Dean Edge Hammer 4 : How to replace active pre-amp?

Discussion in 'Pickups & Electronics [BG]' started by whmeeske, Feb 12, 2018.

  1. whmeeske


    Feb 12, 2018

    I have a Dean Edge Hammer 4 bass and I want to replace the active pre-amp because the Bass and Treble controls aren't doing anything. I did have this checked at a guitarshop, but they couldn't find something wrong and said it's probably normal behavior...

    I did some research on the current configuration of the electronics in my bass and found out that it uses a RBA-04M as pre-amp. After some googleling I found the wiring diagram of this specdific pre-amp. Using this wiring diagram I noticed some anomalies in the actual configuration in my bass:
    • The ground isn't daisy-chained between all 4 control pots, but seems to be splitted between Volume & Balance control pot and the Bass control pot & both pickups & the output jack connector. The Treble control pot isn't even connected to ground at all.
      --> Could this explain the malfunctioning of the Bass and Treble controls?
    • The red+white wires of both puckups are soldered together (considering both pickups are passive humbuckers with coils connected in serial), but these 2 wires of the neck pickup are soldered together on the output pin of the jack connector and these 2 wires of the bridge pickup are soldered together and put somewhere behind a piece of tape.
      --> Should I remove the soldered red+white wires from the output jack connector?
    • Using a multimeter I measured a short circuit between the output pin and the ground pin of the jack connector.
      --> What could be the reason of this? For me it doesn't seems very logical, because why should one put the output signal to the ground?
    I have done a search for a replacement of the pre-amp and the controls and I have found a Glockenklang 2 band EQ that comes with 4 control pots, the same as in my actual configuration. Can this be a good replacement for my bass? The reviews are looking good.
    The wiring diagram looks pretty simple, I only have to find out which wire of the pickups (green or black) is the output of the pickup that I have to connect to the Balance control pot together with the ground wires of both pickups.

    I hope someone with some experience in this matter can give me some advice.
  2. B-Mac

    B-Mac Just like Aretha Sang... R-E-S-P-E-C-T Supporting Member

    Visit: Dean Club!!!

    Introduce yourself and look up eastcoasteddie.

    He's done a lot of work on his DEAN Sledge Hammer bass, which granted isn't the same, but it is similar. I am sure he can help you out.

    Last edited: Mar 6, 2018
    whmeeske likes this.
  3. You are correct in that the red & white wires soldered together are for pickup coils in Series. However, you must remove the neck pickup wires from the output jack pin. The red/white wires should be taped off like the bridge pickup wires.

    The jack has three pins, Tip (+), Ring (-), and ground. Tip is the “output” and the wire coming off the volume pot should be connected here. Ring , the (-) terminal, should have the black (negative) from the 9v battery attached here. Ground is self-explanatory.

    What kind of jack do you have? Open switchcraft type or closed barrel type?
    The closed barrel type have more tendency to short circuit inside. You cannot fix them, just replace...

    If you replace the jack and get some of the wiring fixed, you can probably get the original preamp going again, but it is a cheap generic preamp...

    You can’t go wrong with Delano electronics. I have had great success with Bartolini preamps myself.

    For pickups typically, black is hot, green would be ground when wired in Series. A neat auxilliary function you can add (depending on how adventurous you are) is a coil-tap switch. This would basically take the red/white wires and connect them to ground, cancelling out one coil and making the pickup a single coil. You can also wire the pickups in parallel (red/black as hot, white/green as ground)
    Last edited: Mar 6, 2018
    whmeeske and B-Mac like this.
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