Thursday, August 7, 2014

Mellow Yellow Bass Kit Build

What?  Another bass kit?  Had I lost my mind?

I hadn't planned on building another bass kit, honest.  (See my experiences with my previous kit here:  But while searching ebay last year, I came upon this kit:

A classic body look similar to a '51 bass (which I've always been partial to).  And, most importantly, there was a lefty version, too!

And it had a humbucker?

OK, I was intrigued.  I'd never tried a lefty humbucker bass; this might be my chance.  But what was with the weird (and amazingly ugly) headstock shape?  Looked like the headstock was trying to morph into a pumpjack.

Well, I figured I could probably fix that with a saw.  So, what the heck.  I ordered one.

It's here!

The box arrived...

OK, first things first, I took inventory.  Everything was there this time.  But the control plate was made of plastic (the same material as the pickguard -- guess they didn't have a lefty version in metal).  And again, the nut was a righty version (the built-in slope is in the wrong direction).

But none of these were show stoppers.  So on to the next step:  completely assemble and check that it sounded halfway decent before investing time and money to reshape the headstock and paint the body.

First, mounting holes needed to be drilled for the following:
  • Pickguard
  • Control Plate
  • Jack plate
  • Pickups
  • Bridge
  • Strap Buttons
  • Tuner Screws
  • String Retainer
I also drilled out the 4 holes in the body for the neck screws -- they were too small, and the neck screws would have bit into the body wood as they were being screwed in, which was something I didn't want.  The screws should pass through the body unimpeded and only bite into the neck wood.  Otherwise, I would run the risk of not being able to adequately tighten the neck to the body.

As I assembled the bass, I discovered a few more issues.  Some of my own making, some not.

First, my mistakes:

1.  I initially mounted the bridge a little to close to the neck pocket, so that when I tried to setup the bass, I discovered that the saddles were getting very close to the back of the bridge.  Redrilled five holes closer to the end of the bass and filled the first five holes with bondo (next time will use dowels):

2.  Made the holes for the tuner screws slightly too small (I think).  One of the screws broke when I was screwing it in to the headstock: 
Had to dig a bit into the wood so that I could grab the broken-off end with a pair of pliers and unscrew it.

And the manufacturer's issues:

1.  Right-handed nut, not a lefty (slots sloped the wrong way).  I first tried filing the slots to give them the proper slope (towards the headstock, not the bridge), but this put the strings so low that they would rattle on the frets between the nut and the fret I was fretting when I plucked a string.  So I found another nut in my spares box and installed it.  (In hindsight, I probably could have just added a shim below the original nut after I'd filed it.)

2.  The pickup route was just a bit too small for the pickup's mounting ears!  Fixed with files/sandpaper applied to sides of the pickup cavity.

3.  Neck cross-section not symmetric.  Looks more like an airplane wing.  Can't fix it, but it doesn't seem to be a problem.  Just sloppy manufacturing and poor quality control.

 4.  One end of the third fret is a bit short:
Not going to fix that,

5.  Sharp fret ends:  file them down.

6.  Neck plate not squared to body (i.e. body holes and pocket not squared to body):  File the body holes for the neck bolts so that they're a bit wider, to give some room to square up the neck and sand the sides of the neck pocket to give me enough range of movement.

7.  E-string tuner slightly offset so that when only the E-string is installed, it wants to slide the nut sideways.  Not a big deal, but still...

On the plus side, the frets seem level this time.

Assembly is done, how does it sound?

Plug it in and turn on the amp.  Wow!  Lot's of hum!!!

Wiring looks OK -- let's see if shielding helps.

First, let's pick the low-hanging fruit and shield the control cavity and the plastic control plate with 1/2" copper tape from the junkbox:

Hmmm...still lots of hum.  Must be capacitive-coupling to the pickups.  Let's shield the heck out of them:

First, wrap each of the coils in copper tape:

Then add tape to the top of the pickup:

Note that these top pieces of copper tape are soldered to the copper tape on the sides of the coils, so that there isn't any solder on top of the pickup that might prevent the pickup cover from going all the way onto the pickup body.

 And finally, add copper tape to the back of the pickup:

This may be going a bit overboard, but I figured better to do as much shielding as I could, all at once, rather than piecemeal.

