Super 100jh Buzzing

Discussion in 'The Workbench' started by DearestCreature, Feb 9, 2019.

  1. DearestCreature

    DearestCreature Member

    Joined:
    Jan 16, 2019
    Messages:
    19
    Likes Received:
    26
    Hi guys, I was wondering if I could get some help / advise.

    I'm not really knowledgable about amplifiers at all (apart from what sounds I like!) so please bare with me as i'm sure the aficionados might facepalm. haha :)

    I recently fired up my Super 100JH for the first time since getting it. (sounds great by the way, prefer it to the 1959HW). But there is a buzzing that occurs when the amp is on.
    This doesn't happen when the amp is on standby, only when the amp is fully on.
    So my question is, is that normal?
    It's definitely not a hissing noise or a hum. Just a straight up buzz.

    It does it when there isn't a guitar cable connected to it either so it's not the cable or guitar.
    I don't remember experiencing buzzing with other plexi reissues i've had. although the buzzing does increase and decrease when adjusting the presence which is something I have experienced with similar amps.
    If it's normal then it doesn't bother me but I just want to make sure that the amplifier is functioning properly.

    Apologies in advance if this is a "stupid" question but I guess this forum is the best place to gain knowledge about this kind of stuff. :)
     
  2. jon1917

    jon1917 Active Member

    Joined:
    Feb 20, 2012
    Messages:
    118
    Likes Received:
    56
    Location:
    Ireland
    Start by cleaning all the jack sockets with a good cleaner, including the speaker jacks. Then start by replacing the preamp valves one at a time. If you dont have any spares to hand, try swapping the positions. Guessing the amp is second hand so it can be common that the amp was shipped with worn out valves. Come back if buzz is still there.
     
    DearestCreature likes this.
  3. DearestCreature

    DearestCreature Member

    Joined:
    Jan 16, 2019
    Messages:
    19
    Likes Received:
    26
    Thanks, I'll give it a go tomorrow and report back!
     
  4. neikeel

    neikeel Well-Known Member

    Joined:
    Feb 12, 2014
    Messages:
    3,276
    Likes Received:
    1,723
    Any more on this?
    There are so many things on a ‘used’ amp that has been on unknown tech/non tech persons hands so some pics of what you have got would be invaluable before any serious offers of trouble shooting.
     
  5. DearestCreature

    DearestCreature Member

    Joined:
    Jan 16, 2019
    Messages:
    19
    Likes Received:
    26
    Yep, it's still buzzing, Marshall told me that there will always be small amounts of noise anyway but they said that if i'm unsure they'll have a look at it and service it if can bring it to them. So i'm just going to leave it for a while and take it to Marshall to get serviced when I can arrange to be driven there :)

    Thanks for the replies though, appreciate it, I would take it out of the cabinet and take some pics but i've never done that before and feel a bit uneasy about doing so.
     
  6. ampmadscientist

    ampmadscientist Well-Known Member

    Joined:
    Jun 26, 2014
    Messages:
    12,741
    Likes Received:
    6,628
    Location:
    Left Coast
    It's filament buzz.

    Filament buzz is caused by V1 V2 grids picking up an AC magnetic field from the heater wires which supply V1,V2.

    If the grid wire is closely crossed by the filament wire, or if the grid and filament wires are parallel, there will be buzzing.

    The best strategy is to separate grid wires (pins 2 and 7) from filament wires pins 4/5 and 9.
    The wires pins 2 and 7 should be separated from filament wires 4/5 and 9 as far as possible.

    Or
    if you look at it another way, the filament can run vertical, away from the socket.
    The grid can run horizontal close to the chassis.
    (fender method)

    Or the filament wires can be moved to a different position.
     
    Last edited: Feb 12, 2019
  7. ampmadscientist

    ampmadscientist Well-Known Member

    Joined:
    Jun 26, 2014
    Messages:
    12,741
    Likes Received:
    6,628
    Location:
    Left Coast

    Take out V1 V2 preamp tubes, the buzz should stop. (does it stop?)

    Put in V2, some buzz should come back.
    Put in V1 V2 it will all come back.

    1. Put in V2, turn master volume (if there is one) to 10.
    Listen to buzz and adjust position of V2 filament wires pin 4/5 and 9 wires to minimize buzz. Lock the wires in this position.

    2. Put in V1. turn gain to 10 Listen to buzzing. Adjust position of filament wires on the V1 socket as above.
    Lock down the wires when you have the buzz minimized.
     
  8. neikeel

    neikeel Well-Known Member

    Joined:
    Feb 12, 2014
    Messages:
    3,276
    Likes Received:
    1,723
    He is not going to take the chassis out for pictures so I imagine chopsticking plate and gridwires or redoing the heater wires is likely out of the question, so I guess we will never know in this instance.
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice