CIJ Fender Mustang: electronic mods

The below noisy Mustang was entrusted to me for clean up. Enormous buzz when the volume was all the way down was a main ball breaker. As usual the guitar was only played with volume and tone all the way open by the owner, which indicated familiar 'cheap F' problems - though it has some 'F top of the line' features too. Strange mix.




The following modifications were decided upon:
a) star grounding
b) shielding
c) other pickups
d) alternative switching
e) treble bleed cap
f) a 0,022uF cap instead of the stock 0,047uF
g) lowering the height of the switches so as to stop scratches your palms



a) Star Grounding

Much noise is to be had from bad ground wiring. However little effort it takes the big guitar manufacturing company's doesn't to bother soldering 2 more wires to make your guitar humfree. All the points that should connect to ground are brought together at a star (center point) and then this point is connected to the ground tab of the jack plug.
In the stock setup as you can see everything is grounded through pot casings and the control plate. The ground tab of the jack plug is not even connected -- though it does connect through the case to the control plate, off course





b) Shielding

Further noise can be reduced by shielding the body cavity and pickguard of the guitar. To my surprise, the back of the pickguard was already coated with aluminum foil and the body cavities touched upon with coductive paint. This doesn't make for a good enough shield -- it should be continously conductive.


conductive paint in the body cavity



shielded pickguard, stock wiring



bare guitar, covered in masking tape. after this, the masking tape is cut out where the body cavity is and spray glue can be applied to the body cavities. Check the other entries for more details on shielding.





Screwed down tremelo wire, now attached to the shield



c) Pickups

Although this Mustang had unstaggered Strat pickups on them, I am going to change them for less hot, more vintage sounding staggered alnico's; Luckily I have a spare lefty stagger I can use, because if you use Strat pickups, remember the bridge pickup is upside down. If your pickup not so hot, you might be able to increase to volume on your amp a bit, hence more headroom, clearer sound, you name it.





d) Alternative switching

Together with the new pickups came the improved Seymour Duncan Mustang wiring scheme.

http://www.jag-stang.com/MustangHtml/Images/GMArtsModSchematic.gif

Stock Wiring:

Switch 1 N Pickup on in Phase - N Pickup Off - N Pickup out of Phase
Switch 2 B Pickup on in Phase - B Pickup Off - B Pickup out of Phase

New Wiring:

Switch 1 N Pickup On - N and B in parallel - B Pickup On
Switch 2 Controls Bypassed - Volume Only - Controls Active



The problem was that this requires a lot of wires to run from the switches on top down the bridge pickup cavity through the hole (it fitted thank god) to the pots.





e) treble bleed cap and f) a 0,022uF cap instead of the stock 0,047uF

John Hewitt explained me the precise functionings of the little cap that make you not lose trebles when you turn down the volume.

"The purpose of the treble bleed cap is to compensate for loss of treble due to the capacitance of the cable. The treble that is shunted to ground via the cable is compensated for by extra treble fed through the cap. The idea is to keep the treble and the lower frequencies roughly in proportion as you reduce volume. It’s a compromise, and with a single cap it only really is in balance for one volume setting, for a particular cable length. Turning the volume lower than this, there is too much treble bled through, and the sound is too bright.

Putting an extra resistor in parallel with the treble bleed cap seems to keep the tones in better proportion through a wider range of volumes. Although it is not perfect, it is much better than no treble bleed provision. My current view, best guess, is that for a 500k volume pot, a 1nF cap in parallel with a 220k resistor is a good compromise. It’s a matter of opinion however."





g) lowering the height of the switches so as to stop scratches your palms

That was easy, just put some washers under them.







Now let's just pray it will give work :-)
No strings yet, too late now, but there will be more to come,
especially on the bridge mechanics etc. So make sure to get your sledge hammer out for some metal work...


Looks just the same as before..