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Weber 5E7 build. Choke arcing when signal applied

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  • Weber 5E7 build. Choke arcing when signal applied

    I have a Weber 5E7 kit build done by an amateur that was brought to me to troubleshoot. The amp powers up fine, voltages acceptable across the entire amp but no sound is heard at the speaker. However, when a audio signal is applied, the choke clicks and B+ voltage drops. With the volume almost wide open there is faint sound through the speaker. I did find and cure a Output transformer screw that was intermittently shorting the B+ to ground so I'm not sure what damage may have been done to the transformer or choke by the builder. I've subbed a resistor for the choke but nothing changed. I also subbed a known good OT, no change. I've been over the entire amp with the Weber schematic and layout and I can't find any errors. Anyone have any suggestions what to look for?

  • #2
    Probably there is an error with the output transformer connections to the speaker socket.
    Support for Fender, Laney, Marshall, Mesa, VOX and many more. https://jonsnell.co.uk
    If you can't fix it, I probably can.

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    • #3
      I suspect the choke ticks because something after the choke is arcing to ground. The sudden current draw through the choke makes it convulse. Just my thought.

      The amp sits there powered OK? APply some signal and trace it through the amp with a scope.

      But THE question: he built it. Did it EVER work right? Or has it been like this since day one? I'd wager he made a wiring error and it can be had to spot. On eyelet boards everything can LOOK so proper.
      Education is what you're left with after you have forgotten what you have learned.

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      • #4
        Agree with Jon, sounds like the amp is doing work, and B+ dropping, just nothing getting to the speaker. Could be as simple as speaker connected to 'ext.spkr.' jack rather than 'spkr' jack (which has shunt to ground). Or miswired speaker jacks.

        layout: https://tedweber.com/media/kits/5e7_layout.jpg
        schematic: https://tedweber.com/media/kits/5e7_schem.jpg
        Originally posted by Enzo
        I have a sign in my shop that says, "Never think up reasons not to check something."


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        • #5
          Jon Snell and g1, you nailed it. Extension speaker jack wired up backwards. I wired it up properly and the amp sings! Enzo, this thing was littered with problems. Horrible soldering, bias supply wired wrong, poor grounding throughout the amp, intermittent rectifier tube, speaker jacks miswired. I appreciate your help, gentlemen.
          Last edited by jvm; 05-02-2022, 09:13 PM.

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