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TBP-1 preamp: plug in foot switch causes amp to be mute

Discussion in 'Amps and Cabs [BG]' started by LeeLuu, Jun 21, 2019.

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  1. Jun 21, 2019 #1
    LeeLuu

    LeeLuu

    Jun 21, 2019
    Hi Forum. This bass preamp comes with a 4 switch foot switch. As soon as I plug in a cable in to the foot switch socket the amp goes immediately mute and the indicator lamp is flashing at the front panel. As it would when pressing the mute button on the front for muting. Other then that the amp functions perfectly except if I plug in the foot switch cable. I did release (off position) all knobs at the front panel as it is mentioned in the manual for proper functionality of the foot switch.
    By checking the control lamps at the front panel I can see that the first 3 foot switch knobs do work except the mute switch is not triggering. The problem I thing is on the amp itself since it already mutes by plunging in the jack at the back (with ore without the foot switch attached). What could be the cause?

    By looking in the electrics I can see a connection which I'm not sure it should bee like this. Maybe a professional electrical person could tell my if this is suppose to be like this.
    Thanks a lot!

    http://pick.elbow.be/TBP-1/TBP-1-mute-switch.png

    [​IMG]
     
  2. Jun 21, 2019 #2
    agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    That's likely correct, but why not ask the manufacturer? They would know for sure what might be wrong. Fender is excellent at supporting their products, they have a good network of authorized service centers first.
     
    jastacey and eff-clef like this.
  3. Jun 21, 2019 #3
    BrentSimons

    BrentSimons

    Mar 4, 2004
    Vergennes,VT USA
    is the cable fixed to the footswitch or is it separate? I think it uses a TRS cable? Perhaps the cable is faulty.
    Best wishes,
    Brent
     
    BassmanPaul likes this.
  4. Jun 21, 2019 #4
    LeeLuu

    LeeLuu

    Jun 21, 2019
    Original it is a TS Cable it's sound, good and separat. Also tried others.
    I tried to post at the Fender forum but somehow got no replay. Is there a direct service email?
     
  5. Jun 21, 2019 #5
    agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    Where are you located? There are service centers all over the world.
     
  6. Jun 21, 2019 #6
    LeeLuu

    LeeLuu

    Jun 21, 2019
    Bought it in NY but I live in Switzerland.
     
  7. Jun 21, 2019 #7
    BassmanPaul

    BassmanPaul Inactive

    Aug 25, 2007
    Scarborough Ontario Canada
    if the foot switch cable is detachable and a standard phone plug cable try a TRS version as Brent suggested in post #3. Upon reading the OP, my first thought was wrong cable. :)
     
    thetragichero, BrentSimons and agedhorse like this.
  8. Jun 21, 2019 #8
    agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    Fender Europe has service centers in Switzerland.
     
    eff-clef likes this.
  9. Jun 21, 2019 #9
    Nighttrain1127

    Nighttrain1127 Supporting Member

    Nov 27, 2004
    Near Worcester MA
    I also believe that Brent and Paul are correct and that the proper cable for that switch is a TRS. I know the cable for the 3 button switch for my Fender bassman 300 PRO is TRS.
     
    BrentSimons likes this.
  10. Jun 21, 2019 #10
    BassikBrad

    BassikBrad Bass Face Brad Supporting Member Commercial User

    Mar 28, 2018
    New Mexico
    Endorsement: Mozztronics. Lusithand
    I have a TBP 1 & whilst I don't have a footswitch & can't help with that, the area that you have marked with
    an arrow, is good, mine is exactly the same. The solder joint flowing between the IC & resistor is Ok.
     
  11. Jun 21, 2019 #11
    agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    I just looked at my documentation and it shows a standard 1/4" TS connection.

    There's a lot of level shifting and detection going on in the footswitch circuit, if you continue to have problems with a known good cable, you are better off having a qualified Fender service tech look at it.
     
  12. Jun 21, 2019 #12
    Nighttrain1127

    Nighttrain1127 Supporting Member

    Nov 27, 2004
    Near Worcester MA
    If Agedhorse says so then it is so.
     
    BassmanPaul, Clutchcargo and BrentSimons like this.
  13. Jun 22, 2019 #13
    LeeLuu

    LeeLuu

    Jun 21, 2019
    Hi thanks for checking BassikBrad! The thing ist the service centers here would have to send it all the way back to the US and it takes ages. It actually never worked from the day on I bought it but I never had the need to use a footswitch. Now years later I figured out that the use of the switch would be very handy. Agedhorse, could you point out or mark more specific where and what of the level shifting process maybe damaged? I attached the electric plan I found on the net and a picture of the amp inside.

    inside.png

    electric.JPG
     
  14. Jun 22, 2019 #14
    beans-on-toast

    beans-on-toast

    Aug 7, 2008
    The problem could be within the footswitch. I would look there first. A local tech should be able to check this out. You could have an out of spec component, or a bad solder joint if it never worked.

    As mentioned, the schematic indicates that you should be using a standard instrument cable. Test it with a short patch cable if you have one, not a long cable. The voltage levels that the amp is requiring are set by the diodes.



    0AFD2D05-9EA3-4E76-AA4A-4DB44BAE510A.jpeg
     
    Last edited: Jun 22, 2019
  15. Jun 22, 2019 #15
    mazdah

    mazdah

    Jan 29, 2010
    Ostrow Wielkopolski, Poland
    Use normal instrument (mono) cable for foot switch.

    Try both positions of front switch before plugging foot switch

    Should work.
     
  16. Jun 22, 2019 #16
    agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    Basic circuit analysis and measurements will indicate the fault. It's a tricky circuit but once you understand it, the troubleshooting is quite straight forward. You will absolutely need a DMM and circuit theory though.
     
  17. Jun 23, 2019 #17
    BogeyBass

    BogeyBass Inactive

    Sep 14, 2010
    Usually diode issue. Depends

    Diodes hardly go bad in the application
    Usually solder connections.

    Check small switching diodes or zeners associated with mute function. Or ribbon cable connections from footswitch board to main board
     
  18. Jun 23, 2019 #18
    agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    Or make measurements and troubleshoot the circuit. It could be a problem with either the pedal or the amp.

    Guessing is not a productive way to repair amplifiers.
     
  19. Jun 24, 2019 #19
    LeeLuu

    LeeLuu

    Jun 21, 2019
    I'll check on the footswitch first using the picture from beans-on-toast ;-). I learned that it is mostly the footswitch not the amp.
     
  20. Jul 31, 2019 #20
    LeeLuu

    LeeLuu

    Jun 21, 2019
    A professional did check the foot switch now and found out that everything in the electronic is ok but the inscription of the outer body case is not matching the one written on the circuit board (picture)!
    "Gain, FX Loop, Vari-Q and Mute" would be correct for the TBP-1 but the board inside indicates
    "Channel Select, Drive/More Drive, Effects, Reverb". So my conclusion: they messed up at the production but the foot switch should actually work on a different amp (but which one?).
    So my question is now: Any idea where I can get a right circuit board ore is there a simple fix/batch I can do on this board it works with the TBP-1?
    To find an buy only the correct footswitch is like winning a jackpot.... :-/
    Thanks
     

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