5e3 build BUZZ

Discussion in 'Shock Brother's DIY Amps' started by Paul Strat, Mar 13, 2019.

  1. Paul Strat

    Paul Strat Tele-Meister

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    04417DCA-842A-4CA6-8C38-19848D98ACE6.jpeg 597505BE-7F4C-4F65-89D7-A64B85D9AC0F.jpeg 8DE86EE2-0675-4E11-B988-7190F3A4C6DF.jpeg AC855463-EAC0-4D30-9B03-D68F433DBFCB.jpeg 3A6AE8DA-68D4-4259-AE8B-72D57203F441.jpeg 0FBE03B5-B247-401A-99D4-1E5A92FAC516.jpeg 77C0075E-68D8-48BB-914F-EC13BE2F149D.jpeg E268D136-3740-4B4B-ACD5-464FAD31C9AB.jpeg E5A612A9-9D08-447F-9105-3F2F2A9533BA.jpeg Good afternoon everyone,
    Got a 5e3 build with an annoying buzz.
    Tried to eliminate all the usual suspects, swapped tubes, reflowed joints, swapped filter caps, swapped v1 coupling caps.
    Had the standby switch wired in but noticed it took longer than normal to lose sound when it was flipped off.
    I’ve been around in circles with this buzz and hopefully someone can see what I’m obviously overlooking. Adding a few pictures and closeups of the ground points. I have a pretty good video with sound of the buzz but apparently it’s too large to upload.
    Thanks in advance for the help.
     

    Attached Files:

  2. D'tar

    D'tar Tele-Afflicted

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    May not influence your humm but I recommend solder tabs and bolting the safety ground and center taps to the chassis.

    Can we see your v1 and v2 heater wiring?

    DO you know if it is 60hz or 120?

    Is hum present without guitar cable inserted

    Pull v1... still hum

    pull v2.... still hum

    That v4 grid stop resistor looks to be damaged.

    How are your filter caps grounded. I recently had to ground the reservoir cap and screen node with the ct to get rid of a hum. The b+2 was tied to the preamp bus and not liking it.
     
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  3. Paul Strat

    Paul Strat Tele-Meister

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  4. Paul Strat

    Paul Strat Tele-Meister

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    Pulling either v1 or v2 kills it
    First two Filter caps are grounded with the center taps on a dedicated bolt next to the PT. Preamp filter cap is on the ground buss. Hum is only present with a guitar plugged in. Forgot to add that. Tried two guitars and different cables.
     
    Last edited: Mar 14, 2019 at 10:26 AM
  5. Paul Strat

    Paul Strat Tele-Meister

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    2AFD3D3B-D440-49D6-8E8E-C34AB3A4CCD6.jpeg
     
  6. Paul Strat

    Paul Strat Tele-Meister

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    The black v1 heater was going around the socket. Just moved it to see if getting it away From the other leads made any difference.
     
  7. Paul Strat

    Paul Strat Tele-Meister

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    Just realized I forgot to add voltage readings

    V5

    Pin

    2/8 5.3

    4/6 373


    V4

    2/7 6.7

    3 361

    4 339

    5/6 fluctuates between 5-50 mv

    8 22.1


    V3

    2/7 6.7

    3 362

    4 339

    5/6 fluctuates between 40-100 mv

    8 22.1


    V2

    1 167

    2 0

    3 1.2

    4/5 6.7

    6 204

    7 17

    8 45


    V1

    1 128

    2 0

    3 1.9

    4/5 6.7

    6 127

    7 0

    8 1.9

    9 6.7
     
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  8. Paul Strat

    Paul Strat Tele-Meister

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    Played around with the heater center tap.
    Tried elevating and an artificial tap with 100 ohm resistors. No noticeable difference in hum.
    Additionally, when plugged into the normal channel, grounding v1 pin 2 lowers the volume and intensity of the buzz, to a moderate hum. but introduces some static noise like a radio not tuned to a station.
    Likewise on pin 7 when plugged into the bright channel.
    If my plasma tv is on it intensifies the buzz.
    Grounding a clip lead and touching all ground points has no effect.
    Chopsticking has no effect.
     
    Last edited: Mar 14, 2019 at 2:45 PM
  9. Syrinx

    Syrinx Tele-Meister

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    for me first thing to check is outlet it is plugged into. I had a build that sounded great at first and then when I took it to test with a guitar it was horrible buzz-was dropped ground on the outlet.
     
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  10. Paul Strat

    Paul Strat Tele-Meister

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    I thought that could be it, but I tried it in a couple more outlets and it’s plugged into a power strip that indicates it’s grounded.
     
  11. 82LesPaul

    82LesPaul TDPRI Member

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    Looking at your pictures in post #1 it appears the lead from the 1M resistor on your input jack could be touching your guitar cable plug?
     
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  12. dan40

    dan40 Tele-Afflicted Silver Supporter

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    Any unusual lighting fixtures over your work bench? Certain types of lights can cause noise, especially in an open and unshielded chassis.
     
  13. Paul Strat

    Paul Strat Tele-Meister

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    I have a couple of led lights, but turning them off doesn’t change anything.
     
  14. Cgci

    Cgci TDPRI Member

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    My recent build has 120hertz hum. I was instructed to add an extra filter cap coming off my rectifier and going straight to ground.
    I’ve yet to try it as I lack an extra cap at the moment.
     
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  15. Uncle Daddy

    Uncle Daddy Tele-Holic

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    Check the contacts on the input jacks. I once got caught with one that was making a partial connection.
     
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  16. ecoast

    ecoast Tele-Holic

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    dimmers in the house?

    move to another outlet?
     
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  17. DADGAD

    DADGAD Tele-Afflicted

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    It looks like you opted for a ground buss along the edge of the board instead of a brass plate, circuit grounding scheme like the original design. I'd revisit that by checking all your grounds. Is the ground buss connected to somewhere on the chassis besides the input jack?

    Where is the output tube cathode resistor grounded?

    Here is a pic of the brass plate from my build.

    [​IMG]
     
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  18. Paul Strat

    Paul Strat Tele-Meister

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    I thought the problem could be there. Replaced all four with no change.
     
  19. Paul Strat

    Paul Strat Tele-Meister

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    No dimmers
    Tried another outlet also
     
  20. King Fan

    King Fan Friend of Leo's Ad Free Member

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    Buzz threads are tricky because buzz has 100 causes. 99% of our helpful guesses will be wrong.

    The video will help — is that 120? Uncle Doug has a video where you can compare yours to 60 and 120...

    I’m waiting for brainiac @D'tar to remind us what it means that pulling V1 and 2 kills the buzz. Does it mean the buzz is in the preamp?

    In your 2nd photo it does look like the guitar plug fails to completely open the shorting jack, as mentioned by Uncle Daddy above. Could be parallax, but it’s a common problem.

    What is the construction and connection of your preamp ground bus? The pics of the top right end make the last link to the chassis look, um, odd. Almost every modern build runs a single wire to the ground lug on an input jack.

    Many buzz issues turn out to be dry or dull solder joints. Have you tried firm chopsticking at each joint? I’d probably reflow any that don’t look wet, clean, and shiny.


    Sent from my iPad using Tapatalk
     
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