Hi: I'm sorry it took so long...I'd not checked my profile in months.
Assuming you haven't already replaced the wiring, and assuming you want to restore the standard configuration, I'd basically pull out everything and start over.
Any pickups you buy will have wiring diagrams. A lot of different ones are posted at www.stewmac.com. I'm not an experimenter with sounds: I play almost all the time on the front pickup and and adjust the volume and tone a little from song to song. If you're more adventurous, you might consider more elaborate wiring than standard (obviously, that's what your Epi's previous owner thought).
I installed Seymour Duncan humbuckers on my Sheraton II, and I wrote up a treatise on how I did it, which I will cut and paste below. A few thoughts: I like Seymour Duncans because the web site has sound clips of the various models offered. I don't live in a big city (no GC within over 100 miles) so that's important when I'm dissatisfied with the standard pickups; I have heard good things about GFS humbuckers, but no direct experience. The pickups I put in the Sheraton II were "Anniversary" models, which were a package of a Jazz neck pickup and a JB bridge. They had nickel covers, which I wanted for the looks, as well. I later bought a Gibson ES-335, which made the Sheraton surplus to requirements, and I traded it off...had I kept it, I would have eventually gone with Gibson '57s, which are in my 335.
Back to your guitar: the issue, to me, would be whether any new holes were drilled in the guitar. If they used the stacked knobs to avoid new holes, God bless 'em. If the guitar has additional holes, you may want to think about adding a feature or two to fill them up -- holes on the face of a guitar can be difficult to hide, due to the necessity of refinishing and so on.
If no new holes were drilled, it's simply a matter of replacing the specialized controls with more conventional ones. An alternative, by the way, is to buy a harness from Mojo Assemblies http://www.mojomusicalsupply.com/item.asp?pid=577858&pg=92721&id=2115110; you should be able to install it in the 335 without the problems I had with the Sheraton due to the bound -- and very narrow -- f-holes.
Anyhow, here's my treatise:
I got my '95 Sheraton II last summer and immediately decided it needed better pickups, so I ordered the Seymour Duncan "Silver" set (Jazz neck, JB bridge) from MF. Then I was confronted with the problem of installing them. My local tech turned down the job!
Apparently Sheratons are not all the same. Mine was made at the Samick factory in Korea, and has small f-holes and no access route through the pickup cavities. Gibson ES-335s and maybe some other Sheratons do, and that makes life easier.
Here's what I did: the Mojo Assemblies pots are too big to fit through the opening of the f-hole, which on mine is 1" x .75" at its largest. That part of the f-hole is any where from 2" to 8" away from the various components, so that has to be kept in mind when cutting the wiring to length.
I stole the idea from Mojo of using a template, which I made from a piece of cardboard and a set of leather punches. I measured the distances to all the controls, and punched holes for them in the same relative position on the cardboard as on the guitar top.
My Epi had one noisy pot and a noisy switch, so I ordered new "mini" pots from Stewart-McDonald (part # 3477) along with a three-way switch (#1217), an output jack (#4652) and two of their basic wiring packages (#4575), which include .020 and .050 caps for the tone controls. It took most of both wiring kits for the Epiphone, so don't scrimp.
The Seymour Duncans came with a wiring diagram, as did the three-way switch, and both offer different options. I chose to wire them up as conventional humbuckers and to wire the switch to allow using the volume controls to blend the pickups when using both -- don't worry, it's all in the diagrams.
I put the new pots, switch and jack in the template from the bottom so they'd lay out like the real ones from the top, and then wired them from the bottom side. I used a Sharpie to label the holes on the underside. Very easy to keep track of that way.
You'll probably need to roughen the surface of the pot body where you solder the grounds in order for the solder to stick. Another tip: turn the shafts on the pots all the counterclockwise (off) to avoid damaging them from heat.
The .020 cap goes on the bridge tone control and the .050 on the neck pot. This emulates Gibson wiring, which uses .022 and .047 values, respectively. Before you solder the cap leg to the pot body, put an alligator clip on to act as a heat sink so you don't fry it with the soldering iron.
Solder up everything but the wires from the pickups, and make sure all the parts share a ground by checking with a multimeter. Otherwise you'll put it together and get a nice hum and have to take it all apart again. Trust me -- I know.
Use the shielded wire between the switch and the output jack, and between the volume and tone pots. Since I actually disemboweled my Epi before I got this far, I used the sleeves provided in the original harness to dress all the wires before soldering. Always allow a bit of slack for the shield wire to reach to the back of the pot, where you'll be soldering it to ground.
