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Babysitting my friends 60's EB-3

Discussion in 'Basses [BG]' started by petrus61, Oct 2, 2013.

  1. petrus61

    petrus61 Supporting Member

    ...and I can't seem to find much info on how to date it. I also can't find any others that just had a pickup selector where the varitone would usually be. I'm trying to find the appropriate wiring diagram so I can wire it the correct way with the correct pots and cap values. The previous owner thought it would be a good idea to poorly mount a Badass bridge and replace the knobs as well, but everything else appears original except for the lack of varitone. Anyone have any info on this model?
  2. godofthunder59

    godofthunder59 God of Thunder and Rock and Roll Supporting Member

    Feb 19, 2006
    Rochester NY USA
    Endorsing Cataldo Basses, Whirlwind products, Thunderbucker pickups
    Looks like a refinned '63-'65. I looked up the serial # the site said '63-'67 but this bass has the earlier neck pickup cover making it I think a '63-'65. Knobs are not original nor is the Badass II bridge. The selector switch is a common mod done when the varitone crapped out. If it were me I'd install correct black/silver reflector knobs on it and maybe swap out the Badass for a original bar or "evertilt" bridge (depending on the year) the earlier years would have a bar tail piece. Cool bass enjoy!
  3. petrus61

    petrus61 Supporting Member

    Would that mean the pickups are possibly out of phase since the varitone was removed? I was reading there was a coil in the wiring that should be there but it appears gone. Also, the two cap values are .047...shouldn't there be a different cap for the bridge?
  4. godofthunder59

    godofthunder59 God of Thunder and Rock and Roll Supporting Member

    Feb 19, 2006
    Rochester NY USA
    Endorsing Cataldo Basses, Whirlwind products, Thunderbucker pickups
  5. petrus61

    petrus61 Supporting Member

    Anything specific? Here's some until I get home from work:

    I did notice there a black "gasket" of sorts just under the mudbucker. I'm trying to figure what would get it closest to stock tone without the varitone, unless he decides he wants one. All pots are 500k...but it seems the neck tone should be 250k?
  6. It's got the chrome hardware, so that would make it not older than 1966, and since it has the screw-holes for the cover over the bridge, it's a 1968-or-later (before that, the cover was placed between the 2 pickups). As for the "varitone", it isn't a varitone, it's a pickup selector switch. A varitone is a rotary-switch which engages a capacitor with a resistor in your signal, giving you a pre-determined passive EQ setting per position (depends on the value of the capacitor). This is just a rotary-switch which selects which pickup is selected, and if the inductance is applied. The inductance is a choke-coil that strangles the sound a bit, making it less thuddy & deep. The black gasket is there to make sure the pickup cover sits flush with the body. The EB2 I had had one as well, and there it was needed, since it has an arched top.

    As for the wiring, you had a 4-position rotary giving you:
    Neck + choke coil
    Neck + Bridge (choke coil)

    In 1973 they changed the wiring of the rotary to N (choke), N+B (no choke), N, B. And in '78 to N, N+B (series), N+B (parallel), B

    The wiring for this bass should be this, and indeed, the neck-tone is 250K:

    The value of the GA90C Choke varied, but it's somewhere between 250mH and 2H. Trouble is they are EXTREMELY hard to find, as is a fitting rotary switch (they body isn't that deep, a big switch like an allparts one will be too tall)
  7. I disengaged the tone choke out of the circuit in my EB3 and I prefer it better that way.
  8. petrus61

    petrus61 Supporting Member

    I know it's a pickup selector switch and I've built my own 'varitone' circuits for a P bass (although no resistors and only two caps) but Im curious what the closest to "stock" would be since the varitone has been removed. Do the pickups function as they should without the varitone choke or do they need to be wired a certain way to be in phase? There are two .047 (one per pickup) instead of a .047 and .022 that I keep seeing...all the diagrams I keep seeing include the varitone so I have no way of knowing if its wired "correctly" without it...if there is such a thing?
  9. The pickups work as they are, as they are just regular high-impedance pickups (not the Lo-Z like in the Les Paul Signature, they DO need a coil to work properly on a regular amp). An EB0 hasn't got a choke-coil, nor a varitone, and the pickup is wired directly to the volume pot, and that works perfectly. The choke-coil was just an extra option applied by Gibson to make those basses more useful, since the big humbucker all the way to the neck made them very wooly sounding, the choke tamed the low-end, so they had more midrange, and did cut a little bit easier through the mix.

    As for phase issues: the braided outer mantle of the pickup wires should be soldered to the back of the pots (the ground), the inner core to the lugs of the volume pots. Since you're planning on using it without the choke-coil and without the rotary, just use the wiring that is used for the SG guitar:


    As for the capacitor values: if there are 2 0.047's, leave them, chances are it came stock with those caps (0.022 was used, but 0.047 as well). It's just that a 0.022 doesn't bleed as much treble when you roll off the tone (the bigger the cap value, the darker your tone gets when you roll off your tone completely).
  10. petrus61

    petrus61 Supporting Member

    Thank you! That pretty much nails what I was looking for.
  11. petrus61

    petrus61 Supporting Member

    Here's some cavity shots:

    The tone pots have identical numbers which are different from the vol pots, but it looks like they're different anyway. The vols look like CTS style and the tones look like Bournes style. Not sure if the shielding plate is spec or not.
  12. Looks like it should. The brass shielding-tub is legit and original (some basses came with it, others didn't. They had a generic pattern of holes stamped in them, so they could be used for all instruments that used that cavity lay-out, like the SG, melody maker, EB3, EB0,...


    Looking at the codes on the pots, it's a 1968/1969

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