Make this amp great again.

Discussion in 'The Workbench' started by Marcell, Jul 10, 2020.

  1. Marcell

    Marcell Active Member

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    Hey there.

    What is advisble when you buy a secondhand amp and wanna do great maintenance on it. It's a amp from the 90's 9100.

    Tubecheck
    Filtercaps?
     
  2. Chris-in-LA

    Chris-in-LA Well-Known Member

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    It’s not a bad idea to check the bias. I would do a visual inspection but that would only tell you if everything looked good. How does it sound?
     
  3. pedecamp

    pedecamp Well-Known Member

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    Power it on and check the bias and see how it sounds. If it sounds bad get new tubes. Also clean all pots and input jacks with Deoxit. Do a visual inspection of the internals to make sure everything looks good, no bulges, burns or leaks. If you got cash to spare have a pro tech look it over if youre not confident to do it yourself.
     
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  4. Marcell

    Marcell Active Member

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    The only experience I have is running a jcm900 on el34 with change of a bias resistor... not in things how to get a amp back to shape..deoxit is something I will do..maybe a needlefile to gently work the connections..jacks and tubesockets. I have a bias probe so that can I do. What to change after 30 years of service?
     
  5. lespaul339

    lespaul339 Well-Known Member

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    Like you said, tubes and filter caps would be the first things to look at. Open it up and look at the filter caps. I'd almost do that before I even powered it on. If you see a bulge or a leak then I'd replace them. It's fairly easy to do yourself and not too expensive of a repair.
     
  6. South Park

    South Park Well-Known Member

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    Start with the basics . If the amp sounds good may not have to do much .
     
  7. Chris-in-LA

    Chris-in-LA Well-Known Member

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    You still didn’t tell us if there’s an actual problem. If the bias checks out and it sounds good, I’d just use it as is.
     
  8. mickeydg5

    mickeydg5 Well-Known Member

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    And it is a model 9100. Its not rocket science but a little different than the run of the mill amplifier.
     
  9. Marcell

    Marcell Active Member

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    Itś a 9200.. I had a 9100... but sold it.
    I just bought it.. I just want to do a great check so I don't have issues later. It has Tung sol tubes so I think thats oke. Other things to look for? I don't like to do repetitions and have problems I could have avoid in the first place... Don't you hate it when some bandmember hasn't sort out his stuff?
     
  10. mickeydg5

    mickeydg5 Well-Known Member

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    So you have baised a 9100 or 9200 before and you know about the balancing?
     
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  11. neikeel

    neikeel Well-Known Member

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    Is this the version that you can run both in stereo and in mono (left side only)? As it is just a power amp there is nothing special. Decent matched quad (per side) of tubes, filter caps in good condition and bias set in correct range for your tubes. I have a 9000 series 50/50 knocking around somewhere, I power it up every now and again to keep it sweet. I am limited in that I do not have a dedicated stereo preamp for it (waiting for something decent but cheap to throw itself at me).
    What are you using for a preamp?
     
  12. Marcell

    Marcell Active Member

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    The Filtercaps are toast... I can move them 1/2 inch...they are wobbeling in there.. 220uF 4 pro side.
     
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  13. Marcell

    Marcell Active Member

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    I'm using a digitech gsp1101 for preamp..
     
  14. Marcell

    Marcell Active Member

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  15. Chris-in-LA

    Chris-in-LA Well-Known Member

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    Not sure that wobbly means anything other than the bracket or solder connection can be loose. Check all the connections. Also, does the amp work? How does it sound?
     
    Last edited: Jul 12, 2020
  16. Marcell

    Marcell Active Member

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    I
    It sounds oke, just noisy pots and lack of power.
     
  17. Chris-in-LA

    Chris-in-LA Well-Known Member

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    Have you checked the bias?
     
  18. Marcell

    Marcell Active Member

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    No, first I want to check thoose caps, maybe resolder them. I have to take it in my shed, to do good observation of whats going on.
     
  19. Chris-in-LA

    Chris-in-LA Well-Known Member

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    Good idea.
     
  20. CoyotesGator

    CoyotesGator Well-Known Member

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    Always check that the fuses are the correct size.
     
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