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Ground pilot light? 5e3 build

Discussion in 'Amp Central Station' started by deathcap, Jan 23, 2021.

  1. Jan 23, 2021 #1
    deathcap

    deathcap TDPRI Member

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    Still searching for this ground hum issue on a diy build.
    secondary has no center tap for the 6.3v heater filaments so I put an artificial CT on V1 and not on the pilot light.

    [​IMG]

    there are insulators between the wings and the base on the pilot light so the bulb base never touches the bracket holding it and never touches the chassis to ground. I scavenged the pilot light and can not remember what it came from. I can attach a clip to the lower wing that makes contact with the bulb base and the chassis as shown below, and the hum goes away. Can some one take a look at theirs and help me figure out what's going on here?

    [​IMG]
     
    Last edited: Jan 23, 2021
  2. Jan 23, 2021 #2
    Boreas

    Boreas Friend of Leo's Silver Supporter

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    Does the bulb light properly? Close-up pix of the socket connections?
     
  3. Jan 23, 2021 #3
    King Fan

    King Fan Poster Extraordinaire Ad Free Member

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    What do those artificial CT resistors connect to? Preamp ground? At any rate it’s an awkward reach. Have you tried them to a solder lug on a nearby socket bolt? Or near the lamp? Your clip test suggests your artificial CT is bad in some way...

    Also I can’t quite read the color codes on those resistors.
     
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  4. Jan 23, 2021 #4
    D'tar

    D'tar Friend of Leo's

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    What value resistor are you using for the artificial tap? I cant see the band colors clearly but the multiplier band suggest something in the 10k + range. You should be using 100 ohm resistors. Brown black brown.
     
  5. Jan 23, 2021 #5
    deathcap

    deathcap TDPRI Member

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    V1
    [​IMG]

    V2
    [​IMG]

    Power tubes
    [​IMG]

    Rectifier
    [​IMG]

    Pilot
    [​IMG]


    Artificial CT resistors to chassis ground are 100K 1W
     
  6. Jan 23, 2021 #6
    King Fan

    King Fan Poster Extraordinaire Ad Free Member

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    Yes, and as @D'tar noted they should be 100R. R≠K. :)

    While we're at it, did you tell us what they're connected to? Is it the preamp ground?
     
  7. Jan 23, 2021 #7
    deathcap

    deathcap TDPRI Member

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    shoot, connected to pin 9 and the 4-5 pins heater wires on the preamp tube.
     
  8. Jan 23, 2021 #8
    deathcap

    deathcap TDPRI Member

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    the artificial CT location was temporary until I could figure out the hum. so now I know.
     
  9. Jan 23, 2021 #9
    deathcap

    deathcap TDPRI Member

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    Thank you
     
  10. Jan 23, 2021 #10
    King Fan

    King Fan Poster Extraordinaire Ad Free Member

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    Sorry, I assumed that. I meant the other end. But... if temporary, it won't matter now. Let us know what you end up doing.
     
  11. Jan 23, 2021 #11
    deathcap

    deathcap TDPRI Member

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    the other end? the PT doesn't have a CT. I don't understand. The filaments come out of the PT and connect to the pilot, then it goes to the first power tube and continues down.
     
  12. Jan 23, 2021 #12
    King Fan

    King Fan Poster Extraordinaire Ad Free Member

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    NVM, let us know how it ends up and if it fixes your hum. :)
     
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  13. Jan 23, 2021 #13
    deathcap

    deathcap TDPRI Member

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    the other end of the resistors are connected to a bolt on the chassis. thanks again
     
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