Bias Points for Custom Twin (15) RI

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by mbruffey, Jan 22, 2006.


  1. mbruffey

    mbruffey Member

    Messages:
    275
    Joined:
    May 22, 2005
    Location:
    Twin Cities
    On the Fender Custom Twin 15, a couple of brief questions, since the bias pot seems to be available through a hole in the underside of the chassis (please correct me if I am wrong--I looked up under a couple at GC today):

    (1) What kind of tool does one use to adjust it (philips, standard, etc.)?

    (2) Where are the bias points? That is, seeing that you can adjust the bias from outside the chassis, it is implied that you can also TEST the bias from without--but I don't see a way. What's the point?

    (3) Based on (2) above, should I get a Weber Bias Rite or something like that?

    Thanks,

    Mark
     
  2. Dave C

    Dave C Gold Supporting Member

    Messages:
    1,359
    Joined:
    Jun 10, 2005
    Location:
    Waterford Ct
    Fender amps usually take a flat blade screwdriver to adjust the bias pot. Most Fender amps do not have external test points for bias.The Weber Bias Rite or similar type tool provides the test points and generally work pretty well.
    Dave C
     
  3. mbruffey

    mbruffey Member

    Messages:
    275
    Joined:
    May 22, 2005
    Location:
    Twin Cities
  4. mbruffey

    mbruffey Member

    Messages:
    275
    Joined:
    May 22, 2005
    Location:
    Twin Cities
    Just to be sure, can someone verify that the hole in the chassis of the Custom Twin Reissue is actually for the BIAS pot and not for the HUM ADJUST? I don't have the amp in front of me (thinking of buying one) but the chassis layout from fender shows two trims in the same general vicinity on the board. I'd hate to move the hum adjust by mistake! Mark
     
  5. Dave C

    Dave C Gold Supporting Member

    Messages:
    1,359
    Joined:
    Jun 10, 2005
    Location:
    Waterford Ct
    Moving the hum adjust won't hurt a thing but it won't adjust the bias either, find the one that affects the bias which you'll see on your Bias Rite . After completing the bias adjustments turn the amp up fairly loud and listen for hum, use the hum balance adjust so you hear the least amount of hum and you're done.
    Dave C
     

Share This Page