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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    Ground buss is only connected to the input jack.
    Cathode resistor and first two filter caps are grounded to bolt next to PT.
     
  2. Paul Strat

    Paul Strat Tele-Meister

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    I listened the Uncle Doug comparison. I’m thinking 60. I’ve chopsticked and reflowed every connection. The ground buss starts at the third filter cap and connects to the normal channel hi input jack.
     
  3. King Fan

    King Fan Friend of Leo's Ad Free Member

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    Ok I see it now, the ground wire goes out of focus.

    I guess I was wondering about this joint... photo makes it look like it’s sitting on the board.

    [​IMG]

    Just trying to locate the issue, not being critical. Oh and I’d double check the resistance readings to chassis on a guitar cable, tip and sleeve, plugged into each jack.


    Sent from my iPad using Tapatalk
     
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  4. Paul Strat

    Paul Strat Tele-Meister

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    Definitely didn’t take it as being critical.
    Appreciate every reply very much.
    Resistance on a cable is right at 1 meg on the high jacks and 136 k on the low jacks.
     
  5. jimgchord

    jimgchord Tele-Holic

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    Are the pots grounded?
     
  6. Paul Strat

    Paul Strat Tele-Meister

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    Both volume pots are grounded to the buss. Tone pot has a .0047 cap to the buss.
     
  7. jimgchord

    jimgchord Tele-Holic

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    Are the pots isolated from the chassis?
     
  8. schmee

    schmee Poster Extraordinaire

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    I built a 5E3 once and decided I would ground everything with a solid copper wire along the pots near the end of the board at the power transformer end. What could go wrong? Well, don't do that. It buzzed. Ground all the input jacks and preamp end of the board near the jacks! Separate the power transformer end etc and ground that on the transformer bolts. Buzz gone when I did that.
     
  9. Paul Strat

    Paul Strat Tele-Meister

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    Mine is split like that.
     
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  10. 82LesPaul

    82LesPaul TDPRI Member

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    Just a reach, but you mentioned you tried 2 guitars. Were they single coil pickup guitars? Did you try a humbucker equipped guitar. Some single coils can be very noisy through a tube amp.
     
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  11. Paul Strat

    Paul Strat Tele-Meister

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    They aren’t isolated. I’ve often wondered about that but it seems common on most layouts I’ve seen to ground the ground lug to the buss.
     
  12. jimgchord

    jimgchord Tele-Holic

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    Probably not your issue. I was just looking for clarification.
     
    Last edited: Mar 15, 2019
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  13. PaceAmps

    PaceAmps TDPRI Member Vendor Member

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    My 73 Strat was a real hummer
     
    Last edited: Mar 15, 2019
  14. D'tar

    D'tar Friend of Leo's

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    Usually amp noise is evaluated without anything plugged in. If it is only when something is plugged in I would suspect that you are injecting noise into the signal path. Does the noise change when touching the strings or moving around with the guitar. does it do it on all the inputs? Sounds like the volume may be pretty high. Cathode bias, no NFB and high volume level can make for quite a bit of noise. You might try another tube in V1 also. I would check over all the input jacks to ensure they are shunting to ground when nothing is plugged in and that your grid leak and grid stop values are correct for each input. Rob has a nice breakdown of the inputs here and some additional troubleshooting info...

    https://robrobinette.com/How_Fender_Input_Jacks_Work.htm

    https://robrobinette.com/Tube_Guitar_Amp_Troubleshooting.htm#Hum_and_Buzz


    IMO this is possibly the hardest thing to troubleshoot over the WWW.
     
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  15. 82LesPaul

    82LesPaul TDPRI Member

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    This problem is a tough one. I know this is basic, but I got this from Rob's website and performed it on all my input and speaker jacks before power up.

    Before adding power to a new amp be sure and verify the safety ground connection. Plug a guitar cable into an input jack and check that you have continuity (meter "beep") between the guitar cable's sleeve (the part that isn't the tip) and the amp's power cord ground prong.

    If your amp has a main speaker jack, plug a cable in and test again for continuity between the cable sleeve and power cord ground prong. If your amp has speaker wires one of them should show continuity with the power cord ground prong.

    After that I would start continuity between all ground points in the schematic and chassis.
     
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  16. 82LesPaul

    82LesPaul TDPRI Member

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    If you could post some additional pictures of your three prong power cord wiring that may help. I recall earlier you mentioned removing the standby. In your original post it appears odd that the green power cord ground wire is coming out of the sheathing below the hot and neutral wires.
     
  17. Paul Strat

    Paul Strat Tele-Meister

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    I agree on the difficulty in trying to diagnose. I’ve been what seems like around the world with this one and can’t seem to find anything out of the way other than fluctuating current on the output tube grids.
    I initially had the inputs wired like Rob’s Bassman layout. I changed out all four and wired them like his updated 5e3 layout.
    The amp is silent with nothing plugged in except for a little hiss at max volume. The buzz is slight from about 5 on the volume control and what is heard in the video is at max volume. Moving away from the amp doesn’t really change it like it normally would. It drops in volume in the low input jacks but is still noticeable. Both high jacks sound about the same.
     
  18. Paul Strat

    Paul Strat Tele-Meister

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    422900D3-2736-4F80-A62E-4012ED838190.jpeg 1EC9C0B1-EED7-49FF-9001-FACBB4F17437.jpeg
    Power cord wiring is from the Mojotone layout without a ground or standby switch.
     
  19. Paul Strat

    Paul Strat Tele-Meister

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    The green wire is going to a solder lug.
     
  20. PaceAmps

    PaceAmps TDPRI Member Vendor Member

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    .
     
    Last edited: Mar 15, 2019
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