DRRI losing volume after being on for a while

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by DeaconBlues, Apr 9, 2015.

  1. DeaconBlues

    DeaconBlues Member

    Messages:
    2,990
    Joined:
    May 2, 2007
    Location:
    way down below the ocean...
    By "a while" I mean 2-3 hrs. Volume is strong and then it just fades away. I've tested all tubes on my BK tube tester and all but V1 tested strong. I replaced V1, but the problem is still there. Banging on the amp doesn't seem to help. Flipping the stand-by switch on and off doesn't, either. What does work is turning both the power switch and the standby off and then back on in 15-20 seconds, but even this doesn't always work and the amp loses volume again within a minute or two.

    The amp is an early 90's RI. Could I be looking at bad caps, or is this a cold/bad solder joint issue?
     
    Last edited: Apr 9, 2015
  2. DeaconBlues

    DeaconBlues Member

    Messages:
    2,990
    Joined:
    May 2, 2007
    Location:
    way down below the ocean...
    Edited OP with more info.
     
  3. Jeff Gehring

    Jeff Gehring Silver Supporting Member

    Messages:
    4,196
    Joined:
    Jan 17, 2008
    Location:
    Kansas City area
    This has my vote...
     
  4. DeaconBlues

    DeaconBlues Member

    Messages:
    2,990
    Joined:
    May 2, 2007
    Location:
    way down below the ocean...
    Dang! I was afraid that's what it might be. Gonna be a pain to find, but a man has to do what man has to do.:rolleyes:
     
  5. kbgear

    kbgear Member

    Messages:
    1,152
    Joined:
    Mar 31, 2013
    Location:
    SF Bay
    I've had something similar happen because of a bad power tube -- going full off lets the tube cool enough to regain its composure. And the tube tested normal.

    It might be worth temporarily swapping power tubes to check before going through the hassle of circuit tracing? FWIW!
     
  6. DeaconBlues

    DeaconBlues Member

    Messages:
    2,990
    Joined:
    May 2, 2007
    Location:
    way down below the ocean...
    I'll certainly try swapping tubes, kb. Thanks.
     
  7. pdf64

    pdf64 Member

    Messages:
    5,149
    Joined:
    Aug 9, 2008
    Location:
    Staffordshire, UK.
    Is it a smooth clean fade out / in?
     
  8. BudLite

    BudLite Supporting Member

    Messages:
    2,844
    Joined:
    Jul 7, 2005
    Location:
    Upstate, NY
    I was thinking power tubes but you might as well try the rectifier tube as well.

     
  9. DeaconBlues

    DeaconBlues Member

    Messages:
    2,990
    Joined:
    May 2, 2007
    Location:
    way down below the ocean...
    Smooth and clean, but fairly abrupt.
     
  10. oldhousescott

    oldhousescott Silver Supporting Member

    Messages:
    2,363
    Joined:
    Feb 21, 2008
    I had something similar happen in my home-brew DR and it turned out to be a bad rectifier tube. After running a while, the B+ would fall and the amp would cut out. Turning it off and letting it cool a while would restore sound. That was a booger to find.
     
  11. pdf64

    pdf64 Member

    Messages:
    5,149
    Joined:
    Aug 9, 2008
    Location:
    Staffordshire, UK.
    When it's in the fault mode, darken the room and check that all the heaters are getting power.
     
  12. DeaconBlues

    DeaconBlues Member

    Messages:
    2,990
    Joined:
    May 2, 2007
    Location:
    way down below the ocean...
    Good suggestion. I'll try that as soon as I get a chance.
     
  13. DeaconBlues

    DeaconBlues Member

    Messages:
    2,990
    Joined:
    May 2, 2007
    Location:
    way down below the ocean...
    Turns out it was the rectifier tube. Thanks, Scott and pdf.
     
  14. kbgear

    kbgear Member

    Messages:
    1,152
    Joined:
    Mar 31, 2013
    Location:
    SF Bay
    Glad it wasn't a wild solder chase!
     
  15. DeaconBlues

    DeaconBlues Member

    Messages:
    2,990
    Joined:
    May 2, 2007
    Location:
    way down below the ocean...

Share This Page