trouble with a mint brown super

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by tdh, May 31, 2005.


  1. tdh

    tdh Silver Supporting Member

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    Hi all,
    I'm looking for advice on what to do with this amp.It's a 1960-61 brown super,all orig,in showcase condition.It sounds wonderfull with the cool vibrato etc.
    The problem is that it has a very intermittant crackle,breakup when played.I brought it to a tech that I trust and he has told me that it will only do the "bad noise" with the chassis in the amp and not on the bench.He has said that because all the parts are original that he doesn't feel right about changing bit by bit hoping to isolate the problem.So I have this beautiful amp that can't be trusted!I paid pretty large money for it a few years ago.
    Any thoughts?
    Thanks much,
    Tim DeHuff
     
  2. Swarty

    Swarty Member

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    Sounds like it could be related to vibration caused by the speaker...which may be a bad solder joint (if it were, smacking the chassis/amp should make the noise). Could also be a speaker issue. One thing would be to see if you can get the problem to happen with the chassis partially pulled (slid back a few inches. If so, the tech should be able to isolate the noise with a scope.

    I agree with your tech as far as not changing parts that are not proven bad. Hard to fix a problem that can't be reproduced, but if that tech has thrown in the towel it is time for another tech. That amp is very cool and deserves to be working perfectly.

    Is it possible that it could be something on the cab rattling like a loose baffle screw? Vibrating grill cloth? Speaker nut?
     
  3. RussB

    RussB low rent hobbyist Silver Supporting Member

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    The amp is over 40 years old (you new that) It will require service to be 100%. Original parts will have to be replaced. You must decide if it's a static museum piece, or a usable guitar amplifier.

    You could always consider another tech, someone who is an expert on restoring vintage Fenders (Uncle Spot comes to mind)
     
  4. Richard Guy

    Richard Guy Member

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    TDH,

    Once you have tried the other good suggestions that are posted and you still have issue, does it happen with the first preamp tube removed? If so, replace the 100K resistors in and around the preamp. I would only 'go-in' once you have tried the other suggestions.
     
  5. MojoHand

    MojoHand Supporting Member

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    I agree about being very cautious regarding changing parts in that amp. A piece like that actually rides the line between working amp and museum piece. You want to treat it with a great deal of respect and only change what you absolutely have to change. I agree with Swarty that the problem sounds like it may be vibration related. Crackle is usually caused by a bad connection or failing component. Vibration or heat can trigger the symptom. Try (gently) smacking the amp while playing to see if you can induce the crackle. If so, you can isolate a bad joint/failing component by powering up with the chassis on the bench and probing all connections with chopsticks (this job is a ticket to electrocution, so leave it to the experts). Ask your tech if he did anything like that and if he's considered vibration related problems. Also, he did change all your tubes and clean all your tube sockets, right? Because a crackle can come from a bad tube or tube connection and you want to isolate that first.
     
  6. Wakarusa

    Wakarusa Member

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    Definitely check the tubes first, after that the "half way in" and "smack it around" are good suggestions.

    That said, I've got a minty '62 Super that I don't think twice about replacing aged or misbehaved components. But then I like to play 'em more than I like to look at 'em.
     
  7. markdurham

    markdurham Member

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    If the problem doesn't appear until the amp heats up, it may not get hot enough when removed from the chassis to expose the problem. If so, have your tech use his heat gun to heat up the resistors, one by one, and see if the problem appears. This is a classic troubleshooting technique for vintage Fenders. Start with the resistors around V1, like Richard said.
    Those CC resistors can get a tiny crack across them or can be broken where the lead connects to the body of the resistor, and it's just invisible. Heat from running the amp, or from a heat gun, will cause the resistor and leads to expand (at different rates) and it's then that the problem appears.
    hth,markd
     
  8. bob-i

    bob-i Member

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    Personally I'd find another tech. You shouldn't have to replace parts one at a time to isolate the problem, you should be able to use a heat gun or a freezing spray to help troubleshoot. You can also jiggle and tap parts to try to bring it out.

    There are any number of things that can cause a problem like this.

    Cold solder joints... An amp this old should have the joints reflowed anyway

    loose or corroded tube sockets... tapping and jiggling will help to isolate these issues

    Circuit board shorting on the chassis.... Where I've never seen it I've read that the cardboard under the circuit board can absolb moisture and start conduction.

    Bad filter caps... again these should be replaced, they're 40 years old and were designed to last 10 years.

    Good luck, that's too nice an amp, you should use it!!
     
  9. tdh

    tdh Silver Supporting Member

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    Hi to all,
    I used a tech,Chris Davis in Wappingers Falls that is only home now and then.
    I got lucky and found him home,drove an hour to his house and we both tapped and listened for a good hour or so and finally found a cap, Bypass? that was not making proper contact.He changed it out and I saved the old one.
    She sounds fine now.This is a great resource.I hardly ever post but I'm on every night for the past several years.
    Thanks again for all the replies I've gotten!
    Tim
     
  10. bob-i

    bob-i Member

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    Great news.
     
  11. mad dog

    mad dog Silver Supporting Member

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    tdh: good news about your amp. BTW, that's a cool amp. Played a memorable brown super recently. The best of the browns IMHO, and that's saying something, as the Concert is another all-time favorite.
     
  12. RussB

    RussB low rent hobbyist Silver Supporting Member

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    ...imagine how good it would sound with new filter caps...
     
  13. Blue Strat

    Blue Strat Member

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    ....or how unoriginal the amp will be when the bias cap fails and the power tubes run wide open and take out the OT.

    I've seen this happen too many times in all original amps that sounded great until they blew up.
     

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