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5E3 Almost there, just a couple of questions before power up.

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  • #16
    If it is one of the filter caps you could take two leads with clips and clip another cap in parallel to the suspicious one. If that makes a difference, it's probably a bad cap.

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    • #17
      Originally posted by txstrat View Post
      ...Your goal is, that no currents have the same path to this point of the chassis, the star ground. This point should preferably be at one of the PT bolts as you did. ...
      I sort of agree with the first part to some degree but why should this "tranny bolt" be preferable?
      Bruce

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

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      • #18
        I still have hum,

        I took a cap and jumped around the filter caps, with no change, bypass caps, no change and coupling caps, still no change.

        I removed the tone stack, no change, possibly worse.

        I'm at my whit's end here. and things seem to be getting worse. the tone was almost acting like a volume, and if turned up, the hum is magnified drastically.

        Now it sounds like it's really buzzing rather badly when playing though it.

        I'm to the point where I want to tear it out and start one channel at a time, front to end, and give it a go.

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        • #19
          Originally posted by Bruce / Mission Amps View Post
          I sort of agree with the first part to some degree but why should this "tranny bolt" be preferable?
          As far as I read the star ground should be far away from the input jacks.
          That's where the PT mostly is. And there are 4 bolts you can conveniently use for your ground lug.

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          • #20
            Originally posted by Leif H View Post
            I'm to the point where I want to tear it out and start one channel at a time, front to end, and give it a go.
            I'm at this point as well with my Portaflex clone.
            If you followed the weber layout there should be no hum or at least no hum to worry about. Check if you forgot a ground connection at some point. Check the solder joints and if all connections are soldered properly. Check the heater wires (do you have a heater CT or virtual tap? - if it's a VT are the resistors OK?).
            Get a closer look around the PI (and the power tubes), since pulling the PI tube reduced the hum while pulling the preamp tubes didn't change anything as you mentioned before.

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            • #21
              Originally posted by txstrat View Post
              I'm at this point as well with my Portaflex clone.
              If you followed the weber layout there should be no hum or at least no hum to worry about. Check if you forgot a ground connection at some point. Check the solder joints and if all connections are soldered properly. Check the heater wires (do you have a heater CT or virtual tap? - if it's a VT are the resistors OK?).
              Get a closer look around the PI (and the power tubes), since pulling the PI tube reduced the hum while pulling the preamp tubes didn't change anything as you mentioned before.
              Don't say that, that's one of my next projects, B15N pre-amp for a bass amp.
              Last edited by Leif H; 11-12-2009, 05:38 PM.

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              • #22
                Yippie kai yay!

                We're done, the hum beast is silenced!

                THANKS GUYS!

                I fixed the star ground, tidied up the heater wiring and put the virtual center tap on the heater wires. And was done in time to "warm her up a bit"

                I'm grinnin like the cheshire cat.

                Thanks again for all your help, this board is a great resource and full of people who can offer the obscure that comes only with experieince!

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