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  • #31
    Voltages will drop down when the tubes are installed. The voltages you see on schematics are only valid when all tubes are installed and the standby switch is in the play mode.
    WARNING! Musical Instrument amplifiers contain lethal voltages and can retain them even when unplugged. Refer service to qualified personnel.
    REMEMBER: Everybody knows that smokin' ain't allowed in school !

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    • #32
      Thanks loud, you have been a big help!
      John

      I need more practice, not more gear.

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      • #33
        Before you test this amp with all the tubes installed... (nobody can really help with voltages unless the tubes are all installed).... make sure you set the level of your negative bias voltage (you said it would be adjustable), to the deepest negative voltage the pot will allow.
        I know this is an old thread but that "unloaded" 400vdc mentioned previously with no tubes is going to end up being pretty low for this amp unless there is a wiring error, test error or there is something I missed.
        You still might be buying a new power transformer and the Weber 798 is good enough for this project.
        Bruce

        Mission Amps
        Denver, CO. 80022
        www.missionamps.com
        303-955-2412

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        • #34
          Thanks Bruce. It's an old thread that I revived after setting the amp aside for a few months to work on some other projects. I'll make sure to test as you described. If a new transformer is needed, I'll know what to get.
          John

          I need more practice, not more gear.

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          • #35
            After rewiring the grids, I put tubes in the amp and fired her up. No smoke, no smell... and no sound. I'm going to run back through the solder joints, re-check the wiring, swap tubes, and then print a voltage chart. A quick check revealed very high voltage on the plates of the preamp tubes.
            Last edited by Travst; 04-04-2012, 03:13 PM.
            John

            I need more practice, not more gear.

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            • #36
              To put a period on this project, I did some checking and couldn't spot the problem. Fortunately, I have a great tech in town and dropped it by his shop. Sam (Samamp) spotted the grounding error quickly and brought the amp to life. He also worked out a better grounding scheme and the Super is dead quiet.

              Thanks for all the help, guys. I learned a great deal in the course of the project and your assistance was invaluable!
              John

              I need more practice, not more gear.

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              • #37
                Travst - Can you share the grounding scheme for your Super ? One Star or Multiple Star ?

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                • #38
                  Originally posted by harojs View Post
                  Travst - Can you share the grounding scheme for your Super ? One Star or Multiple Star ?
                  I'll get a pic when I get back from hunting.
                  John

                  I need more practice, not more gear.

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