small bad tube amp going bye-bye

Discussion in 'Amps and Cabs [BG]' started by nil, Mar 13, 2001.

  1. My trusty Jansen Bassman 50 started playing up tonite... :(

    Initially the fuse had blown earlier, so that was replaced. The old Carvin 6L6s that I sometimes run in it were pretty clanky and delivering sod all, so I popped back in a pair of good condition GT 6L6s (which normally give the amp a real boost in the headroom department).

    Now, playing softly is OK, but strike a loud note and the amp distorts...looking behind the 6L6s are dimming when I dig in.

    Is this dodgy output or preamp (12ax7, 12au7) tubes causing this, or something nastier?

    Another question too: why does my Bassman 50 (~62w) have 2 huge electrolytic caps (filters I presume), yet my Bassman 6/35 (~45w) has none? Both run 2 x 6L6s, with 12ax7 and 12au7 preamps and gain stages.
  2. JMX

    JMX Vorsprung durch Technik

    Sep 4, 2000
    Cologne, Germany
    Have a service person adjust the bias, that would be my first guess.
  3. Hmmm, hadn't thought of that...I replaced the 2 old 12au7's with 2 good/used 12ax7's, and it "fixed" the problem, although the amp's breaking up a bit earlier now for some reason.

    Bias would make sense - it runs stupid hot at the moment - and considering it's a 34 yo amp...

    Time for something bigger! :D