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Sunn 300T gone completely nuts

Discussion in 'Amps and Cabs [BG]' started by steers b-c, Nov 6, 2005.

  1. steers b-c

    steers b-c

    Aug 23, 2005
    Austin, Texas
    Hello there, I was just wondering if any of you could give me some advice as to what might be going on with my recently obtained 300T. Initially I had a fuse blow, and after replacing it everything was normal. Then, at a gig, 2 more fuses bite the dust. I was worried, but needed to make it through the gig, so I put in 2 replacements and finished the set. I'm now worried this may have been quite the mistake. The next time I tried to use the amp, if I turned the volume up beyond 3 or so instead of reproducing the note I would get shrill feedback that only goes away when I turn down the volume. Also, if I leave the volume down the notes ring but have distortion. I've tried isolating the various power tube pairs as well as trading out the preamp tubes. Any idea as to what else I should be looking at? I love this thing when it is working, but now I'm completely rigless.
  2. protoz


    Nov 30, 2000
    Maybe the trany is on the way out.

    The tubes could be messed up so a new set would be a good idea. They could be rattling when the volume gets too high producing the feedback.

    Take it to a good tech and have them give it a run through. If it's anything like my 1200S then it will be worth it.
  3. steers b-c

    steers b-c

    Aug 23, 2005
    Austin, Texas
    Yeah, that's what I'm afraid of. I wish I could avoid taking the tech route...I'm completely and utterly broke. But such is my luck. And to think, I actually babied this thing; that's not exactly something I tend to do. Thanks for your advice.
  4. Plain Old Me

    Plain Old Me

    Dec 14, 2004
    Turn it on, and when all the tubes are glowing tap each one with a pencil or something gently, and if one sounds different from the rest its microphonic. Other than that my best advice is to take it to a tech.
  5. when you flip the standby on, do all the 3 LEDs behind the powertubes turn green?

    i turned my 300T on at a gig a couple of months ago, and it sounded all crazy...2 of the fuses on the powertubes were out...i have spares so i replaced them and it worked fine. Still works fine.

    I had to replace them once before, seems like if it gets jarred harder than it should...those tiny fuses go out.

    Other than that, its one killer amp...I like it better than my SVT-AV, that got stolen. :mad:
  6. steers b-c

    steers b-c

    Aug 23, 2005
    Austin, Texas
    Yep, I get all green. I've replaced the fuses before with no trouble, so I don't think that's the problem...but at this point, it would be a godsend if it was. I really don't have the cash to be paying a bench fee at this point, let alone get this thing completely fixed. This is almost enough to tempt me into the darkside...a credit card. :bawl:

    Eh, things happen. Thanks for all your help.