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Just picked up a working vintage B25 for $350

Discussion in 'Amps and Cabs [BG]' started by da old guy, Nov 27, 2017.

  1. Guessing its pre Maganvox. Serial # BB8713xx. Anyone know what the year or mfg might be or if its a blackline or blueline model? The faceplate is so worn there is not a mark left on it.

    Attached Files:

    jazzbass_5 and mrb327 like this.
  2. acubass


    Oct 10, 2007
    Albuquerque, NM
    It looks a lot like my Blue-line.

    The switches left to right are Polarity and power. My standby is on the back. The head runs at 16Ohms. My serial #is 093679
  3. Does the polarity switch reverse the ac power input polarity or the audio output polarity? i cant detect any difference in the sound when changing the polarity sw.
  4. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    Polarity is for line hum. It should be set to minimize noise. If you can’t hear a difference with the settings, you don’t have line noise.

    You may find a replacement front plate at fliptops.net. Your knobs are not original.

    Sales literature which includes into on the B25 is in the TB Ampeg Portaflex Wiki literature section. Follow the links at the top of the page to click below.

    Sales Literature and Advertisements | TalkBass.com

    The wiki also has the B25 schematic.
    brokencode likes this.

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