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Dead 1980 Musicman Sabre bass - what to do?

Discussion in 'Basses [BG]' started by Dave Campbell, Dec 16, 2018.


  1. Dave Campbell

    Dave Campbell

    Jul 13, 2006
    My Sabre bit it a while back, and have been stumped on what might be going on - brought it to a reputable local repair tech recently, and they weren't successful.

    Basically the output went down to almost nothing, new battery - no improvement.

    Most recently I contacted Musicman/Ernie Ball and asked if they could look at it, this was their response:

    Thanks for your interest in Ernie Ball Music Man! It's difficult to say if that model has a history of the electronics issue your experiencing, we do not get many inquires for the pre Ernie Ball instruments. Unfortunately we are not able to offer repair service on a pre Ernie Ball instrument in our factory. We were left with a photo copy of the wiring diagram when we acquired Music Man, we've attached it below if it can be of any help. We do not have any of the replacement electronic parts available through the factory.

    Not very helpful...

    Anyone know what alternatives I might have available?
     
  2. Rabidhamster

    Rabidhamster

    Jan 15, 2014
    electronics repair guy would make quick work of it. Make sure to tell them they need to use as similar composition of components as possible. It could just be a bad solder joint or something, or a failed resistor.

    If it has 2 pickups and the problem is the same with both, thats where I'd start, but if its only 1 pickup make sure there isn't a short in one coil. Hopefully your local repair shop tested the pickup if it is a single


    high res photos in hard light of both sides of the preamp circuit board may let us help you diagnose. If you have a multimeter you can test the pickups yourself but if its a 2-pickup model its unlikely both pickups went bad at once. Still not a bad investment for minor electronic troubleshooting. You can get a cheap-O at harbor freight for under $10


    The LM4250 op amp is still readily available cheaply, so nothing in that bass is unrepairable. A bad pickup would be the most expensive thing to repair.

    What area of the world are you in?

    attachment.
     
    Last edited: Dec 16, 2018
    Dasgre0g, Mistahbenn and Reedt2000 like this.
  3. Dave Campbell

    Dave Campbell

    Jul 13, 2006
    It's two pickups.
     
    Rabidhamster likes this.
  4. Dave Campbell

    Dave Campbell

    Jul 13, 2006
    I'm just outside of Vancouver BC.
     
  5. Reedt2000

    Reedt2000 Supporting Member

    Apr 26, 2017
    Central New Jersey
    Yup, this is what you do ^

    Test the pickups to eliminate them as a source of the issue. Double check the jack just for stupidity's sake (I would assume the tech you took it to did this but you never know...). If those components are good then go through (or have someone go though) the preamp components to locate and repair the failure.
     
    FenderOli and Rabidhamster like this.
  6. mikeswals

    mikeswals Supporting Member

    Nov 18, 2002
    Seattle / Tacoma
    I would open it up and test pickups with a multimeter for output, and start looking for bad or broken connections and bad switches and pots and capacitors.
    Is the op amp chip directly soldered to the board on yours, or is it plugged into a chip holder? The LM4250CN chip is still available and only cost a few bucks, be easy to replace if its just plugged into a holder.
     
    Last edited: Dec 16, 2018
    Rabidhamster likes this.
  7. Dave Campbell

    Dave Campbell

    Jul 13, 2006
    There's an old wizard in Vancouver named Mr Ho from Ho Electric, an amp repair guy... I'm headed through there just before Christmas, perhaps he could be the guy.
     
  8. Rabidhamster

    Rabidhamster

    Jan 15, 2014
    Cool I'd start troubleshooting the pre-amp then. Plug the bass in, amp on tweeters off or roll the treble off, with the control cavity open and carefully wiggle (don't tug) the leads coming from each of the pickups. Any noise or change in situation?

    If no, then I'd start troubleshooting from the jack inward to the pre-amp. A bad soldering joint will be pretty easily visible if you look them up on the internet to see what they look like. But I would expect a reputable repair shop shop should've gotten that, so I'm thinking a component has to be out of spec somewhere.


    Mr. Ho sounds like he'd get you fixed up, or a TV repair guy would think its the easiest thing he's ever done.
     
  9. /\/\3phist0

    /\/\3phist0 Life: It's sexually transmitted and always fatal Supporting Member

    Contact G&L, their factory is where MusicMan started...
     
    Low84 likes this.
  10. Reedt2000

    Reedt2000 Supporting Member

    Apr 26, 2017
    Central New Jersey
    Sounds like that's just the kinda guy who could do it, especially if you have the diagram for it. As others mention parts (other than pickups) should be cheap, labor maybe an hour.
     
    Rabidhamster likes this.
  11. Steve59 and Reedt2000 like this.
  12. mikeswals

    mikeswals Supporting Member

    Nov 18, 2002
    Seattle / Tacoma
    It could very well be a bad op amp chip.
    The original circut board didnt have a diode to protect it from shorts. I thought by late 79/early 80 that the board had the diode by then but yours may not.
     
    TinIndian likes this.
  13. Dave Campbell

    Dave Campbell

    Jul 13, 2006
    Interesting, Caca... One could be installed after the fact, yes?
     
  14. Reedt2000

    Reedt2000 Supporting Member

    Apr 26, 2017
    Central New Jersey
    FenderOli, Miker27607 and Mistahbenn like this.
  15. bassgrackle

    bassgrackle Supporting Member

    Aug 17, 2010
    I’ll take that Sabre off your hands.
     
    Mistahbenn likes this.
  16. Tvrtko

    Tvrtko

    Dec 27, 2002
    South of the USA
    If it faded away, I bet it's 1 microF cap. Those can be suckers in any electronic circuit. Replace all 4 and the one 10uF. That would be easy step 1.
     
  17. john m

    john m Supporting Member

    Jan 15, 2006
    Could just be a bad opamp,
    But a tech could easily determine the problem.
     
  18. Tvrtko

    Tvrtko

    Dec 27, 2002
    South of the USA
    Last thing that dies is the most obvious thing. I always check stupid things: bad caps, bad connections, pots (in this case). I learned my lessons long ago.
     
  19. john m

    john m Supporting Member

    Jan 15, 2006
    Check power then ground, if ok,
    Scope on pin 2 then scope on pin 6 would tell a lot.
     
  20. Inky13

    Inky13

    Nov 13, 2016
    Buffalo NY
    I think Mr. Ho would be an excellent name for a band.
     
    Gaolee, alembicbones, City and 3 others like this.

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