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Squier Vintage Modified Jazzmaster Modifications, Pt 4: Wiring Mods

I probably should have put this picture in at the end of the last post.  However, I did not.  Oh well.

The other part of shielding your electric guitar is the body cavity.  I used copper shielding for this part - it's easier to handle than aluminum foil.  Plus I had purchased a sheet of 3M foil and wanted to try it.  It worked great - I just made some templates of the various curved areas and then used them to cut the appropriate shape from the sheet.

When the pickguard is on the guitar, its shield will touch the copper body shield and form a shield around all of the electronics.

I wanted to have some different tonal options on the guitar.  The most straightforward was putting a Fender TBX (Treble-Bass Expander) control in place of the stock lead circuit tone control.  The TBX is a unique stacked pot with 2 different values and some trick changes to the pot tracks.  It has a detent in the center, at which point the control is like a standard tone control at "10."

Turning the control one way rolls off treble like a standard tone control.  But turning it the other gives a bass cut.  Pretty neat.

One mod I did based on some research on the interwebs is changing the wiring a bit from 'stock' and using a 220K resistor in place of the 82K that comes with it.  This allegedly gives a smoother transition from one mode to the other.  The picture above shows how I wired it.  The cap is an .022 uF.

If you read the last post, you'll note in this post I'm giving up on the silly "mod" numbers.  I'll list them at the end, when I get there.

I also am changing the rhythm circuit.  A lot of players find it too dark and don't use it.  I know I wasn't going to use it much.  If I want dark, I'll just roll off treble.

In looking at the schematic, I noticed that Fender did something on the rhythm circuit which is probably unique compared to any other electric guitar (and is shared by the Jaguar).  The hot lead of the neck pickup goes to the tone pot first, then on to the volume pot.  The tone pot is also only 50K, so both the wiring and the value of the pot really set the tone (ha ha) for it being dark and mellow, and having less volume as well.

I did consider leaving the wiring off entirely, but then I got an idea.  After putting the TBX control on the lead circuit, it occured to me that I could wire up a bass cut on the rhythm circuit!  The tone I'm aiming for is that clean, jangly 60's rhythm tone.  Totally the opposite of a stock Jazzmaster.

To that end, I put a 250K linear pot in place of the 50K stock tone pot.  I also found out the stock Alpha pots on these Squier don't line up squarely on the bracket - there is a mounting hole that fouls them.  So I sanded off a bit of the phenolic part of the pot to get a better fit (see the picture).

Then I used a simple high-pass filter network to replace the old tone control.  The hot side of the neck pickup now comes into the volume control as you'd expect.  And we have an .02 cap going to the input of the tone control, with the center lug grounded.

Depending on the position of the tone control, the frequency cutoff goes from about 62 Hz (pot on max resistance) to over 7 kHz at no resistance.  So for the first third or so of the rotation, we get a cutoff of the bass and lower midrange frequencies.  Turning it more will just roll off mids up through treble. 

I did some maths (as they say in Britain) to figure out the rolloff frequencies for the high-pass filter and came up with these values to use.  The proof will be in the actual use - it may need some finessing.  But testing on the bench I can confirm it seems to work as designed.  If it's useful, I'll be able to preset that tone and just hit the rhythm switch when I need it.

Here's the whole newly modified wiring harness mounted on the pickguard.  There are three main grounds - both of the pickups and the output ground - that come together.  I'll run those to a star ground on the body.

I covered the pickup hot leads with shielding just for the heck of it.  The shields are grounded to the foil.  There are also three local grounds that were unavoidable - the rhythm circuit, the volume pot, and the lead pickup switch.  I could have run them to the star grounds, but it didn't seem worth it.

The wiring is much cleaner than the stock Squier wiring.  I could probably market this as an assembly!  Hmmmm.

Next I'm replacing the stock bridge thimbles with Mastery stainless steel thimbles.   I'm going to put one of their bridges on too, so I figured I'd do the thimbles as well, since they will have a much better fit to the bridge.

The Mastery thimble is the one on the right.  Really nicely made.  It's also a tad bigger than the stock Squier thimble - I just reamed out the holes in the body some.

I wanted to solder the "bridge" ground to a thimble, but since they're stainless, I needed silver solder.  I have some somewhere in the Dungeon, but darned if I could find it.  So I just stripped about an inch off the ground lead, tinned it and stuck it in the hole so it would contact the thimble.

The thimbles are going to be a nice tight fit.

I reamed the holes so they'd press in partway, and the I could use my rubber mallet to whack them down... so!

I love that mallet.  Best $12 I ever spent.

Here's the grounds going to the new star ground.  I reused the two leads with lugs from the original wiring.  You can see the ground on the right which passes up to the thimble.

 One more quick thing.

When I bought the guitar, it didn't come with a vibrato arm!  (I bought it as a 'refurb' on ebay).  So I needed a new arm.  Have you ever tried to figure out specs for a MIA Jazzmaster arm threads?  All sorts of contradictory info out on the interwebs.

So, I just cut to the chase and bought a nice new Fender Jazzmaster US reissue vibrato assembly with arm rather than try to get a Squier arm.

I'm actually tickled with it.  It's on the right in this picture - the Squier version is on the left.  I has the vintage-style lock button on it, it's made of much better material, the spring seems heavier, and it's even signed!

And it bolts right on perfectly.

All Posts on the Squier Vintage Modified Jazzmaster Modification Project:

Part One: Starting Disassembly
Part Two: Removing Factory Wiring
Part Three: Shielding
Part Four: Wiring Modifications and Curtis Novak Pickups (This page)
Part Five: Neck Inserts and Installing Mastery Bridge
Part Six: Buffalo Bone Nut and Final Setup
Part Seven: Modified VM Jazzmaster Visits the Garden
"Ching" Rhythm Circuit Revisited: 28 April 2014 


Post a Comment 6 comments:

  • BillB64 said...
    November 9, 2013 at 11:34 AM
    Hey bud, where did you get the US trem plate from? Thanks, Bill.
  • Yr Fthfl Blggr said...
    November 9, 2013 at 11:57 AM
    Hi Bill -

    I got it from Angela Instruments:

  • nug nug said...
    January 20, 2016 at 12:05 AM
    this is probably a late comment but how did the star ground work out for you?
  • Yr Fthfl Blggr said...
    January 20, 2016 at 9:11 PM
    Never too late to ask a question! Thanks for asking.

    The star ground works well. The original wiring was a real mess, which I mentioned in my posts. It depended on a lot of local grounds via pots or switches. A lot of potential for ground loops abound.

    I use that type of grounding on amps I build as well as guitars. It's just good wiring practice, and more reliable. Easy to do as well.

    Plus, the black paint which people seem to think is shielding paint, is most definitely not...I tested it for continuity and it has none!

    So cleaning up the wiring (and taking a couple feet of excess wire out...) and using a star-grounding scheme and shielding it made it quieter.
  • Håvard said...
    February 15, 2016 at 6:27 PM
    My modding skills are very limited, so if I just want to fix the grounding issue, what is the easiest way to do it on the stock guitar? What spaghetti end to connect where?
  • Yr Fthfl Blggr said...
    February 17, 2016 at 4:01 PM
    You need to identify all of the grounds and run them to a common ground point. If hum is a concern, you should also shield the cavity as I did.

    This is a great site with tons of information explaining the process. It may help to read this:

    Do you know someone who could help? A JM isn't the easiest guitar to start on. Do you have a simpler guitar to try first? Like a Tele?

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