J Mascis Jazzmaster mods

The Squier by Fender J Mascis Jazzmaster is a totally decent guitar for about $450.  I recently purchased one because I especially liked the neck, cool anodized aluminum pickguard, and adjusto-matic bridge.  As with any new guitar, I have to upgrade it as soon as I get it, and I felt the electronics were especially lacking in this one.  The pickups are basically P-90s under a Jazzmaster cover and are too hot and dark for my taste.  The neck measured 8.2K and the bridge 8.6K.  I have never liked the upper controls on the Jazzmaster, so I'll be putting a series/parallel switch in there and using the rollers as master treble and bass bleed.  

my Vintage Copperhead Jazzmaster pickups

For this mod you will need:

(2) Schuyler Dean Pickups Vintage Copperhead (neck and bridge)
(1) 1M mini reverse audio taper pot (for the bass rolloff)
(1) 1M mini audio taper pot for the treble rolloff (you can reuse the one from the master tone)
(2) CTS 1M split-shaft audio taper pots (neck and bridge volume)
(1) Switchcraft jack
(1) .001 uF cap (bass rolloff)
(1) .022 - .047 uF cap (treble rolloff)
(2) .001 uF caps wired parallel to (2) 150K resistors (volume mod)
(1) wiring diagram.  I used a Rothstein Guitars diagram for this mod.  

Above is an example of an audio taper pot (A1M) vs. a linear (B1M) pot.  All of the pots we will be using for this mod will be audio taper.  

Begin by removing the strings, bridge, and posts (it helps to remember how high the posts are when you remove them so you can set the action again later).  Remove the pickguard and pickups, unsolder the two ground wires from the back of the pot.  Before you set the guitar aside, use some copper tape to provide a better ground between the shielding paint and the pickguard like I did here:

Remove all the old parts and install new parts including pickups.  As you are assembling the guitar, plug in an amp and tap on the pickups to check your wiring.  You don't want to get the strings on and then realize that you missed something and have to take it all apart again like I did!  

Install an extra piece of foam under each pickup for extra height adjustment.  My vintage-style pickups are a bit thinner than the stock ones, plus the neck angle is a bit different on this Jazzmaster to make room for the Adjusto-matic bridge.  With the strings at tension, depress the outside strings at the last fret.  You want to get the bridge pickup within 1/16" of the strings on the bridge pickup and 1/8" on the neck pickup.  

When assembling the bridge, use a small screwdriver to bend notches in the spring holding the intonation screws in place, this will make for a tighter functioning bridge.

See the full video on YouTube for the before, during, and after of this build: