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Problems with L-2000 single coil mod

Discussion in 'G&L Bass Forum' started by rotassator, Oct 1, 2008.


  1. Help!

    I've never been entirely at home with the tone on my L-2000 (circa 1987) and found the reference to the mods here a while ago.

    I finally bit the bullet and enlisted a mate to do the single coil (inside) / parallel / single coil (outside) mod. It took a while to source a 3-way switch that matched the Digi Key CKN1139-ND mentioned in the mod wiring document (so I bought two).

    The original switch has been removed and the new one installed but something weird is happening. The selected pickups are being affected by the bass tone knob as follows:
    • parallel mode: when selecting pickups, some tone change but all coils remain active
    • single coil modes (bass knob on full): lack of volume, rear coil on both neck and bridge pickups not working
    • single coil modes (bass knob backed off a bit): marked increase in volume, inside / outside modes working as expected and switching properly

    I'm assuming that either something's wired incorrectly, or something's been disturbed in the process. We can't see anything wrong according to the wiring diagram in the document, but this is just weird.

    Any ideas? Please help! :confused:

    Steve
     
  2. Anyone?
     
  3. So... I'm guessing that no-one has any handy advice about this one.

    If anyone has any info, it'd be greatly appreciated.

    For now, I guess I'm leaning towards returning the switch to the stock setup. Shame. I was hoping to get the single-coil mod happening.
     
  4. Daveplaysbass did a single coil mod circuit. He's a member here, but doesn't check in very often. You might see if you can contact him.

    Ken...
     
  5. millahh

    millahh Supporting Member

    Sep 20, 2005
    Hoboken
    How clean is your soldering job? Do you have a short between and of the terminals on the switch from excessive solder?

    I know the diagram is correct (assuming you used the one in the FAQ from daveplaysbass), because I followed it, and had great results.
     
  6. sunbeast

    sunbeast Supporting Member

    Jul 19, 2006
    Los Angeles, CA
    I've been trying to figure out what you might have done, but I really can't! Its almost certainly a weird ground or a phasing problem. You should test to see which coils are actually being selected in all your modes (lightly tapping on the polepieces with a screwdriver will tell you which coils are "hot"). My first G&L was a new L2500 that was wired wrong from the factory- it did some weird things as well, but was easy enough to diagnose when I knew what coils were "hot" in each switch selection. I haven't done that particular mod, but I have done series/single coil/parallel on seperate switches for neck and bridge pickup. I accomplished this by making the volume a stacked neck/bridge volume and replaced the pickup selector switch with the neck coil selector. I haven't had any problems with it, though I mostly used the available diagram to inspire me to do the mod rather than actually following it!

    One thing that he didn't mention in his diagram is that you should reground the copper plate on the bottom of the pickups when you do one of the single coil mods. The way the pickups are wired from the factory, one end of one of the coils on each pickup is always grounded through a connection with the copper plate on the bottom of the pickup (which keeps the pickup shielded to some degree)- this also keeps the polepieces grounded, as they are in a circuit with the plate. When you do the single coil mod, you reverse the orientation of the coils in one of the pickups (which pickup depends on whether or not you chose inner or outer coils for your single coil setting). This means that the copper plate on one pickup will no longer be grounded in some of the coil settings- you might notice that touching the polepieces on one of the pickups in certain settings gives you a nasty buzzing, and this is why. The best way to fix this issue is to ground the copper plates seperately from the coil start- the easiest way is to leave the current wire (I believe it is the "green" wire if I remember correctly) that is connected to the bottom plate on the pickup and connect it directly to ground through the back of a pot or whatever ground method you use, then cut the wire that attaches the pickup plate to the end of one of the pickup coils and solder on a new jumper that will then go to wherever the "green" jumper went in the wiring diagram you are using.

    This probably sounds more complicated than it really is... it is really just a matter of one cut and one solder connection per pickup before doing the single coil mod.

    Karl
     
  7. Thanks for your replies. For some reason, I didn't get any email notifications.

    I'll let my mod guy know and report back with the results. :)
     
  8. DavePlaysBass

    DavePlaysBass Supporting Member

    Mar 31, 2004
    CO

    This is addressed in the latest document up top. Ever since I got into a Tribby with the shielding, I have done the mods so they do not interfer or disturb the pickup shielding. You must be working off a document that is few years old.
     
