Installing Standard Humbucker in TrueDuo Circuit
Sorry if this has been covered, but I could find no info on how to do this, so here's how.
Some of you may not know that the TrueDuo humbucker is a three coil pickup. One side of the humbucker has a coil underneath it that, when the coil tap on the vol is activated, makes a stacked humbucker for hum-cancelled single coil tone. When the bridge pickup is used in conjunction with the middle single coil, it is turned into a true single coil to maintain hum-cancellation. The wiring to do this is fairly complicated, and I'm not going to describe it as most folks will just want to know how to put in a standard humbucker. This complex wiring could have been avoided if Ibanez would have just used a stacked humbucker in the middle position, but they didn't.
My customer brought in a Carvin M22 4-cond pickup to put in the bridge position of his sv5470a J-Craft. I took meter readings of the TrueDuo pup that were odd, so I disassembled the pickup and found that they had spliced some wires under heatshrink. Long story short, my customer and I decided to make the Carvin pickup split when the vol pot was lifted and also when the 5-way switch activated it with the middle pickup to maintain hum-cancellation.
This was accomplished by removing all the wires on the bridge pup side of the push/pull - two orange wires, one green wire and the pickup wires - and they were also removed from the 5-way. The bridge side of the push/pull was then used as a standard coil tap, with the tap wire of the pickup going to the center lug and the top lug going to ground. The hot wire of the pickup then went to the lug on the 5-way that previously held the green wire and the ground was grounded on the pot shell.
In order to get the bridge pickup to tap automatically when used with the middle pickup, there must be a coil tap activated by the 5-way. I used the terminals previously used by the orange wires for this. Wire a jumper from the tap location on the push/pull center lug to the lug where one of the orange wires were. Then ground the lug where the other orange wire was. This will send the tap to ground when the 5-way is in the #2 position.
It's a simple wiring setup when you know what the original pickups are doing, but it was pretty time consuming to figure out. Hope this helps someone out.