MB 4210 - funny noise

Discussion in 'Marshall Amps' started by 5939, Aug 19, 2008.

  1. 5939

    5939 New Member

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    Recently bought an MB4210 - really good bass amp with a lot of bottom end and sweet punch. But there is a strange sound when pumping up the volume a bit through the classic channel - sort og thin, glassy, metallic clanging sound, increased by tapping on the front panel!

    Anyone with the same problem?
     
  2. Duffy

    Duffy New Member

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    That amp has the EC83 preamp tube in it.

    Could it be the tube is loose or needing to be replaced? One would think that Marshall would design the cabinet so the tube can be accessed without too much of a problem. You could check the tube. Tap it with a pencil to see if it is microphonic, but, of course, be aware of all safety precautions that apply to working around tube circuits because lethal power is present even with the amp turned off.

    I think the tube works on the classic channel and your problem seems to be associated with the classic channel. Maybe there is a tube retainer that is loose, or maybe the panel is buzzing because of the overdrive vibrations. Something metallic might be loose in there and vibrating. It might be worth looking at or taking to a tech to have it looked at.

    It's probably something simple like something vibrating or rattling.

    Sounds like a great amp. I have the MB30, thirty watt practice amp and it does not have a tube, but the noise could be something else, since you are pushing a lot of vibrations with those speakers. Loose stuff, or misaligned things like grills or baffles, might make noise. Could be an easy fix.

    Try pressing on the panel from the outside first and pressing on the grill up by the panel from the outside as well. Maybe even push a long nail or something thru the grill from the front and push on the speaker mounting board near the noise in the panel, staying well, well clear of any speaker part. See if you can diminish the noise from the outside before going inside. And since it's still under warranty, maybe just take it to an authorized tech. I'm sure that amp is field servicable.

    Duffy
    Winfield, Pa.
     
  3. steelhorse

    steelhorse New Member

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    Definitely sounds like a pre-amp tube.
     
  4. 5939

    5939 New Member

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    Thanks for your good advice - a managable problem and I shall try not to be electrocuted...
     
  5. mercuryl

    mercuryl New Member

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    Yep. I had / have the same problem. I purchased a 2 year old MB4210 in good cosmetic condition which I have taken to band practice about half a dozen times since purchase.

    It started out with a rattle sound (just like you described) and, last week, in the middle of a jam, the classic channel started making buzzing sounds and lost power. Switching to the clean channel, all was fine.

    So, I guess the pre-amp valve has virtually gone. Will be buying a new one and slotting it in there shortly.
     

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