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Hello all,

A customer dropped a recent American Professional II Strat to have a Double-tap humbucker installed at the bridge. I rewired the guitar following Fender's schematic (see below) and installed a stacked 250 and 500k volume pot, treble bleed PCBs and push-push coil split/tap for this pickup. All went very well, until I tried it at switch position 2. Sure enough, the new unit does not play well with the others and combining delivers the most nasal noise you ever heard. Now after some searching, I found out it seems over the years Fender made two versions of this pickup, with, you guessed it, reversed polarity and/or wind direction. The current version hates what's already living into the guitar.

As a fast fix, I tried reversing the middle pickup's wires (knowing I'd run into problems with pos. 3 but hey). Worked like a charm until I activated the coil split, where it was back to nasal city. Then I tried it the other way round, reversing ground and hot on the humbucker, which, interestingly enough yielded no sound at all. Must have something to do with the coil tap, but I'm no Gerry Hayes so forgive me for not quite understanding why TF.

Now if somebody has run into the same problem with this very peculiar pickup, please help me. I might get into mapping the pickup's properties as per Gerry’s excellent book but I fear I won't get this to work properly as I suspect the pickup has to be installed exactly as intended for the coil tap/split option to be working.

Maybe Gerry could chime in…

Here's what I've found so far.

Fender’s schematic :

https://www.fmicassets.com/Damroot/Original/10001/SM_011391XXXX_Am_Pro_II_Stratocaster_HSS.pdf

Gombrelli's comments on how the thing’s working

https://stratocasterdesign.com/index.php/wiring-a-double-tap-humbucker/

And then Fender's specs for the same pickup in the American Performer… see that polarity is reversed at the end of both Fender spec sheets.

To my asking for technical advice, Fender just replied "see an authorized service center" and offered me to become one. No thanks.