All pieces of copper are connected together with solder (spot-tacking is fine), and then attached to the pickup ground at one spot.

Reinstall the pickup and test:  no more hum!!!
[Sidebar on hum:  I believe that humbuckers get their name from preventing magnetic-field induced hum.  Unfortunately, the hum I usually experience is not from magnetic fields, but from electric field interference that's capacitively-coupling to the pickup windings, and unless the pickup has appropriate E-field shielding, magnetic-field counter-measures (e.g. bucking coil windings) will have no effect.

Fortunately, E-field shielding is pretty straight-forward.  What you want to do is provide enough shielding (i.e. conductive surface tied to ground) near the pickup so that the majority of the electric field interference is shunted (via capacitive coupling) to this surface, rather than to the coil(s) of the pickup.

For further reading, check out the capacitive-coupling section in Chapter 2 (Cabling) of the book, "Noise Reduction Techniques in Electronic Systems, Second Edition", by Henry W. Ott.  Great book!]

This amount of shielding will have some effect on the sonic properties of the pickup -- essentially, it appears as extra capacitance from the pickup to ground.

In this case, my shielding added about 0.5 nF to the output of the pickup.  Given that the tone-control's capacitor is 47nF, and that I usually play with the tone control near 0 ohms (i.e. fully, or nearly so, ON), this additional amount ( 1 % ) would seem to be insignificant.

An Aside on the Pickup's Placement

OK -- the bass sounded pretty good!  And I was wondering how the pickup was placed relative to the 12th fret.

The centers of the neck-side poles measured roughly 13 inches from the hump-top of the 12th fret.  That's very interesting, because, according to internet sources, the same poles on a Musicman SR4's pickup are about 13.125 inches from the 12th fret.

In other words, the placement of this humbucker is within 1/8 inch of an SR4's humbucker.  Maybe this accounts for its sound?

I was also quite surprised, because from the pictures, I thought that the pickup was higher up, placed in a position close to where a P-bass's pickup would be.  And then I looked more closely...

Hmmm -- although the pickup is placed next to the pickguard, the bridge is actually fairly far away from the rear end of the guitar.

And the neck has 22 frets, not 20, and the neck pocket isn't as "long" as a typical Fender pocket.  That is, the neck juts further out of the pocket.  (This also means that I cannot replace this neck with a neck drilled with the standard Fender hole pattern -- it won't sit far enough into the neck for its holes to line up with the body holes).

The overall net effect of these changes is that the neck and bridge have been shifted in position towards the neck-end of the body, which is the same as if they'd not been changed, but the pickup had been moved instead from the standard P-bass position to one closer to the bridge, similar to a Musicman pickup position.  But now the bass is roughly 1 3/4 inches longer than my P-bass.

I'm happy with the sound, let's continue on...

Working on the neck and headstock.

First, let's take care of that ugly headstock.

Not a lot of wood to work with, but what the heck.  Tackle first with a saw, then a sanding bit on my drill, then file and sandpaper.  Here's the result:

Much better!

Here's the bass in its fully assembled yet unpainted state:

I then removed the neck and its hardware, and then finished the neck with brushed-on Minwax Fast-Drying Polyurethane (clear satin) and hung to dry.  Once dry, I sanded down with 1000 grit sandpaper.

Painting the body

Now to paint, sand, and then polish the body.

Again, just like my previous project, I'm following (pretty much) the steps in the book, "How to Create a Factory Guitar Finish with Just a Couple of Spray Cans!", by John Gleneicki.

1.  Strip the body of all parts. 

2.  Sand the body and then fill any small dings and divots that I found with auto-body bondo.

3.  Spray the body with a can of Spraymax 2K Glamour High Gloss Clear Coat to act as a body sealer and filler.  Here's the body after this step:
The red spots on the body are bondo patches.  (The wood is so soft that it dents if you look at it sideways.)

4.  Sand the front and back of the body flat with a wood block and 320 grit (dry, not wet).

5.  Because the body wasn't too flat to begin with, this last step resulted in me sanding back to wood in a few spots.  So I sprayed another can of the Spraymax 2K and repeated the leveling of front and back with block-sanding using 320 grit (dry).

