OK, I fixed the "reverse pan pot syndrome" (aka RPPS) that seems to plague some, but curiously not all, older Carvin LB series basses. It was actually very simple to figure out why the p'ups were reversed and what I needed to do to rectify the problem, at least on my bass. I have the older LB75 which I bought in either '92 or '93. This bass has the 4 knobs on it with the preamp that has two stacked boards connected together with several black wires.
Locate the two shielded, two conductor wires that come into the control cavity from each p'up...on the end, you'll see a shield with heatshrink on each one and a black and red wire as well on each p'up wire.
With the guitar on it's face (on a soft cloth like a towel), the neck to your left and the preamp boards exposed, the board furthest from you has those wires going to it (this circuit board has the volume and pan pot soldered to it). Mine had the bridge p'up wire going to solder pads on the left end of the board and the neck p'up wire was going to some pads about 1/2 way down the length of the board to the right. All these pads are right on the top edge of the circuit board.
This will take some careful soldering. The wires (on mine) were left to right...shield-black-red.
Carefully remove the wires (read:
fragile wires) from the circuit board by unsoldering them and using solder wick (you can get this at Radio Shack), clean the solder off the pads, both sides of the circuit board.
Be very careful...you don't want to remove the pads. These circuit boards don't seem to be very beefy so you want to be very careful....Did I say you have to be careful? If you remove the pads it's big time suck city
Once you have all the solder cleaned out of all six holes, it's time to reinstall the wire from the p'ups correctly.
On mine, I installed and soldered the wires from the bridge p'up to the left most three holes and the neck p'up wires to the three holes that were halfway down on the circuit board. Check your work, making sure you don't have any solder bridges, easy to do as tight as it is in there if you're not practiced up on soldering.
While I was in there, I cleaned the pots with Caig D5 pot cleaner as some were getting a tad scratchy.
Lay the wires you had to move in the cavity as neatly as you can making sure you don't stress any solder joints and lay the cavity cover on and screw it down (don't pinch any wires).
Plug in your bass and check your work....when you rotate the pan pot CW, your neck p'up should be soloed, and when you spin it CCW, your bridge p'up should be soloed.
This is easy to check...with one p'up soloed and the bass plugged into your amp, tap the p'ups with a screwdriver (or something else ferrous)...you'll hear a loud tapping on the active/soloed p'up and practically nothing on the other. Spin the pan pot the other way and check that the other p'up is active and the previously checked p'up is inactive....
Easy peasy
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If you don't feel adequate to the job, please ask a qualified technician to do it for you. I did mine in less than a half hour so to have a tech do it that knows what he or she is doing would be far better than trashing your wonderful Carvin and should be able to be done for not alot of money (you know, the whole "peace of mind" thing?). I am not responsible if you decide to go it alone without the necessary experience and bring ruination upon your preamp board*********