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Trouble with Bassman 100T?

Discussion in 'Amps [BG]' started by MetroBass, Jan 18, 2014.


  1. MetroBass

    MetroBass Supporting Member

    Joined:
    Mar 26, 2008
    Location:
    South of LA
    Disclosures:
    Hatred obscures all distinctions.
    I primarily use this for a practice amp but today I allowed a friend to use it at a gig. As a practice amp I run it at the 25W setting and have never had any problems, however, we switched it to the full 100W for his gig.

    When we did this the auto biasing would not lock in. We finally got it to respond and when it did I get a red light, two greens and an orange. Amp definitely doesn't feel like it's delivering 100W. Do I need new tubes?

    I did notice that the power tube closest to the left from the rear was glowing extremely orange.
     
  2. Downunderwonder

    Downunderwonder

    Joined:
    Aug 26, 2009
    Location:
    New Zealand
    Manual probably says something along lines of "when light glows X, replace tube".
     
  3. coreyfyfe

    coreyfyfe Supporting Member

    Joined:
    Nov 19, 2007
    Location:
    boston, ma
    Take it in for service. If the tube was glowing orange (ie plates glowing and not just the heaters) you can have other issues that should be checked to prevent damaging more tubes. Also have them check the bias circuit, apparently that circuit has been a bit of a problem for people.
     
  4. Moosehead1966

    Moosehead1966

    Joined:
    Jun 24, 2009
    Location:
    Sault Ste. Marie, Ontario
    Try a new 6L6. As the manual says, it should bias and settle in. If not, that's where the work begins. Do a search of related threads.

    Marc
     
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  6. MetroBass

    MetroBass Supporting Member

    Joined:
    Mar 26, 2008
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    South of LA
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    Hatred obscures all distinctions.
    Thanks - I have Wing Cs in there but still have the original JJs I'll try tomorrow to see if it biases.
     
  7. MetroBass

    MetroBass Supporting Member

    Joined:
    Mar 26, 2008
    Location:
    South of LA
    Disclosures:
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    Put one of the JJ I had laying around - problem fixed. Looks like Winged C are no longer being made and there's a huge mark up now - $40 /tube.
     
  8. Tim1

    Tim1

    Joined:
    Sep 9, 2005
    Location:
    New Zealand
    So.....this is an example of the autobias circuitry behaving exactly as it should and working to the advantage of the player......:D :D :D
     

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