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Tube Amp Newbie...Basic Help Needed

Discussion in 'Amp Tech Center' started by Alaman, May 18, 2017.

  1. Alaman

    Alaman Tele-Meister

    129
    Aug 16, 2015
    Sweet Home, Alabama
    Well...thought I'd finish up the post...I followed the instructions in the link and was able to set the bias. Initial reading was 37 mV. After fooling with the bias adjustment which was incredibly sensitive, I went with 41.5mV. Could never hit the recommended 40mv. I read the Tung Sol could run a little hotter than most tubes and by calculation with plate voltage at 375V that's about 7.74 watts per 6V6 idle. Saw between 7 and 8 watts should be good. I played through the amp about an hour tonight and watched the tubes (left back panel off). I didn't see any redplating that I read about. In the end, the amp is fixed, sounds better than before, I didn't get shocked and I learned a little something about tube amps along the way. All good!
     
    Steve 78 and Believer like this.
  2. corliss1

    corliss1 Tele-Holic

    853
    Sep 13, 2008
    Lansing, MI
    Awesome - good job!
     
  3. Alaman

    Alaman Tele-Meister

    129
    Aug 16, 2015
    Sweet Home, Alabama
    Well I hate to resurrect this thread but one month later my Super Champ X2 is having same symptoms. After the tube change, everything was great for a month and now today while practicing the sound level when down to nothing out of the blue for several seconds then slowly rose to normal. I checked all my connections and started to play again. Worked for a while then sound level went way low again. Came back. Went down to nothing. Seconds later came back. I turned the amp off. I'm now worried I have some deeper problem with the amp that's affecting the tubes. Surely I didn't just have bad luck and blow another tube. Is there anything I can test or check or is it time to take to a tech?
     
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  5. exactopposite

    exactopposite Tele-Meister

    125
    Dec 31, 2010
    Philly
    DId you put in the new 12ax7 when you replaced the 6v6 tubes? If not, give it a shot and see what you get.
     
  6. Alaman

    Alaman Tele-Meister

    129
    Aug 16, 2015
    Sweet Home, Alabama
    Yes...thanks. I replaced all the tubes with Tung Sols...the 12AX7 and 6v6's.
     
  7. bettyseldest

    bettyseldest Tele-Afflicted

    Nov 13, 2011
    UK
    When you got the new tubes did you test all combinations to see if only one of the power tubes was gone? If so you could swap tubes to find if one of the new ones is gone Perhaps onesocket is repeatedly blowing? I'm a newbie too, have never swapped a tube, just thinking out the options. Best of luck.
     
  8. exactopposite

    exactopposite Tele-Meister

    125
    Dec 31, 2010
    Philly
    I would try reseating the tubes which is just pulling them out and putting them back in. Sometimes the sockets the tubes plug into aren't making good contact. Even if that fixes it I think it's time to see a tech. if it's a socket they can be retentioned or replaced.
     
  9. robrob

    robrob Poster Extraordinaire Ad Free Member

    Dec 29, 2012
    United States
    Yes, clean and re-tension the tube sockets.
     
  10. Alaman

    Alaman Tele-Meister

    129
    Aug 16, 2015
    Sweet Home, Alabama
    Thanks will give that a shot tomorrow. Any recommendation on cleaning method? Is DeOxit good enough?
     
  11. robrob

    robrob Poster Extraordinaire Ad Free Member

    Dec 29, 2012
    United States
    Spray DeOxit on the tube pins and insert, repeat.
     
  12. Alaman

    Alaman Tele-Meister

    129
    Aug 16, 2015
    Sweet Home, Alabama
    Took out all the tubes and sprayed connectors with DeOxit. Inserted and removed tubes several times. Noted that they were tough to insert and remove but became much easier each time. Not sure if lubricating effect of DeOxit or they had some corrosion getting cleaned. I took opportunity to clean the speaker connections with DeOxit as well. Put everything together and practiced for an hour without issue. Not calling it a fix yet but sure is looking good so far. If it does the trick then I'm kicking myself for not doing this with my old tubes before buying new. Unfortunately I threw away my pair of 6v6 Ruby tubes I replaced. They may have been okay after all if this was a connection issue.
    Thanks for the suggestions and help! Keeping my fingers crossed. I was already looking at prices on Princeton 65 RI last night. Would love one eventually but not ready for spending a grand quite yet. This SCX2 gets close enough to satisfy me for now for a lot less money.
     
    robrob likes this.
  13. corliss1

    corliss1 Tele-Holic

    853
    Sep 13, 2008
    Lansing, MI
    yay for progress! Glad you at least found out *something* even if it's not a permanent fixt, but I'd hope that after an hour it would be.
     
  14. Alaman

    Alaman Tele-Meister

    129
    Aug 16, 2015
    Sweet Home, Alabama
    Well...played it hard another hour today. Looks like a fix. Amazing that it just happened. I guess vibration and corrosion caused issue with full connection. I'm betting this was present with old tubes. Thought there was something when the tubes were so much easier and smoother to insert after the DeOxit and inserting/removing several times. Again, kicking myself for throwing the old tubes away but counting my blessings that I'm back in business with the amp! Thanks again for the advice!
     
    corliss1 and robrob like this.
  15. Silverface

    Silverface Poster Extraordinaire Ad Free Member

    Age:
    65
    Mar 2, 2003
    Lawndale CA
    Good -

    And just so you understand - the power tubes run on several hundred volts DC. When biasing by the method you used (probes at the power tubes) if your probes slip you can suddenly short that voltage and get a huge spark - and this is where some get shocked, touching the wrong thing in surprise.

    "Getting lucky" is OK, but it's no substitute for basic safety awareness.

    I suggest you learn what can be touched and what can't - and when. The filter caps need to be drained when doing most types of service; they can retain high voltage for some time even when an amp is turned off - and unplugged.
     
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