Bugera v5 hum !

Discussion in 'Glowing Bottle Tube Amp Forum' started by Topdude, Sep 22, 2017.

  1. Topdude

    Topdude TDPRI Member

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    Hi, just signed up and have a question about mains hum on my Bugera v5.
    I have read through the massive Bugera club thread and am in the process of trying the recommended bright mods and valve / tube swaps.
    My amp has the often mentioned mains hum, most noticeable on the 5w setting and least on the 0.1w setting. Although this has been mentioned by several people I have not seen anyone suggest a remedy ?
    I came across the Rat mod site where they say it can be fixed but of course they don't give any further information.
    Considering the wealth of excellent info on tweeking the sound there must be something somewhere about curing the hum ?
    Any thoughts gratefully received.
    Thanks Terry.
     
  2. Silverface

    Silverface Poster Extraordinaire Ad Free Member

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    First questions:

    Have you checked your AC power source with an outlet tester ($60 at most hardware stores) to verify your outlet(s) are wired and grounded correctly? If not you should do this asap so you're not "hum chasing" over a problem that has nothing to do with the amp.

    Is it the same with 1) single coil pickups, 2) humbuckings, 3) nothing plugged in, and/or is the guitar (if one is plugged in) near and/or facing the amp?

    Is the amp plugged into the same outlet/extension as ....or are the amp or guitar anywhere near...TV, computer, monitor, AV equipment, appliances of any kind?

    Are there fluorescent lights - including the small, "twisty" replacement bulbs - on the same circuit or in the same room?

    Have you swapped power tubes? Single-ended amps inherently have *some* hum - there's NO avoiding it - and EL84's tend to be a bit more problematic than 6V6's.

    Are you hearing hum with NO pedals? What type of cable?

    It would help quite a bit if you posted a soundfile of the amp at idle and played clean. It hasn't been uncommon for small amp owners to do so and discover the hum is completely normal.

    If you are set up any of the ways outlined above try changing things around (after verifying the outlet). "Environmental" hm inducers are actually the most common.

    Last - it's not a great idea to mod anything in an amp that may have issues. Mods can exponentially complicate issues, especially because of lead dress issues. You should always fix (or eliminate the cause of) problems first.

    Hope that helps!
     
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  3. Dacious

    Dacious Poster Extraordinaire

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    Thought about teaching it the words? :lol:

    Sorry had to get in before anyone else..
     
  4. Topdude

    Topdude TDPRI Member

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    Ok, thanks for the two replies, well the first one anyway !!

    Spent some time checking things over the weekend -
    Nothing to do with mains power, florescent lights or other electrical appliances.
    Nothing to do with the guitar or cable.
    The amp starts to hum after the valves have warmed up with no guitar plugged in.
    Replaced both valves but made no difference. It is not a mechanical hum from the transformer but definitely amplified through the circuit.
    As said before it is fairly loud on the 5w setting but almost silent on the 0.1w setting. Unfortunately the 5w setting is the one recommended for best tone.
    Also other v5 owners have mentioned the same hum on their amp.
    So my question really is with all the work people have done regarding tone mods there must be something that can be done to silence the mains hum ?
    Thanks Terry.
     
  5. Topdude

    Topdude TDPRI Member

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    Ok, just to answer my own question in case it helps someone else.
    After some digging around I found the v5 is based on the Epiphone Valve Junior and there is a LOT of modding information on that amp. Some of which is incorporated in the v5 already like DC supply to the valve heaters, and a few other noise reduction ideas which I will look into.
     
  6. VintageSG

    VintageSG Friend of Leo's Ad Free Member

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    What Silverface put sums it up really. I have owned a few single ended amps and they have all had some detectable hum. I have wasted shop owners time trying out amps, and all the single ended amps have hummed. Some worse than others.
    The worst offenders were all single 12AX7 + single EL84.
    Next on the scale of quietness came amps with more than one 12AX7 + single EL84, plus single 12AX7 + one 6V6. They're about equal. It's only when the money spent ramps right up do you start to get really quiet single ended amps. Or, build one yourself.
    There's a lot of stuff in the V5, a lot going off in a small space. There will be noise. Providing that noise doesn't interfere when playing, try and live with it. If it really grates, get shot of it and buy a push-pull amp.
     
  7. Fenderman803

    Fenderman803 TDPRI Member

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    Mine has an ever so slight hum on the 5 watt setting, nothing that's to the point of annoying, and not even noticeable on the 1 or 01 setting and from most threads is pretty common.
    There is a thread sorry I don't remember which where the dude that used to do the complete Rat Mods for this amp, but doesn't anymore posted like every thing he did to the V5. Probably if you Goggle Bugera V5 Rat Mod you'd be able to find the post.
     
  8. johnnymg

    johnnymg TDPRI Member

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    Does anyone have a link (or explanation) to the hum fix for the V5/T5 amp?
     
  9. RegularJim

    RegularJim TDPRI Member

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    Sorry to resurrect an old post, but I was wondering if you ever found a fix for the 5 watt hum issue.
     
  10. Topdude

    Topdude TDPRI Member

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    Hi, to answer your question yes I did find a cure for the hum problem. I contacted Andy at Rat Valve Amps and asked what they did to fix it. He kindly sent me a circuit diagram for an extra smoothing stage in the power supply that supplies the power tube.
    I wired up the extra components on a small tag strip and mounted it alongside the main board in the chassis.

    This fixed about 90% of the hum so my v5 is virtually silent now. Bear in mind mine is an original version not an Infinium.

    I would warn anyone that some knowledge of electronics and electrical safety is required to do this !!!

    If you send me your email address I can forward the information to you.
     
  11. johnnymg

    johnnymg TDPRI Member

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    Can you post the info directly here?

    thanks
     
  12. Topdude

    Topdude TDPRI Member

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    Ok, found time to post the diagrams to reduce hum on the V5.

    Circuit diagram for original V5

    v5revcd.jpg





    Circuit diagram for mods to power supply section

    Scan.jpg
    Photo of modded board

    WP_20190610_14_31_23_Pro2.jpg

    The purpose of this mod is to provide extra smoothing for V+ going to the EL84 tube anode
    There is no room on the board for extra components
    I cut the track on the board after the C2+ connection (and fitted a new C2 so the +leg can poke out the back of the board a little)
    Connected a wire from the extended C2+ leg to the new tag strip
    Connected the return wire to X4 (brown wire to output transformer) as this was a convenient place for a good solder connection
    The white ground wire goes to the common ground point on the circuit board
    The tag strip is fitted with insulating spacers to the chassis
    The 220R resistor is mounted directly to the chassis as a heatsink

    This applies to the original V5 and not the Infinium model which may be different !

    The result is much reduced hum on all attenuator settings.

    If you don't fully understand what i have posted please get help from someone who does !!
     
    Last edited: Jun 13, 2019
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  13. Silverface

    Silverface Poster Extraordinaire Ad Free Member

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    The hum reduction would seem to be due to the extra filtration.

    Did you check plate voltages before and after? At first glance it looks like there would be some minor amount of voltage drop from the 220 ohm resistor.
     
  14. johnnymg

    johnnymg TDPRI Member

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    If I do this mod I'll use a smaller (~100 OHM) series res and larger (~100 uF or whatever will fit) cap. IMO, his amp is already too 'weak kneed' to take any extra plate voltage drop.
     
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