Replacing pots on a Fernandes APB-5 FRB

Discussion in 'Pickups & Electronics [BG]' started by JimBobBass, Feb 22, 2021.

  1. JimBobBass

    JimBobBass

    Dec 9, 2020
    UK
    Hi,

    Love my Fernandes 5 string, but the pots need replacing.
    The pickups are FGIs

    Q. Replacing pots oneself - do it yourself or take to the luthier? I can manage a soldering iron and spanner
    Q. How do I work out which pots to buy?

    Your wisdom appreciated.

    Cheers
    James
     
  2. rojo412

    rojo412 Sit down, Danny... Supporting Member

    Feb 26, 2000
    Cleveland, OH.
    The ease of this job definitely depends on the configuration of the preamp: some have pots that are mounted directly to a circuit board, some have pots that are separate and only connected with wires. Both can be replaced, but it's harder with the board-mounted version.

    Do you have any pics of the preamp?

    As for what to buy, typically you'd be looking to match what was in there if it's just a matter of them needing to be replaced because they are bad. For example, if it's the volume pot and what's in there is an A250k, that's what you'd want to get for replacement. Pretty much every pot will have a rating printed or stamped on it somewhere.

    Knowing how to use the soldering iron is pretty much the major skill. The thing to remember is to try and attach the wiring with quick and efficient movement, so as not to heat the pot up too much. And you'd basically be doing what you can to try and match the wiring as it was, assuming it was working properly.
     
  3. JimBobBass

    JimBobBass

    Dec 9, 2020
    UK
    Thanks Rojo - great advice. Let me take the back off, have a root around, take some pics and I'll let you know what I find.

    More anon
     
  4. JimBobBass

    JimBobBass

    Dec 9, 2020
    UK
    Hi Rojo,

    It's a rat's nest in there.
    Have decided to replace with a Wilkinson Active Bass EQ - all wired up. Just need to install.

    Might ask for some wiring advice
     
  5. rojo412

    rojo412 Sit down, Danny... Supporting Member

    Feb 26, 2000
    Cleveland, OH.
    Okay, I'll keep my eyes peeled on the thread.
     
  6. JimBobBass

    JimBobBass

    Dec 9, 2020
    UK
    Hey Rojo,
    How's Cleveland this weekend.

    Here are some images.
    The wiring diagram is pretty clear although I don't understand how to wire the pickups to the Balancer Volume.
    The Balancer pot in the diagram shows only 5 connection points.

    WKA-400 Pickup wiring diagram.jpg

    The Pot itself seems to have 6. Belnder pot connections ii.jpg

    Not sure where to connect the neck and the bridge pickup wires.

    And one other question - on the Master volume pot there is one wire coming of it (in the diagram and the actual hardware itself) - I assume that is to go to the bridge for grounding.

    All help gratefully received before I make a complete idiot of myself.

    Cheers
     

    Attached Files:

  7. rojo412

    rojo412 Sit down, Danny... Supporting Member

    Feb 26, 2000
    Cleveland, OH.
    Sorry for the delayed reply, but hey... TB was on fire or something!?!?
    From what I can see of the diagram, this is the important info:

    Screen Shot 2021-04-04 at 4.45.23 PM.png

    The writing on the picture (or on the actual pot) may be clearer in person, but just observing how it looks to be set up, that should be the orientation.
     
  8. JimBobBass

    JimBobBass

    Dec 9, 2020
    UK
    Thanks Rojo.

    I think I have worked it out.
    The blend pots lugs are three on top, three on bottom
    The left bottom and right top lugs are connected by a pre-soldered wire (as shown in the photo above).
    The Top left and Bottom right lugs are grounded to the pot.
    The middle top and bottom are both free.
    My neck and bridge pickups have a red and a white wire, with some metal shielding.
    Making sure I connect neck to the top lugs and bridge to the bottom, and don't cross over... Red goes to middle. White and the metal shielding to the grounded lugs.

    I think that should do it.
     
    rojo412 likes this.
  9. JimBobBass

    JimBobBass

    Dec 9, 2020
    UK
    Hi Rojo,

    Thanks again for your advice.
    An update. I wired everything up - no sound. Double checked - no sound. Swapped round the battery connections, just in case - no sound.
    So finally took it to a friend, who knows about electronics.

    He did all the same things as me. No sound.
    Then he realised that the pickups were active, not passive and needed the appropriate connection to the battery.
    Don't know what he did, but at last it works!