Aguilar DB359 Question

Discussion in 'Amps and Cabs [BG]' started by joshmickelson, Jan 8, 2009.

  1. joshmickelson


    Nov 19, 2008
    Denver, CO
    Hi all! I had a quick question on this unit. I use this with an Ampeg 410 8ohm cab. It’s played approx 4 hours a week (mainly church). Last night, during service, it was cutting in and out of signal and was acting VERY sensitive to my bass, ie it was distorting and almost sounding like a blown speaker (we tested, and the cab is just fine, not blown at all). I am thinking it’s a tube issue, but wanted to see if anyone else here had experiences with these. We have tried a different bass, different cab, and it’s still doing it. One thing that concerns me, is it LOOKS like all of the tubes are lighting up, but I don’t know if I can see them all. So my questions are:

    -How often do you change the tubes on your bass heads?
    -Does the fading in and out/distorting problem sound like something tubes would cause?

    Thanks a bunch!
  2. esoxhntr

    esoxhntr Supporting Member

    Jun 21, 2007
    Markham, Ontario

    When you flip the standby switch to on, give it a nudge or light pull to the right on the way up. Sometimes the standby switch gets dirty and needs to have contact cleaner applied, but try this first to see if the switch is at fault. Worked like a charm on mine, and I was having exactly the same problem.

    If this works, you need to either clean or replace the switch.
  3. joshmickelson


    Nov 19, 2008
    Denver, CO
    thanks a ton! I will try that when I get home.
  4. joshmickelson


    Nov 19, 2008
    Denver, CO
    ps, that makes total sense, because I have noticed before that sometimes when I have the standby on, it still lets a little sound through.
  5. Pickebass

    Pickebass Supporting Member

    Jul 12, 2004
    San Antonio, TX
    There is a pico fuse inside the unit, that can go bad and will eventually need to be replaced. This fuse is inside the unit and needs to be soldered. Check the glow on each tube. If a tube is going bad, the glow will be different. Also, check the biasing on the tubes. It may need to be rebiased. I don't remember the settings, but call Aguilar and they will help you
  6. Dave B.

    Dave B. Guest

    Nov 8, 2003
    Hey Guys,

    In the older units there is an internal pico fuse. If a power tube is not working properly, the fuse may short and a new fuse will need to be installed. However, the fuse itself doesn't go bad, and will be fine unless it's called upon to protect the circuit. It's basically a back-up protection system. If it does pop, no sound will come out of the amp until the fuse is replaced. In the later DB 359's we designed a "smart card", which could be reset.

    IME, it's pretty hard to tell from the glow of a tube much about how they are working-unless there is an obvious hot spot.
    I vote for having a tech test the tubes. You could easily have a tube that needs to be replaced. Checking the bias is a great idea to do in any case. Jot us a note at [email protected] for instructions.

    Hope this helps.

    Happy New Year!

    Dave B.
  7. joshmickelson


    Nov 19, 2008
    Denver, CO
    Wow, thanks for the replies, Dave and Pickebass! I am re-tubing it, because it needed it anyway. I will check that fuse and rebias it as well. Thanks!
  8. paulerip


    Oct 16, 2008
    Nashville, TN
    Aguilar, Ernie Ball, Spector, Seymour Duncan
    I had a very similar issue with mine a few weeks ago - sounded like almost the exact same problem. I took it into the shop and all it was was a ground connection that had gone bad and needed to be replaced/re-connected (only charge was the bench fee). You might want to check that out prior to spending the $$ on new tubes.
  9. DaveAceofBass

    DaveAceofBass Supporting Member

    Feb 20, 2004
    Charlotte, NC
    Your preamp tubes could be going. Take off the top lid and tap on each one. In particular, check the 12AU7. (It has a cover on it, so take that off first.) I've had the scratchy problem too, but replacing preamp tubes fixed it right up.