1. Win a Broadcaster or one of 3 Teles! The annual Supporting Member Giveaway is on. To enter Click Here. To see all the prizes and full details Click Here. To view the thread about the giveaway Click Here.

The Amp was Working Better Than It Should Have...

Discussion in 'Shock Brother's DIY Amps' started by NTC, Nov 22, 2020 at 12:19 AM.

  1. NTC

    NTC Tele-Meister

    Posts:
    204
    Joined:
    Mar 17, 2003
    After reading https://www.tdpri.com/threads/fender-cathodyne-phase-inverters.755580/
    several times, I decided I should remove the "Paul C." mod from my three homebrews. I finished the 5F11-ish first, which was built with the mod. After that, I unmoded the 5E7 Bandmaster. I verified it was working correctly and the amp sounded good. I decided to check the bias since I hadn't been in the amp in years - I have a new DMM and am getting used to the OT resistance method. Once I had the primary resistances, I measured the CT voltage, then one if the plate voltages. The voltages were the same! That is when I noticed the tube in that socket was not glowing and was white around where the getter metalization is - no vacuum. What is mystifying is that it sounded good at all. Of course, I couldn't turn it up - perhaps thay would have made the problem more obvious. The old tubes were JJ 6L6GCs. Now it has a pair of Sylvania 6L6WGBs biased at about 73% of max dissipation. I can't wait to turn it up...
     
  2. jsnwhite619

    jsnwhite619 Friend of Leo's

    Age:
    36
    Posts:
    3,234
    Joined:
    Sep 10, 2013
    Location:
    Georgia
    A few months ago I was working on a 5f11 Vibrolux clone and it turned out that only 1 tube was working at the time....I assumed it was the speaker because it was dirty as hell, but not that much quieter than it should have been. As @muchxs says, that first watt does most of the heavy lifting!
     
  3. ThermionicScott

    ThermionicScott Poster Extraordinaire

    Age:
    40
    Posts:
    6,146
    Joined:
    Dec 3, 2005
    Location:
    CID
    It wasn't long after building my 5E7 that I tried it without one of the output tubes, just to see what it would sound like. At low volumes, you basically just have a single-ended amp. Turn it up a little more and it will start crunching up as the remaining output tube starts going in and out of cutoff. Kind of a fun sound, actually! :)
     
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.