Transformer or Something Else?

Discussion in 'Amps [BG]' started by Fitchbass, Feb 6, 2014.


  1. Fitchbass

    Fitchbass

    Joined:
    Mar 17, 2013
    How do you know if your amplifier needs a new transformer? I have an 2001 AMPEG SVT CL sometimes when I turn the standby on it creates a loud popping noise. It is not consistent and I asked a technician about this and he told me that I might need a new transformer. I have brand-new tubes and it and had it biased so I know this is not the issue.
  2. beans-on-toast

    beans-on-toast

    Joined:
    Aug 7, 2008
    Chances are, a transformer is the last thing that you'll need. Find a different tech that knows how to troubleshoot a circuit and isn't so full of doom and gloom.
  3. Fitchbass

    Fitchbass

    Joined:
    Mar 17, 2013
    Ok. Thanks.
  4. B-string

    B-string Supporting Member

    Joined:
    Nov 21, 2008
    Location:
    Lake Havasu City, Az USA
    +1. The only thing that goes "pop" with a transformer is usually the fuse.
    A defective new tube is NOT out of the realm of possibilities by the way.
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  6. beans-on-toast

    beans-on-toast

    Joined:
    Aug 7, 2008
    There are a number of possibilities that should be investigated before suggesting that transformer is the problem. A popping sound can be associated with an output transformer but this is very rare. As was said, even though your tubes are new, one of them can have an issue or the tubes can be badly matched. It could be a bad solder joint, bad capacitor or other component. There are many possibilities.

    It makes a difference if the popping occurs while you are playing or just when you hit the standby switch. Is it a single pop or does it keep popping like pop corn.

    And to be clear, when you say turn the standby on, do you mean "standby off" as in the amp is in playing mode, or do you mean "standby on" as in the amp is not in playing mode but warm up mode. This is confusing.
  7. Fitchbass

    Fitchbass

    Joined:
    Mar 17, 2013
    Sorry, I meant to say it pops when I turn the stand by off into playing mode. The popping is inconsistent, it never lasts more than a few seconds. It had done this prior to having new tubes installed.
  8. BassmanPaul

    BassmanPaul Gold Supporting Member

    Joined:
    Aug 25, 2007
    Location:
    Toronto Ontario Canada
    It could always be arcing in the standby switches contacts. I have seen this before and a 10n 1KV ceramic cap wired across the switch calmed it down.
  9. beans-on-toast

    beans-on-toast

    Joined:
    Aug 7, 2008
    When you come out of standby, the high voltage (B+) is turned on and hits the power tubes. This can make them pop.

    There is a slight chance that the pins on your old tubes were bigger than the ones on the new tubes. If the pins are not making solid contact with the tube socket terminals, there can be an arc which would result in a pop. I've also seen this happen if the tube socket is not clean. Sometimes you apply a product such as deoxit on the socket and it needs to be scrubbed and deoxit reapplied more than once to get it clean. A stubborn bit of oxidation can cause an issue reducing the effectiveness of the electrical connection. Unfortunately, with the CL, getting to the power tube board is a lot of work so some extra bench time is involved.
  10. Fitchbass

    Fitchbass

    Joined:
    Mar 17, 2013
  11. beans-on-toast

    beans-on-toast

    Joined:
    Aug 7, 2008
    That sounds pretty nasty. Spikes like that are not good for your speakers. It would be a good idea to turn the volume down all the way when coming out of standby.

    What I said above about retensioning the power tube sockets and inspecting them for oxidation applies. Given what I heard, I'd also look for carbon deposits on the socket which would indicate arcing. It might be as simple as a bad standby switch or an issue in the standby circuit.

    These sort of problems are difficult to resolve without looking in person. Might be worth it to PM Hodgy and ask if he has a suggestion. It might be a known issue that Loud has a fix for.
  12. Fitchbass

    Fitchbass

    Joined:
    Mar 17, 2013
    Sorry but how do I get in touch with Hodgy!
  13. Fitchbass

    Fitchbass

    Joined:
    Mar 17, 2013
    The volume was completely down on both the master and gain.
  14. beans-on-toast

    beans-on-toast

    Joined:
    Aug 7, 2008
    Hodgy works in customer service at Loud so he will be able to assist you.

    click on this, and send him a private message: http://www.talkbass.com/forum/private.php?do=newpm&u=42323

    Include a pointer to this thread or any other related links. Here is the pointer to this thread: http://www.talkbass.com/forum/f15/transformer-something-else-1052701/. You want to copy paste the link into the message. When he replies, up on the top right of the page where it says private messages, you will see Unread 1. Click on it to see the reply.
  15. beans-on-toast

    beans-on-toast

    Joined:
    Aug 7, 2008
    Yikes! I'd try to get it resolved without too much delay.
  16. Fitchbass

    Fitchbass

    Joined:
    Mar 17, 2013
    Thanks for your help. Hopefully, I can get this resolved right away.
  17. beans-on-toast

    beans-on-toast

    Joined:
    Aug 7, 2008
    It could be also be related to the standby switch itself or a relay. Unfortunately, they are many possibilities.
  18. Fitchbass

    Fitchbass

    Joined:
    Mar 17, 2013
    Well still no ideas on what's going on. Anyone know of a reputable tech that works on SVT's near Nashville?
  19. lowfreq33

    lowfreq33

    Joined:
    Jan 27, 2010
    Location:
    Nashville
    Disclosures:
    Endorsing Artist: Genz Benz Amplification
    Call Rock Block and see who they recommend.
  20. teemuk

    teemuk

    Joined:
    Mar 1, 2011
    Why do you need the stanby switch? A volume control will mute your amp just as effectively, but without arcing at switch terminals, without wearing down the tubes, and without making inconvenient noises. In a musical instrument amp the standby feature is nothing but a fancy mute switch, and apparently in your amp it no longer serves well even as that. Just get rid of idea of using those stupid things. No one really needs them.
  21. Fitchbass

    Fitchbass

    Joined:
    Mar 17, 2013
    Thanks so much. I bypassed the stand by switch and there was no issue. I also read an article where a technician said the standby switch was totally unnecessary.

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