Making a Tribute L-2000 an L-2000 Plus

Seeing as how we are fortunate to count Paul Gagon as a member here, it seemed like a good time to give him a home to stretch out in and relax a little. Maybe exercise the grey matter and present a little history of the guitar and bass (amps too!) from his perspective as one of the eminent designers of our time.

Got questions? Great! Good questions might be, "What kind of windings are on the S500 pickup and why?" Or, "What was the thought process behind the MJ-4?" Troubleshooting questions should remain in the regular forums (he reads those too). Finally, please be mindful of how I feel about tech questions via PM or email.

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Re: Making a Tribute L-2000 an L-2000 Plus

Postby GeorgeB » Wed Oct 24, 2018 2:30 am

Paul, you didn't post a schematic but from the wiring diagram I gather you did not use the simplest arrangement for the PU config switches which would have been a simple single pole on/off/on toogle to short out one of the coils (or none) which also would have the advantage of a visual coherence beetwen switch setting and activated coils (switches would need to be rotated a bit to resemble more like a neck/middle/bridge thing, visually)

Anyway, to implement switchable OMG we just need to insert the OMG cap in the shunt path, actually two individual (and likely different) caps for each coil could be used, even combined with resistors for more subtle effect. Then a push-pull pot could short out these series elements. There are many possibilities...
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Re: Making a Tribute L-2000 an L-2000 Plus

Postby Paul Gagon » Wed Oct 24, 2018 5:01 am

b17krk wrote:The more I think about this mod the more I'm itching to give it a go, however the one thing niggling at the back of my mind is the necessity to add an extra switch. I'm not sure I feel comfortable drilling another hole in my L2K because it just sounds too permanent to me. That said I have been trying to envisage an alternative way of getting similar results, whilst at the same time reserving the ability to return it to it's original configuration should the need arise, and have come up with the following scenarios:

a. One option would be to remove the preamp and convert the bass to passive only. This way I could potentially utilise the Active/Passive switch as a coil selector for one of the pickups.

or...

b. Use a pull/push pot (volume pot) to switch between active and passive (thus losing the treble boost functionality). This way I could potentially utilise the Active/Passive switch as a coil selector for one of the pickups and keep the ability to use the preamp should I ever need to.

What I would really like to know is if any of this is remotely possible - and if so (as I'm a complete beginner when it comes to electronics) could somebody in the know help by providing a diagram of some description just to get me started please?

First off, let me just say I love your spirit of adventure and desire to give this a go. Both of your options are doable, and of the two, I would pick option B. I’m in the middle of a few projects right now but give me a moment and I’ll draw up a wiring diagram that shows your option B.

I really think your going to love the wide array of tones that open up when you add this switching mod. Again, thanks for being willing to explore the jungle that is bass modification.

Paul
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Re: Making a Tribute L-2000 an L-2000 Plus

Postby b17krk » Wed Oct 24, 2018 10:41 am

Thank you Paul, I really appreciate you taking the time to help out. You are a true gent!
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Re: Making a Tribute L-2000 an L-2000 Plus

Postby Paul Gagon » Wed Oct 24, 2018 11:24 am

GeorgeB wrote:Paul, you didn't post a schematic but from the wiring diagram I gather you did not use the simplest arrangement for the PU config switches which would have been a simple single pole on/off/on toogle to short out one of the coils (or none) which also would have the advantage of a visual coherence beetwen switch setting and activated coils (switches would need to be rotated a bit to resemble more like a neck/middle/bridge thing, visually)

Anyway, to implement switchable OMG we just need to insert the OMG cap in the shunt path, actually two individual (and likely different) caps for each coil could be used, even combined with resistors for more subtle effect. Then a push-pull pot could short out these series elements. There are many possibilities...

That’s awesome George. Thanks for sharing this. It’s nice when we get the whole bass group adding their knowledge to these posts.

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Re: Making a Tribute L-2000 an L-2000 Plus

Postby Paul Gagon » Wed Oct 24, 2018 4:34 pm

b17krk wrote:Thank you Paul, I really appreciate you taking the time to help out. You are a true gent!


OK Kirk, here’s what I did. I modified the L-2000 Plus circuit so as to not add any extra holes to the bass. What you will be doing is replacing the current pickup coil configuration switch (4PDT) with a DPDT on/on/on switch. That’s the switch above the Treble control. Next, you will be replacing the volume control (250KA) with a 250KA pot that has a DPDT pull switch attached to it.

Basically you will be re-wiring the passive/preamp control switch to be the bridge pickup coil configuration switch. The preamp control option will now move to the pull switch on the volume control, more on that later. Hopefully this wiring diagram will be clear enough to do the entire mod without any issues. If you run across any problems, let me know. Anyway, here it is.

Image

As you look through this diagram you’ll see an asterisk by the Red wire from the preamp and a connection I labeled “A” off the pull switch on the Volume control. I wanted to add some notes to the drawing but it just took too much room so I’ll put the notes here in the document.

