Superlead has a static-y sound, what could it be....

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by michael.e, Dec 18, 2009.

  1. michael.e

    michael.e Supporting Member

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    Okay....
    The amp has this sound coming from it. It is at one volume, none of the preamp controls affect it. The volume controls do not affect it.
    It sounds almost like a broken record. It has this thick wooshy sound and a consistent crackel.
    I changed out all power tubes, no change.
    I switched out all preamp tubes, no change.
    Hitting [gently] the side/top of the amp does nothing to affect it.
    Touching/moving any outer componentry does not affect it.

    It is moderately loud and again, the volume controls, plugging in an instrument, nothing, nothing changes it.

    What do you think?

    Thanks!
     
  2. WaltC

    WaltC Member

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    Old Super Lead or new "Super Lead"? My initial guess would be bad solder joint, cracked resistor, plate load resistor w/ absorbed moisture. Those would be the things I looked at first.

    Any internal questionable issues? toasted resistor, charred spot on the turret board?
     
  3. Roe

    Roe Member

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    check grounding points and the caps
     
  4. michael.e

    michael.e Supporting Member

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    Grounding points have been checked, solder joints have been checked. This is a '74 Superlead.

    It has this sound like something is floating away from spec.
     
  5. reaiken

    reaiken Member

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    The best way to troubleshoot it is to narrow it down:

    (1) Pull all three preamp tubes out - does it still make the noise? If so, it is in the output tube section, power supply, bias supply, or fuse/fuse holder or switches (standby switches sometimes cause noise, as do loose HT fuses).

    (2) If it doesn't make the noise with all three preamp tubes out, put back only the phase inverter tube. Does it make the noise now? If so, it is in the phase inverter section or feedback network/presence control.

    (3) If it doesn't make the noise with just the phase inverter tube in, put in the second preamp tube. Does it make the noise now? If so, it is in that area of the circuit. If not, it is in the first preamp tube circuitry.
     
  6. michael.e

    michael.e Supporting Member

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    Awesome! Thank you for the direction! Will hit it tomorrow!
     

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