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Thunderfunk TFB420 hums really loud.

Discussion in 'Amps and Cabs [BG]' started by Lowtonejoe, Mar 20, 2005.

  1. Lowtonejoe

    Lowtonejoe Supporting Member

    Jul 3, 2004
    Pasco, WA
    I just bought a Thunderfunk TFB420 from a very reputable dealer who sells used equipment. I have not had a chance to talk to them about this since I just got my amp today (the first really excellent service I have ever had from Fed Ex Home Delivery!) and they will not be open again until Monday.

    This is a used amp. It looks to be in really great condition.

    But dang! This sucker hums like crazy! Not like it's in the preamp or amp. There is an immediate hum on power up then you hear the speakers come in with the same hum at a lesser volume.

    If you turn the amp up the hum does not get louder. It definitely sounds like a component isssue.

    The amp sounds great by the way. One of the best plug-and-play tones I have ever heard. My only concern with the amp is this hum.

    I have heard contactors hum like this at work but I am pretty sure there are no contactors on the amp...but I could be wrong I guess. Maybe a relay anyway. OR a transformer.

    I A/B'd it against my GK700RBII and my Rack (RBI + PLX2402) and it is significantly louder than either of them.

    Anyone else run into this kind of problem? Is it common? Is it O.K.?

    Any help would be appreciated.



  2. boobinga


    Feb 9, 2001
    Pacific NW
    Sorry I can't define the cause of the hum. If it were mine, I'd be contacting the dealer on Monday for help. The Thunderfunk is a great amp and should not hum at all.
  3. David Wilson

    David Wilson Supporting Member

    Oct 14, 2002
    Lower Westchester, NY
    No, I've never had any hum with mine. Definitely not normal.
  4. My new tfb550 hums too, but very silently, one source is transformer (I have 240V switched on the back panel), another noise comes from my cabinet (Accugroove Tri210L, no instrument plugged in, gain and volume at zero). It is not a problem, it is very very silent, but I dont know if it is normal - other owners report absolutely silent operation... ?
  5. alibloke


    Dec 17, 2004
    Bristol, England
    I had an almost identical problem on my old Trace Elliot rig, though I never found out what it was. Trace told me this was 'normal'!! :mad: Needless to say that it was the last Trace product I ever bought.
    Anyhow I'm getting off topic! ;)

    Various engineers had theories ranging from ground loops inside the amp, all the way to some sort of 'fan' related hum. If you do manage to track down what is causing your hum, please let me know as I'd be very interested to hear of the cause!
  6. Sounds like a power supply issue...?
  7. jobu3

    jobu3 It ain’t ideal but I deal Supporting Member

    Feb 17, 2002
    Mountain Top, PA
    My 20 year old BH-420 is dead quiet.

    I'd try a different outlet in the house or even try a different building if possible. Certain amps act differently on dirty AC while others can seemingly handle it without flinching.
  8. Lowtonejoe

    Lowtonejoe Supporting Member

    Jul 3, 2004
    Pasco, WA

    The humming is coming mostly from 3 of 4 blue capacitors inside the amp. Nothing from the transformer and nothing from the two black capacitors.

    Is this o.k.? The danged thing sounds great but I am very disappointed about the hum, my plan was to use it to record through a miked cabinet.

    The amp was made 11/03 so I suppose something could be getting tired.


    Maybe I'll call Thunderfunk tomorrow.


  9. Joe P

    Joe P

    Jul 15, 2004
    Milwaukee, WI
    That's what I'm thinking - a bad power supply cap.

    Maybe it has two or three electrolytics per rail, and only one is bad, or has an open lead (if all the resevoiur capacitance for a rail was open, I'd think that it would make a horrendous hum, and probably not be capable of putting through a normal, clean bass sound).

  10. KB


    Jan 13, 2000
    Chapel Hill, NC
    My TFB550 is mostly dead quiet (there is a very very faint hum if I put my ear right up to it, probably coming from the transformer...but basically it is quiet.). I contact Dave Funk and get his thoughts. He could probably do a quick repair for you. He reads talkbass so you may even get a comment from him here.
  11. I'd call Dave...
    If someone can help you - it's him!
  12. mgmadian


    Feb 4, 2002
    Austin, TX
    I'd be interested in hearing what you learn about the hum from Dave/Thunderfunk. Ditto that Dave's very helpful and offers strong support. But good luck tryin' to call... I never managed to dig up a phone number and he didn't seem too excited about givin' one out. But like I said, good support still available by email (albeit sometimes brief, and I'd still encourage him to make a phone number available to people using Thunderfunk equipment... ;)) Great-sounding amp.
  13. jerry

    jerry Too old for a hiptrip Gold Supporting Member

    Dec 13, 1999
    I've had mine for almost two years, and it's one of the older models, mine's dead silent.
  14. Joe BassPlayer

    Joe BassPlayer Supporting Member

    Aug 18, 2002
    I purchased a new SWR Basic Black several years ago that exibited the same problem. I took the amp chassis out and examined the PCB. It turned out to be the electrolytic cap that filtered the A/C . After a close inspection someone bent one of the cap leads too close to the cap body and it broke away from the case. I replaced it and the problem was solved. As others have stated, call Dave. He'd be able to ID the A/C filtering cap on the board. If that doesn't work (or you're not comfortable doing some basic trouble shooting), contact the music store that you purchased it from and arrange to have it serviced at a service center convienient to you.
    And you're right, the Thunderfunk Rocks! :bassist:
  15. Lowtonejoe

    Lowtonejoe Supporting Member

    Jul 3, 2004
    Pasco, WA
    Thanks for all the replies guy!

    I have been in touch with Dave via e-mail.

    Except for the shipping costs he is willing to fix it for free (he too thinks it's a cap issue).

    If you ask me it is a small price to pay for this great sounding amp.

    I appreciate Dave's willingness to take care of this in such a noble manner. He sure doesn't have to but he is.



  16. David Wilson

    David Wilson Supporting Member

    Oct 14, 2002
    Lower Westchester, NY
    Yeah, I had a slight issue with mine and Dave was a great help.
    I had an intermittent distortion issue which was hard to replicate, rather than saying "I don't hear anything wrong", Dave sent me a new amp on receipt of the old one.
  17. Lowtonejoe

    Lowtonejoe Supporting Member

    Jul 3, 2004
    Pasco, WA
    I got this amp back from Dave about a week ago.


    It's quiet now! And it sounds awesome!

    I spent some time A/B'ing it against my rack (Sansamp RBI/QSC PLX2402) and my GK 700RBII.

    It does them both!

    This thing is totally awesome. I can get a thick, warm sound and I can get a punchy, bright sound just by using the enhance and timbre knobs!

    I also experimented with the eq. It's semi-parametric and very, very useable. It's a tweakers playground! I can't imagine a mix that this thing couldn't cut through and still sound great!

    This amp rocks!

    Dave's service was awesome!

    Yes, I like this amp.


  18. mgmadian


    Feb 4, 2002
    Austin, TX
    Awesome... always good to see service like that. Dave is indeed among the best.
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