Used tube amp maintenance

Discussion in 'Glowing Bottle Tube Amp Forum' started by Wallaby, Feb 6, 2019.

  1. Wallaby

    Wallaby Tele-Meister

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    Hi everybody,

    I have a 2009 Swart STR Tweed that I've decided I'm going to keep. It fits my family room situation really well and it sounds great.

    It has a few issues - the volume pot doesn't sweep smoothly in a couple of spots, for instance ( I've cleaned the pots ), it hums a bit even when the volume is all the way down, etc.

    I am taking it to an area amp doctor that has a good reputation, and I want to know what I should ask him about.

    For instance, the volume pot, is that hum normal, and the 10-year old capacitors are things I know I'm going to mention to him. I also just want the peace of mind of having him looking at it all over to see what might be needed and get issues addressed if needed. I might even mention a low-power mod to see what he thinks.

    I would be grateful for your suggestions and guidance!

    Thanks in advance,

    - John
     
  2. CV Jee Beez

    CV Jee Beez Tele-Holic

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    Best of luck. 10 year old caps should be fine. If filter caps are bad you'll hear a 120 Hz hum. How do you know the hum is attributed to the volume pot? The reason I ask is the hum may have another point of origin.
     
  3. Wallaby

    Wallaby Tele-Meister

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    Hi CV,

    I actually don't know the hum is related to the volume pot, I just wanted to explain that the hum is there even with the volume turned down and with nothing plugged in to the amp.

    WRT the volume pot specifically, I want it replaced, it seems damaged or goobered up. It catches in a couple of places in its travel even after I cleaned it. The other pots are fine.

    One thing I noticed about the hum - the amp can use 6v6 or 6l6 tubes, so naturally I've tried multiples of both... the hum seemed to be louder with a 6l6.

    Maybe that indicates something?

    I appreciate your comment - thanks!
     
  4. schmee

    schmee Poster Extraordinaire

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    It sounds like the pot should be replaced to me for the one issue anyway.
    The hum is hard to know, was it always there? Being an early Swart.... Maybe he had a learning curve. Some of the Fender tweeds are very sensitive to grounding schemes.
    We dont know the life of modern caps really, maybe it is filters...
     
  5. Wallaby

    Wallaby Tele-Meister

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    Thanks Schmee.

    I think this illustrates why I am taking the amp to a professional for a thorough going-over. I am not going to be able to sort it out myself - I just listened to Youtube to figure out what a 120hz hum sounds like, and I *think* that's the sound of the hum I hear.

    Maybe the best course is to tell him what I know, let him I know I want him to do what is needed as if it was his amp, and let him do his thing. Hopefully I can learn something and put it in the databank for next time.
     
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  6. brucerbc

    brucerbc TDPRI Member

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    I've found Swart to be pretty responsive and accommodating when I've had issues with their gear. Have you considered emailing or calling them and asking for advice? If you don't mind shipping the amp, then they may service it for you. For a fee, almost certainly, but they would know the circuit best for what that's worth. Just a thought. Best of luck.
     
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  7. Wally

    Wally Telefied Ad Free Member

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    I have found that cold solder joints on a pot can cause scratchiness. So can a bad tone cap.
     
  8. Wallaby

    Wallaby Tele-Meister

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    I think this is a good idea, and I may do that in the end. I'd like to see what the local person has to say too.



     
  9. Wallaby

    Wallaby Tele-Meister

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    I appreciate that thought, I haven't really looked at the solder joints. To be clear, it is a physical scratch or bump in the pot sweep, not a scratchy sound. You can feel it with your finger tips when you turn it.

     
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  10. Milspec

    Milspec Friend of Leo's

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    Growing up in my family's auto repair shop I have found that you are better off not suggesting anything to the amp tech. No need to ask any more than "how much" or "what would you suggest for improvements"? He is a reputable tech, so trust his skills and advice. I just tell my shop that I want a reliable amp that is up to specs....he does the rest.
     
