move or if a storm is coming, or if I am traveling. My 555 is very quiet when I do turn it off. I hope this is not something I can expect at any time now since it is old, as well.
                    Wow, old thread. Just a follow up to my post back in 2007. My amp had finally given up the ghost. It was from a surge of just plugging it in while the power switch was in the on position. So it lasted almost 30 years. I went ahead and got a Yamaha 5.1 receiver from Parts Express - thank you very much, it is not worth having it recapped at over $500 when I could get an Emotiva amp for $400 which is after their price increase from $350 for their 150W/ch. I had enough speakers built to actually now have a 5.1 HT system. The tuner section on the Yamaha receiver is not the best, at least not as good as the one on the 30yr old Adcom PreAmp/tuner GTP 500. So I just hooked up the GTP 500 to the AV4 input so I still have a use it. I also use the phono amp on the Adcom GTP 500 so I didn't lose that capability because the Yamaha doesn't seem to have one.

                    Comment


                    • #11
                      Here's a link to a folder on my google drive with two versions of the GFA-555 service manual, two versions of the schematic and the users manual (I think there's a GFA-555 and a GFA-555 II). They might come in handing for anyone attempting a repair. I didn't see output relays in a quick scan of schematic. Following the link, right click on a document and select download (near the bottom of the drop down menu). Good luck and have fun.

                      https://drive.google.com/drive/folde...kU?usp=sharing

                      Comment


                      • #12
                        Originally posted by panterra
                        Wow, old thread. Just a follow up to my post back in 2007. My amp had finally given up the ghost. It was from a surge of just plugging it in while the power switch was in the on position. So it lasted almost 30 years. I went ahead and got a Yamaha 5.1 receiver from Parts Express - thank you very much, it is not worth having it recapped at over $500 when I could get an Emotiva amp for $400 which is after their price increase from $350 for their 150W/ch. I had enough speakers built to actually now have a 5.1 HT system. The tuner section on the Yamaha receiver is not the best, at least not as good as the one on the 30yr old Adcom PreAmp/tuner GTP 500. So I just hooked up the GTP 500 to the AV4 input so I still have a use it. I also use the phono amp on the Adcom GTP 500 so I didn't lose that capability because the Yamaha doesn't seem to have one.
                        I don't know who made you a quote of $ 500, but that is crazy. It can be done much, much cheaper and you will have a better amp.
                        craigk

                        " Voicing is often the term used for band aids to cover for initial design/planning errors " - Pallas

                        Comment


                        • #13
                          Originally posted by craigk View Post
                          I don't know who made you a quote of $ 500, but that is crazy. It can be done much, much cheaper and you will have a better amp.
                          http://bigskyaudiomt.com/index.php?pr=ADCOM_GFA_555_II

                          If you have any specifics of where this place is that you are thinking of, it would be greatly appreciated.

                          Comment


                          • #14
                            George Meyer AV in Los Angeles is extremely competent and charges fair rates for professional service. Not cheap, but they know their stuff and have the right equipment. They are often busy, i.e. they are not fast due to backlog. I've been there in person at both their new and old facilities.
                            --Derek

                            Comment

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