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Crazy motorboating issue, Fender 5D5. Help!

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  • Crazy motorboating issue, Fender 5D5. Help!

    Hi all,

    I am trying to root out an issue that I've never seen before, and it's driving me crazy. Could use some help!
    I am building a point to point Fender 5D5 clone on the chassis of an old Knight PA amp. My issue is bizarre: With either one and only one of the 6L6 output tubes seated, I'm getting normal operation. Everything sound's fine, quiet, and good, as long as I'm only using a single tube.
    However when I install both output tubes, crazy motorboating starts as soon as I hit power and the tubes warm up.

    I have tried to eliminate all the variables I could think of:
    1. The power tubes I"m using are all good. I have swapped in or out six-seven tubes, in both sockets. No difference in the issue.
    2. I was reusing the original octal sockets for this build. I have since removed both of them and installed quality new sockets in their place.
    3. I have checked, re-checked and checked again, five or six times, the wiring throughout the entire amp. Everything is correct.

    I'm thinking at this point that it's got to be some kind of lead dress issue. Can anyone take a look at the photo and tell me if you see any red flags with respect to lead dress? Or offer any suggestions? I'm all ears!

    http://www.thevintagesound.com/ffg/s..._5d5_schem.gif
    Attached Files

  • #2
    Hi, welcome.


    Please only post once for a new thread. I already replied over in your other thread.
    Education is what you're left with after you have forgotten what you have learned.

    Comment


    • #3
      Post a link to the other thread? I don’t see any other with a similar title.
      --
      I build and repair guitar amps
      http://amps.monkeymatic.com

      Comment


      • #4
        Originally posted by xtian View Post
        Post a link to the other thread? I don’t see any other with a similar title.
        Hi,

        I had also posted it here:
        Crazy motorboating issue, Fender 5D5. Any suggestions? | Telecaster Guitar Forum

        As of now the problem's fixed. It was (as usual) something I never suspected and was surprised to find. Thanks! See the link above, it goes into it. Thanks!

        Ted

        Comment


        • #5
          Thank you for clarifying.
          "Take two placebos, works twice as well." Enzo

          "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

          "If you're not interested in opinions and the experience of others, why even start a thread?
          You can't just expect consent." Helmholtz

          Comment


          • #6
            Did you not post a thread in both Maintenance and here, repair plus also in Debugging your build?

            My post in the debugging thread was to suggest the primary OT wires were reversed.
            Education is what you're left with after you have forgotten what you have learned.

            Comment


            • #7
              The cause of the problem was a wiring error, he discussed it on another forum here: Crazy motorboating issue, Fender 5D5. Any suggestions? | Telecaster Guitar Forum
              Originally posted by Enzo
              I have a sign in my shop that says, "Never think up reasons not to check something."


              Comment


              • #8
                Thanks. I went to the link because you provided it. Mostly I was just taking a smartass opp
                "Take two placebos, works twice as well." Enzo

                "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

                "If you're not interested in opinions and the experience of others, why even start a thread?
                You can't just expect consent." Helmholtz

                Comment

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