Notes: The pull switch on the Volume control has 2 positions. The bass is operating in passive mode when the Volume control knob is pushed down. To go into Preamp mode, you simply pull up on the volume knob. In preamp mode, the preamp is not in the Treble Boost mode unless the Red wire from the circuit board is connected to “A”. If you tie the Red wire off and leave it isolated, the bass is only in the Preamp On mode. If you wanted to have the preamp on with Treble Boost, you would simply connect the Red wire from the preamp board to the switch connection labeled “A”. Now, if you wanted to have a little Treble Boosting when you activated the preamp, you would connect the Red wire to the “A” connection through a resistor. In other words, you would solder the Red wire to one leg of a resistor and tie the other leg of the resistor to connection “A”. The larger the value of resistor, the less Treble Boost you will have. A resistor value of around 1K would give you a pretty good boost while a value of 100K would be pretty mild. Experiment around and see what resistance value you like.

So, there you have it. An L-2000 Plus without drilling a hole in your bass. Keep us all up to date on your adventure with the mod. And again, thanks for being willing to explore.

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Re: Making a Tribute L-2000 an L-2000 Plus

Postby b17krk » Thu Oct 25, 2018 2:12 am

Wow, this is awesome stuff, thank you so much Paul!

Regarding the note about the Treble Boost option, I have recently upgraded the original v1.2 preamp to a USA v1.3, which was shipped overseas directly from the G&L online store. In doing so, I removed the original 10k resistor previously wired "in-line" between the active/passive switch and "SW" on the v1.2 preamp - mainly because I was under the impression that it had since been incorporated into the v1.3 preamp as R11. Was I right to do this, and if so, will I still need to connect the Red wire to the "A" connection through an additional resistor in order to achieve a little treble boost?
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Re: Making a Tribute L-2000 an L-2000 Plus

Postby Paul Gagon » Thu Oct 25, 2018 5:22 am

b17krk wrote:Wow, this is awesome stuff, thank you so much Paul!

Regarding the note about the Treble Boost option, I have recently upgraded the original v1.2 preamp to a USA v1.3, which was shipped overseas directly from the G&L online store. In doing so, I removed the original 10k resistor previously wired "in-line" between the active/passive switch and "SW" on the v1.2 preamp - mainly because I was under the impression that it had since been incorporated into the v1.3 preamp as R11. Was I right to do this, and if so, will I still need to connect the Red wire to the "A" connection through an additional resistor in order to achieve a little treble boost?


Hi Kirk,

Yes, you were right to remove the in line 10K resistor as it is now on the PCB as R11. Also, you will still need to connect the Red wire from the preamp board to connection “A” to achieve treble boosting. Have fun with the mod and report back on how it’s going.

Paul
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Re: Making a Tribute L-2000 an L-2000 Plus

Postby b17krk » Mon Dec 17, 2018 9:05 am

Okay, so I finally found a bit (quite a lot actually) of time to have a go at this, and bearing in mind how inexperienced I am when it comes to modding, I seem to have completed it with mixed success!

On the plus side I managed to order the correct switch and capacitor/resistor values - and even managed to remove the existing components safely and cleanly. I re-wired it exactly as shown in the diagram and the cavity now looks incredibly neat and tidy - a far cry from how it originally looked! And the tones that now ring out from it are awesome!

Now for the negatives!

The bass buzzes (a lot) when touching the strings, pots, switches and bridge - which from what I've read (on here and elsewhere) is a sure sign that somewhere in the circuit is a grounding issue. I have checked, double checked and triple checked the grounding wires connecting the backs of the pots, the jack and the bridge ground with a multi-meter and there appears to be continuity, so I'm now at a loss as to what to try next.

I have to own up and admit that during this process I did have an issue with soldering the grounds to the back of the pots, in that I may have applied more heat than was necessary (and possibly for longer than necessary also) causing the backs of the bass and treble pots to loosen. They still function correctly in that the bass pot "cuts" the bass and the treble pot "cuts" the treble, but would this be enough to completely screw up the grounding?

I appreciate how difficult it is to diagnose any issue like this without having the bass in front of you, but if it sounds like a problem that anybody may have experienced themselves in the past then I'd be extremely grateful for your input.
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Re: Making a Tribute L-2000 an L-2000 Plus

Postby deltafred » Mon Dec 17, 2018 11:02 am

Kirk

On my L-2500 Tribute I had the pot back that all the grounds are soldered to not making contact with the pot body. It gave me all sorts of hum/buzz and had me scratching my head for a while because I could see it should have been connected but my multimeter said differently.

I soldered an extra ground wire on the back which I wrapped around the pot mounting thread and trapped between it and the cavity screening paint. I also connected all the pot backs together electrically "just in case".

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Re: Making a Tribute L-2000 an L-2000 Plus

Postby Paul Gagon » Mon Dec 17, 2018 10:05 pm

Hey Kirk,

That absolutely sounds like a grounding issue. I’m glad you did a bit of detective work with an ohm meter. This might sound redundant, but if you have time, would you mind doing another continuity test? Plug in your instrument cable to the bass and do a continuity test from the ground of the plug end that would normally go into your amp, and the bridge of the bass. Also, check the continuity from the ground on the plug to the pots and switches. Basically your testing your cable and your bass grounding. If you have under 1 or 2 ohms you’re grounding is good.

Question, have you tried this same noise test with another bass? Using the same cable and amp? I’m just trying to isolate things as much as possible. I’ve never had a bass hum/noise get louder when touching the bridge, strings, pots or switches when all these were properly grounded and connected to an amplifier through a good cable. If only this bass has a problem then we need to go deeper.

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