Nasty hum in my '74 V4B

Discussion in 'Amps and Cabs [BG]' started by MichelD, Apr 17, 2019.


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  1. Sunnampeg

    Sunnampeg

    Nov 11, 2019
    UK
    yes
     
  2. Sunnampeg

    Sunnampeg

    Nov 11, 2019
    UK
    in fact, when he s hackery proposal seems weird to me also, and i do not like the idea.but after all this story I understand he does not want to go deep into the problem, he has experience but probably not a lot with vintage Ampeg's, but still, I do not understand why he does not want to find the problem.I think I should bring my amp to someone else.what do you think
     
    pcake likes this.
  3. MichelD

    MichelD

    May 19, 2014
    Yes
     
  4. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    Yes, he has not identified the root cause of your problem.

    You need to find a really qualified service guy who is EXPERIENCED in this Ampeg model. It's not that difficult for a pro.
     
    BassmanPaul and bobyoung53 like this.
  5. Sunnampeg

    Sunnampeg

    Nov 11, 2019
    UK
    You are definitely right, I ve received a call this morning from him and he said that there is also another problem the output tubes are too red, they are sucking too much electricity also, he said he needs to remake the bias and change some components..and that there is a possibility that the whole output tube set goes off during the test.but as soon as he has done I will let it check to someone else.
     
  6. Sunnampeg

    Sunnampeg

    Nov 11, 2019
    UK
    you are definitely right, If you are a professional it should not be a problem , but here in UK London techs rarely see vintage v4b.
     
  7. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    It's a fairly conventional amp, not that difficult to repair.
     
    BassmanPaul likes this.
  8. Sunnampeg

    Sunnampeg

    Nov 11, 2019
    UK
    ok so definitely I ve to take it away from his hands before it does damage. As someone of you have said previously( I 've seen a lot of fails by a bad repair).he s basically trying to fix the amp by attempts, considering each fault itself instead of watching the big picture and arrive at the source.
     
  9. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    I used to teach systematic, structured troubleshooting to techs.

    Some folks just don't have the thought processes necessary to make a good tech, these are the guys who shouldn't be working on your amps IME.
     
    Sunnampeg likes this.
  10. Sunnampeg

    Sunnampeg

    Nov 11, 2019
    UK
    i guess how this guy is arrived 66yrs old doing this job
    ...i satart to be scared
     
  11. BassmanPaul

    BassmanPaul Inactive

    If I ever get to meet you I'll bring you an apple. :D
     
    agedhorse and Sunnampeg like this.
  12. Sunnampeg

    Sunnampeg

    Nov 11, 2019
    UK
    20200612_220300[1].jpg
     
  13. Sunnampeg

    Sunnampeg

    Nov 11, 2019
    UK
     
  14. BassmanPaul

    BassmanPaul Inactive

    With the red glow on the plates the tubes are not happy. You need to set the bias more negative to stop this. I suspect this is where your hum comes from.
     
  15. Sunnampeg

    Sunnampeg

    Nov 11, 2019
    UK
    mmm so its too red because to me it does not look red...so definitely it needs to go back to another tech.soon, i don t understand why this guy doesn't want to fix my amp.***...
    thank you all guys speak you at the next TECH-------
     
  16. Sunnampeg

    Sunnampeg

    Nov 11, 2019
    UK
    the new tech finally individuates the higher bias and after lower, it was still humming too much for me. he said that the amp was not humming too much, but for my tastes yes so he came out with the swap od the 12dw7 with ecc81, now the hum is almost zero but apparently I 've lost a bit of gain, I hope does not affect the output and the bright and growly tone of the v4b, he said that is very easy to put back the circuit with 12dw7 with zero risks of damage..let s hope I like it
     
    beans-on-toast likes this.
  17. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    That's a good compromise IMO.
     
    Sunnampeg likes this.
  18. Sunnampeg

    Sunnampeg

    Nov 11, 2019
    UK
    Yes if it does not change the aggressive bright tone of the amp I m happy to keep it but what should I expect from this change preamp tube in terms of tone he said I will have less gain..I m not able to figure it out.. I mean is 100w if is not going to be tonally aggressive, nobody is going to hear me with my band. my guitar player has mesa and a gibson flyng v
     
  19. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    You can use a pedal if you want more distortion. Perhaps use a treble booster to push the input into saturation. Add a second speaker cabinet if it isn’t loud enough.
     
  20. Sunnampeg

    Sunnampeg

    Nov 11, 2019
    UK
    I don't like use pedal and I cant carry 2 cab even if i would like it
     
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