The SD pickups have 5 wires coming out of them: red, white, green, black and silver (bare). Strip the ends of the red and white wires, twist them together and secure the join with solder, then put heat shrink tubing over the bare part to insulate them. The leads were a little too short for comfort, so I soldered the green and bare wires together (they both go to ground, you're not shorting out anything) and spliced in a 5" length of the white wire to them, covering all the joints with heat shrink. Then I spliced another 5" to the black wire and covered the joint with heat shrink; I repeated this operation for the second pickup.
Note that other brands have different color coding, but the principal doesn't change. In my experience, all pickup makers provide full wiring diagrams, and Stewart-McDonald has others at their website.
When I was done I had two leads from each pickup, a white to connect to ground and a black to connect to hot.
Time to work on the Sheraton: set her on a towel on your workbench with the peghead to your right (reverse for a lefty), loosen the strings enough to work the stop tailpiece off its studs, and lay it down on the other side of the neck from you. If you're going to restring anyway, just go ahead and take the strings off.
Take an ice cube tray (if your refrigerator doesn't have one, dollar stores do) and lay it behind the guitar where you won't be knocking it over. This is where you'll keep the screws and washers and springs and other little gubbinses organized.
Wrap a cloth under the edge of each knob and lift: it will pull right off. Occasionally you'll find one that needs more persuasion, but be wary of using screwdrivers or other tools, because it's really easy for it to slip and mar the top. When possible I put something between the tool and the top to minimize dings.
The switch knob unscrews (you were wondering why it didn't pull right off!). Then undo the nuts on the various controls and push them down through the holes in the guitar top. Take out the screws holding the pickup rings and lift out the pickups from their cavities, clip the leads that go into the guitar interior (I enjoy that part), and disassemble the pickups from their rings, being careful not to lose the springs -- even though the new ones come with springs, it's easier than you might think to watch them arc up into the air and drop behind some unmovable object.
Using a thin, bent wire (a large paper clip that's been straightened out except for one loop is perfect) fish the wires inside the body out through the f-hole and pull the controls out. It might be imprudent at this point to start snipping wires, because you want everything to come out with a minimum of fuss.
Identify the wire coming from the tailpiece or bridge: this is the string ground, and you'll be soldering it into the circuit later.
Then attach the pickups to the rings. Note that the thin ring is the neck pickup, and the narrower end is against the fingerboard, and that the pole pieces on the pickups are also next to the neck. The thick ring is for the bridge, and the thicker end -- and the pole pieces -- are toward the bridge. Pickup springs are devils without any horns, let me tell you. What I do is put the pickup in the ring, and run the screw on one side to the flange on the side of the pickup where it screws in. That makes it easier to put the other screw in place, put its spring around it, and compress the whole assembly while screwing that side in. Then you repeat the fun for the other side, and maybe 2-3 hours later, you've got the spring mounted nicely between the rings and the flanges. It's useful to make sure the floor underneath the workbench is clear of obstruction for the many times you'll be on your hands and knees, retrieving the springs. If somebody knows an easier way, feel free to chime in!
Finally, solder the pickup leads to the harness. You may have to remove the harness from the template for this step. If so, be sure to have a protective cover over the guitar top to avoid boogers in your finish.
Now we're at the fun and games stage of the whole catastrophe. Take a length of string long enough to reach from the wide part of the f-hole to the output jack, allow a few more inches, and tie one end so that you can pull it up into the hole. Using the bent paper clip,
fish the string from inside the guitar up through the jack hole in the guitar body (mine required two steps: fishing to the neck tone hole, then from there to the output hole, because my paper clip wasn't long enough. That's the only time I had to do that). Pull the jack up into the hole (a thin jeweler's screwdriver is useful in persuading it to come up straight); grip the end of the jack securely with your fingers or needlenose pliers while you cut the string as far inside the jack as you can, then install the flat washer and nut. Damn, that sounds easy...but if it doesn't work right away, try, try again. Pretty soon -- after a day or so -- you'll get good at it!
Then do each pot in turn (I started with the one closest to the jack, and worked my way up), remembering to put a star washer on the shaft of the pot before you tie the string on. Patience, patience, patience. As soon as each pot is sticking its lovely little shaft straight up in its hole, untie the string and pull it out, never letting go of the pot. You will likely have to drop the pot down a fraction of an inch in order to pull out the end of the string, but maybe you'll get lucky, or have better knot-tying skills than I do: I always seem to end up with a bit of a tail past the knot.
The switch is the last to go in, and then you are done with that part. Take up the slack in the leads coming from the pickups and fold them into the pickup cavity. This is a chance to make it look perhaps a little more professional. Attach the pickups and string it up (or, replace the tailpiece and tune it up). Leave the knobs off until you've had a chance to test your work. I plug into a tuner and make sure the tuner recognizes the notes from each switch position...then I plug into an amp for the final test before I put the knobs back on.
Have fun and good luck...and avoid telephone hookup wire: it's solid core and the solder joints break easily while you're working everything into place. Guess how I know that?