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  11. Wallaby

    Wallaby Tele-Meister

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    I think troubleshooting my minor issues is turning out to be irresistable, and I apologize for that! You all are putting on your thinking caps and giving me the benefits of your expertise - thank you.

    I'm also looking for advice about how to best to handle visiting the amp repairman. I've never taken an amp in for repair or maintenance, and I've been a little leary based on things I've read and heard about the amp repair experience. I finally found someone with a good reputation, good mentions on internet forums, and importantly is convenient and local to me.

    I'm hoping for a good relationship and good results and would like to end up with a reliable option for these services in the future.
     
  12. Wallaby

    Wallaby Tele-Meister

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    That sounds like good advice, it's what I normally do - sort of an "aces in their places" approach. Trust is important and starts a good relationship more often than not in my experience. Thanks for the advice, Milspec.

     
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  13. LOSTVENTURE

    LOSTVENTURE Tele-Afflicted

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    The less you tell the repairman, the better. Let him listen to the amp and let him tell you what he thinks.
    Second guessing some of the problems that you have mentioned might lead to unnecessary cost.
    If he has a decent reputation then he'll hear any problems and act accordingly.
    That all could lead to the relationship that serves both you and the repair guy best.
    Good luck.
     
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  14. BobbyZ

    BobbyZ Doctor of Teleocity

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    Yeah sometimes it's best to let the repair guy figure it out.
    My chainsaw story from the only time I ever brought a chainsaw in for repairs.
    About 1985 I had an old Pro Mac 55 saw, it'd run fine awhile then die. Based on experience with cars, I assumed it was the condenser. (an electrolytic capacitor) Sometimes they'd heat up and stop working.
    Since I didn't have a puller to get the flywheel off I took it in and told them to do the points and condenser.
    Dammed thing did the same thing afterwards!
    Long story short, the vent on the fuel cap was just plugged.
    If I would've just let them do their thing they probably would've figured it out. :)
     
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  15. clintj

    clintj Friend of Leo's

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    I like details and descriptions when repairs are dropped off, and it's even better if you can show me what it's doing and when it does it. There's often important clues to be found. Sometimes the problem disappears on my bench which suggests the customer has a power issue. I also ask the customer bring as much of the setup as possible. Yes, I have a couple of speaker cabs for testing but if that weird buzz is because you have a bad speaker I'm not going to find it.

    As far as customer suggestions, if I'm not excessively busy or have a rush repair in, I don't mind talking through them. Sometimes they have some validity, sometimes they're way off mark and I can usually explain why, sometimes it's a deeper or multilayer problem that'll take a few rounds of digging to resolve.

    Sent from my Pixel 2 using Tapatalk
     
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  16. Wally

    Wally Telefied Ad Free Member

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    I like the owner/user to be able to give descriptions of the problem. I will also help them understand how to do simple diagnostics themselves....this can help a tech, ime. If an owner/user starts telling me how to do the job, I figure they don’t need me. (;^)
     
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  17. flyswatter

    flyswatter Friend of Leo's

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    +1. I've serviced Swarts, and when I emailed with queries they were always quick and helpful in suggesting things.

    +1 Also on the informed owner who can describe problems without getting their back up when I disagree with their diagnosis.
     
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  18. Wallaby

    Wallaby Tele-Meister

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    This is wonderful, everybody I really appreciate your insights!
     
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  19. Wallaby

    Wallaby Tele-Meister

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    Harkening back to Bobby Z.'s gas cap anecdote and the other excellent advice to contact Swart directly - I took Kelly at Swart's advice and reseated the chicken-head knob attached to the volume pot and made sure there was adequate clearance between the inside of the knob and the nut for the potentiometer.

    The volume pot now turns very smoothly :)

    D'oh!
     
    Wally likes this.
  20. Mike Eskimo

    Mike Eskimo Doctor of Teleocity Ad Free Member

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    Get it perfect - those amps deserve it !

    I passed up an Atomic Space Tone with the built in attenuator for a grand at Elderly recently and I def regret it ! :cry:
     
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