  9. sunbeast

    sunbeast Supporting Member

    Jul 19, 2006
    Los Angeles, CA
    Ah! Just read the newer version- sorry for the false info! Great document, by the way.

    I've been contemplating ditching the preamp in my L2000 once and for all and using the extra switch/ hole to return the pickup selector to the fold- I'd then rewire the stacked volume pots to Gibson style (switching the input and output lugs) to cut out the extra loading that occurs in the Fender Jazz style blending- I've mostly just been doing one pickup, the other pickup, or both full-on recently (blending can be fairly touchy with 500K pots- there are some great tones, but they are sometimes hard to find again!). With the Gibson style (2 volumes AND pickups selector), I could get 3 fairly volume-balanced tones at the flick of the switch, not including all the different combos of coil combinations....

    You are right about there being nearly endless possibilities with these instruments!

    Karl
     
  10. DavePlaysBass

    DavePlaysBass Supporting Member

    Mar 31, 2004
    CO
    I have a lot hate relationship with the preamp. Usually I don't use. But then I have a day where it makes things sound better.

    As for loading down the MFDs, that is not necessarily a bad thing. Like a lot guys I read on here, I no longer run my volume dimed (or treble or bass for that matter). The MFD just has so much juice across the whole spectrum. It's taken me 6 years to realize the G&Ls have a lot of USABLE tonal variation in the volume, treble, bass adjustments.
     
  11. sunbeast

    sunbeast Supporting Member

    Jul 19, 2006
    Los Angeles, CA
    For whatever reason, I've been on a super "bright-tone" kick lately- my old L2500 seemed to be naturally brighter than my current L2000 (could just be the age- my L2000 is from '82 and the L2500 was from a couple years back). I hiked the pickups up on my L2500 to make the sound as thick as possible, but find myself doing the opposite on the L2000 (have the pickups down nearly all the way). I actually am very happy with the tone of my L2000 as it is now- lowering the pickups seems to add alot more dynamics and high end and lowers string noise- but I'm just a constant tinkerer at heart! I figure I don't use the preamp as is, so why not experiment? I also generally have my treble and bass controls at half or below these days- I no longer have the master volume, so volume is dependant on which pickup configs/blend I'm using.

    Another interesting thing I've done is to raise the polepieces fairly high on the coil that is singled (nearly 1/8"! obviously only possible if you have the pickups set fairly low) and leave the poles on the other coil screwed all the way down- this seems to have a similar effect as the dummy coil in Musicman basses with the neck single coil pickup. You still get humbucking, but with more clarity, as the lowered coil sees less highs (and the raised coil sees more highs) and therefore less highs are cancelled out in the humbucking modes. If I was a slapper, this bass would now be a slappers dream- but its also great for a really grindy, present fingerstyle tone, which is what I've been really digging lately. The new Mesa Carbine doesn't hurt either! My tone has seriously taken a 180 from the deep growly thing I had been doing for years! I'm just glad my G&L is still up to the task and delivering in spades...

    Karl

     
  12. fender3x

    fender3x

    Mar 12, 2006
    I was thinking of doing the mod with a '94 ASAT bass. Should I do anything different with the shielding or grounds than what is in the current document?
     
  13. DavePlaysBass

    DavePlaysBass Supporting Member

    Mar 31, 2004
    CO
    No
     
  14. fender3x

    fender3x

    Mar 12, 2006
    OK, getting closer to doing the mod... At the moment I am leaning toward doing either the DavePlaysBass mod #7 or #8. I have been thinking that, instead of installing one Digi Key CKN1139-ND switch, I might install two mini DPDT 3 position on-on-on switches, so that I could control each PU independently. That would allow me to, for example, do an SC neck pup, with a P or S bridge pup.

    There are lots of DPDT 3 position on-on-on switches around...but what I am worried about is DPB's admonition:

    "BE SURE TO VERIFY THAT THE SWITCH USED performs as...the Digi Key CKN1139-ND does."

    Would two "normal" DPDT 3 position on-on-on switches operate the same as the CKN1139-ND?

    Is there any way to test this...or does anyone know model numbers I could safely order?