Assuming you haven't already replaced the wiring, and assuming you want to restore the standard configuration, I'd basically pull out everything and start over.
Any pickups you buy will have wiring diagrams. A lot of different ones are posted at www.stewmac.com. I'm not an experimenter with sounds: I play almost all the time on the front pickup and and adjust the volume and tone a little from song to song. If you're more adventurous, you might consider more elaborate wiring than standard (obviously, that's what your Epi's previous owner thought).
I installed Seymour Duncan humbuckers on my Sheraton II, and I wrote up a treatise on how I did it, which I will cut and paste below. A few thoughts: I like Seymour Duncans because the web site has sound clips of the various models offered. I don't live in a big city (no GC within over 100 miles) so that's important when I'm dissatisfied with the standard pickups; I have heard good things about GFS humbuckers, but no direct experience. The pickups I put in the Sheraton II were "Anniversary" models, which were a package of a Jazz neck pickup and a JB bridge. They had nickel covers, which I wanted for the looks, as well. I later bought a Gibson ES-335, which made the Sheraton surplus to requirements, and I traded it off...had I kept it, I would have eventually gone with Gibson '57s, which are in my 335.
Back to your guitar: the issue, to me, would be whether any new holes were drilled in the guitar. If they used the stacked knobs to avoid new holes, God bless 'em. If the guitar has additional holes, you may want to think about adding a feature or two to fill them up -- holes on the face of a guitar can be difficult to hide, due to the necessity of refinishing and so on.
If no new holes were drilled, it's simply a matter of replacing the specialized controls with more conventional ones. An alternative, by the way, is to buy a harness from Mojo Assemblies http://www.mojomusicalsupply.com/item.asp?pid=577858&pg=92721&id=2115110; you should be able to install it in the 335 without the problems I had with the Sheraton due to the bound -- and very narrow -- f-holes.
Anyhow, here's my treatise:
I got my '95 Sheraton II last summer and immediately decided it needed better pickups, so I ordered the Seymour Duncan "Silver" set (Jazz neck, JB bridge) from MF. Then I was confronted with the problem of installing them. My local tech turned down the job!
Apparently Sheratons are not all the same. Mine was made at the Samick factory in Korea, and has small f-holes and no access route through the pickup cavities. Gibson ES-335s and maybe some other Sheratons do, and that makes life easier.
Here's what I did: the Mojo Assemblies pots are too big to fit through the opening of the f-hole, which on mine is 1" x .75" at its largest. That part of the f-hole is any where from 2" to 8" away from the various components, so that has to be kept in mind when cutting the wiring to length.
I stole the idea from Mojo of using a template, which I made from a piece of cardboard and a set of leather punches. I measured the distances to all the controls, and punched holes for them in the same relative position on the cardboard as on the guitar top.
My Epi had one noisy pot and a noisy switch, so I ordered new "mini" pots from Stewart-McDonald (part # 3477) along with a three-way switch (#1217), an output jack (#4652) and two of their basic wiring packages (#4575), which include .020 and .050 caps for the tone controls. It took most of both wiring kits for the Epiphone, so don't scrimp.
The Seymour Duncans came with a wiring diagram, as did the three-way switch, and both offer different options. I chose to wire them up as conventional humbuckers and to wire the switch to allow using the volume controls to blend the pickups when using both -- don't worry, it's all in the diagrams.
I put the new pots, switch and jack in the template from the bottom so they'd lay out like the real ones from the top, and then wired them from the bottom side. I used a Sharpie to label the holes on the underside. Very easy to keep track of that way.
You'll probably need to roughen the surface of the pot body where you solder the grounds in order for the solder to stick. Another tip: turn the shafts on the pots all the counterclockwise (off) to avoid damaging them from heat.
The .020 cap goes on the bridge tone control and the .050 on the neck pot. This emulates Gibson wiring, which uses .022 and .047 values, respectively. Before you solder the cap leg to the pot body, put an alligator clip on to act as a heat sink so you don't fry it with the soldering iron.
Solder up everything but the wires from the pickups, and make sure all the parts share a ground by checking with a multimeter. Otherwise you'll put it together and get a nice hum and have to take it all apart again. Trust me -- I know.
Use the shielded wire between the switch and the output jack, and between the volume and tone pots. Since I actually disemboweled my Epi before I got this far, I used the sleeves provided in the original harness to dress all the wires before soldering. Always allow a bit of slack for the shield wire to reach to the back of the pot, where you'll be soldering it to ground.
The SD pickups have 5 wires coming out of them: red, white, green, black and silver (bare). Strip the ends of the red and white wires, twist them together and secure the join with solder, then put heat shrink tubing over the bare part to insulate them. The leads were a little too short for comfort, so I soldered the green and bare wires together (they both go to ground, you're not shorting out anything) and spliced in a 5" length of the white wire to them, covering all the joints with heat shrink. Then I spliced another 5" to the black wire and covered the joint with heat shrink; I repeated this operation for the second pickup.
