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  • Capacitor discharge

    Hi, i just finish to build my 5E3. All is ok, tone is amazing .

    I noticed that when i turn off the amp, the 3 x 16uf/475v capacitors begin to discharge. After one night i just have 5v on B+ ! when i look the schematic, i don't find a way to this capacitors to discharge. So ?

    kind regards.

  • #2
    Why do you need them to discharge? just don't touch the hot ends and you'll be OK.

    If you want to discharge them to work on the amp, power down & connect a jumper wire from pin 1 or 6 of a 12AX7 to ground & wait 30 seconds, now the amp is safe to work on. Remove jumper before powering up.

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    • #3
      I don't need them to discharge, they discharge themselves !

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      • #4
        Schematics show 'idealised' perfect components. In the real world, each component will have it's own sub schematic / equivilant circuit, containing capacitive, resistive and inductive elements.
        Your B+ caps have imperfect insulation between the capacitive electrodes. It's par for the course with electrolytic caps, you'll see it specified in the manufacturer's data sheets as a 'maximum leakage current', and is often related to the product of the capacitence and voltage rating.
        Unless the caps are getting warm just with the B+ voltage across them, don't worry about it.
        Non electrolytic caps are now available with suitable ratings for B+ reservoir/decoupling use, and these will have much better insulation, so will maintain the B+ level for longer after switch off, but they are much more expensive.
        My band:- http://www.youtube.com/user/RedwingBand

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        • #5
          Well, you WANT them to discharge quickly after switchoff, so they don't shock you or blow the tip off your soldering iron.
          "Enzo, I see that you replied parasitic oscillations. Is that a hypothesis? Or is that your amazing metal band I should check out?"

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          • #6
            The tubes are probably discharging the capacitors. They continue to draw some current until they've cooled down.

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            • #7
              Even with just the 5Y3, capacitors discharge themselves when the amp turn off.

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              • #8
                Originally posted by bluescaster View Post
                Even with just the 5Y3, capacitors discharge themselves when the amp turn off.
                Leaving your meter connected will discharge the caps.......eventually.
                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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