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Fender Double-tap humbucker problem
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Fender Double-tap humbucker problem
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.
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9 Replies
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Here are the differences between the two wiring schemes. Looks like Fender likes to play with polarities and you just have to know what’s in your guitar before you buy. Of course the customer’s guitar is :
Neck = South
Mid = North
With a new hum bucker that’s as follows :
Bridge = South
North (active when split/tapped so trouble ahead already)
Don’t know yet how the coils are wound.
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Hey Pierre, fender humbucker pickup is not so friendly to mod, this pickup has a coil extended to make this tap thing, its not so easy to rewired, and terminals on the pickup not accept heat, if you touch with the solder iron, plastic melts and force the terminal up, and this will break the coil (ask me how i know that! Not fun at all)
Look like its magnetic problem, reversing the magnet on bridge pickup will make this in phase with original middle pickup, solving H + S on 2 position, and when tap a bobin you have one bobbin with (north ou south) engaged, if you flip the magnet everything is in phase.
We need reverse wound and reverse polarity to had everything in phase and no hum. I believe when you change the middle pickup wire, its in phase, but with reverse polarity.
So, the easy way is! Rewire the middle pickup to original ground and hot. In the bridge pickup, remove the baseplate and flip the magnetic bar of bridge pick-up to get everything in phase, just mark one side of the magnet with a arrow up, remove the screws of base plate, apply some heat to melt the paraffin wax and rotate the magnet (bar magnets have poles in the sides, so, arrow down to reverse de magnet).
If cancel hum in 2 position with tap on, everything is in phase.
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Thanks Lin,
I have come to the same conclusion. I’m not ready to risk ruining this ultra-fragile and very strange pickup by prying it even slightly apart to flip the magnet as I would with any normal humbucker, though. I guess I’ll have to give up on it and recommend that the customer gets compatible mid and neck units. Bloody shame, I know. Thanks for taking the time, big thumbs-up.
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Hey Pierre! Its not a complicated process, chances to snap a wire are very low (wire from fender pickup humbucker goes directly to terminals, no “pig tail”. It’s 4 screws out, heat from a blow dryer and everything come a part!
Try in a few dead or not so expensive pickups before, it’s a huge gain for your shop and clients stay very happy!
Know your limits is always a great and positive thing too!
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Hey Lin,
I’ve done this very often, as well as taking coils apart and reassembling the pickups, so I’m no stranger to the process. This particular pickup is not our garden-variety humbucker though, and as I’ve been warned by a colleague about its peculiarities and extreme fragility I have chosen not to mess with it.
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One last thing I would try would be swapping the middle and neck pickups. Worth a try.
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Hey Jon,
I’ve thought about doing exactly this. Problem is those two pickups happen to not be the same, they are formulated for their respective positions so we’d end up with too much output at the neck and a weaker mid. I might give it a try, though. Not sure the customer would love to have his sound changed.
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Understood. Plus the pole spacing is slightly different also. Just tossing out troubleshooting ideas.
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I’ve discussed this with the customer and he’s not going for it. He loves his present tones from the mid and neck and would rather ditch the Double-tap and go for a JB instead. I totally get it.
Thanks for helping!
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