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Acoustic 370 Red Button?

Discussion in 'Amps and Cabs [BG]' started by bray101, Apr 10, 2015.

  1. bray101


    Feb 26, 2012
    So I sold my 370 about a year ago and have been missing it ever since.

    A really clean one popped up on Craigslist and I traded an Ampeg combo I had for it.

    Opened it up to change one of the resistors to a variable trimmer so I can get more clean headroom out of it.

    While in there, I noticed this red button. Anyone know what this is? Probably something basic, but I never noticed it in my old one.


    Attached Files:

  2. Razman


    Feb 10, 2005
    Orange Park, FL
    Press it. You know you want to.....

    Just make sure that's not the button that let's all the smoke out.

  3. bray101


    Feb 26, 2012
    The suspense is killing me.
  4. It turns on the funk....
  5. I saw that too, when looking to re-cap my head. I'm not sure what it is though. I pressed it. ;)

    I am however very interested in this mod however...
  6. Just a guess...maybe to ground out the caps before servicing.
  7. bray101


    Feb 26, 2012
    Hmmmm...interesting. Maybe?
  8. Fernando Costa

    Fernando Costa

    Aug 4, 2013
    Looks like an old thermal relay button.
  9. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
  10. Can't help you with the button but I am immensely curious as to this change.
  11. bray101


    Feb 26, 2012
  12. bray101


    Feb 26, 2012
    I set mine to around 540 ohms and now I can turn it up almost to 3 without it clipping! Haha. You can set it even lower (approx. 490) but then it starts to run pretty hot and I'd be too scared of the thing melting out.

    In acoustic control land, I think that's quite a feat.
  13. bray101


    Feb 26, 2012
    Essentially, it is just replacing R319 on the original circuit (fixed at 680 ohms) with a 1k variable trimmer (set around 540) so you have adjustable bias instead of the factory set fixed bias. Post #35 on this page helps as well. JohnK explains it well. I believe he is on here somewhere as well.

    370 Bias Wrong in 270, 300, 370 Forum

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