Jump to content

Help diagnosing my Adcom GFA-535


Recommended Posts

Hi, all!


Today I've run into a problem with my GFA-535. When I went to switch back to it from a different amp, I noticed an unusual buzz start to come from my subwoofer when I turned it on. Not wanting to risk my Heresies in case something was wrong (glad it has speaker selectors!), I plugged one of my B-10s into the left channel on the other set of outputs. Once patched in, it revealed a loud, nasty static buzz (I also tested the other channel.)


It only does it when it has something connected to either input. It could be a bare wire and it happens. I connected my iPhone as a source when trying to single out the amp from the preamp and it still did this, without seeming to react to the signal from the phone. It also seems to certainly cause feedback back through the inputs, as my subwoofer only buzzed when the amp and preamp were connected.


Now, a few things that happened recently. First, one of the metal rings surrounding the right channel RCA plug had come out when unplugging it recently, leaving just bare plastic. I always assumed these were cosmetic, since the other one was never there (I received the amp that way) and it was never a problem.


I also I believe I plugged the pre back in with the preamp still on (and the amp off).


How could I go about diagnosing this, and does it seem like something I could fix myself? I like the 535, and while it would be fun to shop for a new amp, I wouldn't be happy to trash this one. Thanks!

Link to comment
Share on other sites

  • 4 weeks later...
  • 2 months later...
  • 2 weeks later...

Glad you've got it going!


I've got a NAD integrated amp that has the same 60hz tone. Mine started with a lightning strike. Clipping light now stays on. No part of the amp will work without the background noise. Sheeze, where to start? I'm guessing power supply. Maybe a power supply cap has shorted to ground? Any suggestions appreciated. 



Link to comment
Share on other sites

lightning strike just might be the kicker here... I would open it up and look for a burned up ground trace. If it is working and humming, something that was (is) connected to it may have burned up a signal ground trace.


I say this because it is working. If it was a main ground in the amp or supply, It would not work.

  • Like 1
Link to comment
Share on other sites

With Paul's troubleshooting suggestion I've separated this NAD 3130 integrated amp from all other equipment and taken it to another room and I can report the 60hz tone is gone. That's the good news. This remaining issue is that one channel is about 1/2 volume of the other? I don't really hear any new noise though? Never has been a dead quiet amp for that matter. A visual inspection reveals nothing.  No surface mount technology present on this one. All traces look good. No fat caps. The amp has 4 main transistors. 2) 2N3055 and 2) MJ2955. Maybe a transistor has failed?


Link to comment
Share on other sites

That would be a dirty relay. Flip it with your finger, and I bet you can make it do crazy things. You can pop off the cover of these relays carefully, and clean the contacts.


Now you get to figure out what component is humming! Preamp most likely, same scenario, check the jacks and the traces related to them.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...