    I can more or less follow directions...but an EE I ain't ;-) I can solder, but wiring diagrams take me forever to understand. After about an hour of staring at by DPB's diagram, and another hour of staring at me ASAT's control cavity, I finally understood the #7 mod. I'd like to control S/P/SC individually for each pup...but I want to ad lib on the mod as little as possible ;-)
     
  15. sunbeast

    sunbeast Supporting Member

    Jul 19, 2006
    Los Angeles, CA
    That is how I have my L2000 wired, and I absolutely love it! You can use any DPDT on-on-on switch- the DPDT means "Double-Pole, Double-Throw", which describes the function and is what you need for this mod (just make sure they are both "on-on-on", which a little harder to find than "on-on" or "on-off-on"). Assuming you are either going to ditch the preamp or pickup selector switch (which I replaced on mine with stacked volume for each pickup- ala jazz bass), both of those switches are DPDT "on-on-on", so you'd have one covered (or possibly both, if you decided to do always passive and stacked-volume).

    Karl

     
  16. fender3x

    fender3x

    Mar 12, 2006
    Thanks, Karl. I have seen a bunch of mini 3-position, on on on switches ...at least order-able over the internet. Nice to hear that you love this mod!


    I pretty much like the controls and preamp as they are, so I thought I'd leave them that way, and just add a switch.

    My ASAT is one of the swirl finishes, the kind where the finish comes off in big flakey chips...so I can't really hurt the resale value. What I was planning was to do was to put one DPDT switch where the 4P4T switch is now, and one just above it. I'd drill through where the battery cavity is now to install the 4th switch. I plan to put in a separate battery box, so that I won't have to open the control cavity to change the battery anymore.

    I like having the two eq controls...I am not crazy about having more than one volume control, and I planned to move the battery anyway...so this seemed the simplest way to do it.

    I am not thrilled with the prospect of drilling an extra hole, though, so I am open to suggestions...
     
  17. sunbeast

    sunbeast Supporting Member

    Jul 19, 2006
    Los Angeles, CA
    If you don't use the "active with treble boost" section of the active/passive switch, you could change out either the volume pot or treble cut pot for a push/pull pot (which is basically just a DPDT on-on switch in one) for active/passive, which would free up a hole for another switch (and then you could use the "active w/treble boost"/active/passive switch for one of your 2 coil switches). You could also pull out either the active passive switch or the pickup selector to get the model # for it (should be printed on the side somewhere), which would ensure that you get the correct size and everything (small switches come in several different sizes, and different mounting hole diameters as well).

    Karl

     
  18. fender3x

    fender3x

    Mar 12, 2006
    Now that is an intriguing idea. I am not sure I care whether I have to drill a new hole...but if I don't have to...and it a fact that I have never once used the active+treble boost...so a push-pull pot to go from active to passive might be all I need. Switch is no problem, since I can get one from G&L... speaking of which... What's the difference (aside from about $5 on the website) between a tribby switch and a regular three way?
     
  19. fender3x

    fender3x

    Mar 12, 2006
    Just thinking about having cake and eating it too. Would it be possible to design the circuit so that, for example,

    Neck switch remains stock pup selector

    Middle switch replaced with dpdt on/on/on to do Parallel/SC/Series--neck pup

    Bridge switch rewired to do Parallel/SC/Series--bridge pup

    Volume control stays stock.

    Bass cut pot adds an active/passive push-pull switch

    Treble cut pot adds a push-pull switch that adds treble boost to active mode.

    Would this be possible?

    Has anyone ever drawn up such a wiring diagram?
     
  20. sunbeast

    sunbeast Supporting Member

    Jul 19, 2006
    Los Angeles, CA
    I pretty much play in passive all the time myself, so I've never really payed much attention to the active circuit and generally don't even have a battery in the bass (I know that the active guts are still in the circuit even in passive, so I prefer to keep them from affecting the tone as much as possible!). I'm sure it could be wired as you are suggesting, though I don't really see the point if you never use the treble boost...
    One big concern worth mentioning is that the control cavity on an L2000 is ALREADY packed to near capacity with wiring, pots, switches, and the preamp- I have one stacked pot and one push/pull in mine, and there is literally only JUST enough room to pack the preamp in (G&L glues the pre to the back of one of the pots from the factory). Another concern I would have about your proposal is that the most readily available push/pull pots, the Alpha branded ones, are kinda flimsy feeling when pulled out- I think using one would be fine, but I know from experience that they will tend to turn really easily when pulled out. Alpha pots simply are not the greatest pots in the world, so I wouldn't recommend using a bunch of them in your bass if you can avoid it! Also, the 1 Meg ohm value push/pull needed for the bass cut are not as readily available as other values (Stewart Mac doesn't carry them, though a Google search does bring a couple results).

    Karl
     

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