Note that other brands have different color coding, but the principal doesn't change. In my experience, all pickup makers provide full wiring diagrams, and Stewart-McDonald has others at their website.
When I was done I had two leads from each pickup, a white to connect to ground and a black to connect to hot.
Time to work on the Sheraton: set her on a towel on your workbench with the peghead to your right (reverse for a lefty), loosen the strings enough to work the stop tailpiece off its studs, and lay it down on the other side of the neck from you. If you're going to restring anyway, just go ahead and take the strings off.
Take an ice cube tray (if your refrigerator doesn't have one, dollar stores do) and lay it behind the guitar where you won't be knocking it over. This is where you'll keep the screws and washers and springs and other little gubbinses organized.
Wrap a cloth under the edge of each knob and lift: it will pull right off. Occasionally you'll find one that needs more persuasion, but be wary of using screwdrivers or other tools, because it's really easy for it to slip and mar the top. When possible I put something between the tool and the top to minimize dings.
The switch knob unscrews (you were wondering why it didn't pull right off!). Then undo the nuts on the various controls and push them down through the holes in the guitar top. Take out the screws holding the pickup rings and lift out the pickups from their cavities, clip the leads that go into the guitar interior (I enjoy that part), and disassemble the pickups from their rings, being careful not to lose the springs -- even though the new ones come with springs, it's easier than you might think to watch them arc up into the air and drop behind some unmovable object.
Using a thin, bent wire (a large paper clip that's been straightened out except for one loop is perfect) fish the wires inside the body out through the f-hole and pull the controls out. It might be imprudent at this point to start snipping wires, because you want everything to come out with a minimum of fuss.
Identify the wire coming from the tailpiece or bridge: this is the string ground, and you'll be soldering it into the circuit later.
Then attach the pickups to the rings. Note that the thin ring is the neck pickup, and the narrower end is against the fingerboard, and that the pole pieces on the pickups are also next to the neck. The thick ring is for the bridge, and the thicker end -- and the pole pieces -- are toward the bridge. Pickup springs are devils without any horns, let me tell you. What I do is put the pickup in the ring, and run the screw on one side to the flange on the side of the pickup where it screws in. That makes it easier to put the other screw in place, put its spring around it, and compress the whole assembly while screwing that side in. Then you repeat the fun for the other side, and maybe 2-3 hours later, you've got the spring mounted nicely between the rings and the flanges. It's useful to make sure the floor underneath the workbench is clear of obstruction for the many times you'll be on your hands and knees, retrieving the springs. If somebody knows an easier way, feel free to chime in!
Finally, solder the pickup leads to the harness. You may have to remove the harness from the template for this step. If so, be sure to have a protective cover over the guitar top to avoid boogers in your finish.
Now we're at the fun and games stage of the whole catastrophe. Take a length of string long enough to reach from the wide part of the f-hole to the output jack, allow a few more inches, and tie one end so that you can pull it up into the hole. Using the bent paper clip,
fish the string from inside the guitar up through the jack hole in the guitar body (mine required two steps: fishing to the neck tone hole, then from there to the output hole, because my paper clip wasn't long enough. That's the only time I had to do that). Pull the jack up into the hole (a thin jeweler's screwdriver is useful in persuading it to come up straight); grip the end of the jack securely with your fingers or needlenose pliers while you cut the string as far inside the jack as you can, then install the flat washer and nut. Damn, that sounds easy...but if it doesn't work right away, try, try again. Pretty soon -- after a day or so -- you'll get good at it!
Then do each pot in turn (I started with the one closest to the jack, and worked my way up), remembering to put a star washer on the shaft of the pot before you tie the string on. Patience, patience, patience. As soon as each pot is sticking its lovely little shaft straight up in its hole, untie the string and pull it out, never letting go of the pot. You will likely have to drop the pot down a fraction of an inch in order to pull out the end of the string, but maybe you'll get lucky, or have better knot-tying skills than I do: I always seem to end up with a bit of a tail past the knot.
The switch is the last to go in, and then you are done with that part. Take up the slack in the leads coming from the pickups and fold them into the pickup cavity. This is a chance to make it look perhaps a little more professional. Attach the pickups and string it up (or, replace the tailpiece and tune it up). Leave the knobs off until you've had a chance to test your work. I plug into a tuner and make sure the tuner recognizes the notes from each switch position...then I plug into an amp for the final test before I put the knobs back on.
Have fun and good luck...and avoid telephone hookup wire: it's solid core and the solder joints break easily while you're working everything into place. Guess how I know that?