6.  Wait 3 days, then spray with primer.  When dry, lightly sand with 600 grit (dry).

7.  Spray the color (base) coat. 

Here's the primed body, waiting for base coat, in my homemade painting jig (jig described here:

8.  Wait 2 days, spray with a can of Spraymax 2K Glamour High Gloss Clear Coat over the color coat.  Note: you don't need to sand the color coat if using urethane color coat.

9.  Wait another day, then sand with 600 grit (dry) and spray another can of Spraymax 2K Glamour High Gloss Glear Coat.

10.  Wait a week.

Before we continue on, let me add a few more pictures.

Here's a shot of the types of paint I used.  Middle can is the base color:  VW "Mellow Yellow", custom mixed at "Jerry's Paint and Supply" in Sacramento.  PPG code 902738.

The Spraymax can has a slightly different label from the cans I used last year: now there's "368-0061".  No idea what that means.  New formulation for California?

My painting worksheet.  Click on it to enlarge.

A tip!  If using a trigger-handle for your cans, tape it to the can.  I found that cans could rotate in the handle, and if I wasn't paying attention I'd end up painting the inside of the trigger-handle, rather than the body.

Sanding and polishing the finish

A week has passed.  Time to remove the neck stick and start sanding.

Body before sanding begins:

First, I'll note that all of the sanding is done with wet sandpaper.  I start by soaking the sandpaper in a bowl of water for a few minutes, then, while sanding, I'll frequently dip the paper back into the bowl to keep it moist and to clean it off.

This means that the body gets pretty wet!  It's important that this water not get into any holes, as the wood will swell and you can easily sand through your coats.  This time I plugged them with wax from a candle -- I let melted wax drip over each hole, and while it was still soft and malleable I pressed it into each hole.  I then gently scraped away the remaining wax (use fingernail or soft tool).

This worked very well -- no unintended swelling this time!

Regarding the actual sanding,  Gleneicki goes into a good amount of detail in his book, so I'll just summarize what I did:

1.  Sand top and bottom (but not the tummy and arm contours) with 320 grit, wet, using a wood block.

2.  Sand top and bottom and tummy/arm contours with 400 grit, wet.  No block (paper held in fingers).

3.  Sand the above, plus sides (but not edges), with 600 grit, wet, no block.

4.  Sand the above, plus gently-rounded edges, with 800 grit, wet, no block.

5.  Sand the above, plus sharply-rounded edges, with 1000 grit, wet, no block.

6.  Sand all of the body with 1500 grit, wet, no block.

7.  Sand all of the body with 2000 grit, wet, no block.

Ooops, a boo boo!

While sanding the sides, all of a sudden I saw white primer (probably because I actually used 400 grit on the sides and also didn't adequately spray on the second day's clear coat.  Next time, 600 grit!).

Heart stop!
(Click on image to enlarge)

Can I fix it?

Fortunately I had a bit of paint left in the can (tip:  don't spray it all out when painting the body.  Leave a little in the can, just in case).

So I masked off the body, revealing only the primer and a bit more of the body around it...
...and sprayed it with color: 2 tack coats, 3 (or was that 4?) wet coats.

After the paint had dried, I sanded down its edges and then added an enlarged mask for a new layer of clear coat (fortunately, I had purchased an extra can of Spraymax 2K.  So the cost to fix the boo-boo:  $20!).

(Clear coat:  2 tack coats, 4 wet coats).

Here's the body, waiting for the clear to cure.

After a few days I removed the mask.  If you look closely, you can see the edges of the new clear coat.
(Click on image to enlarge)

I then sanded the new clear coat patch, removing its "orange-peel" and blending its edges, first with 1000 grit, then 1500, then 2000, all wet.  Here's how it ended up:

Looks pretty good to me!

Polishing the finish:

After the final sanding with 2000 grit, I polished with Turtle Wax "Polishing Compound" that I'd picked up at a hardware store.  Rubbed and sweated, rubbed and sweated, rubbed and sweated (hey, it's summer, and it's been hot and humid recently!)

Finally got it to a point that I was satisfied with it.  The surface isn't as flat as I'd like it to be (i.e. perfectly flat), but it has a nice mirror-like sheen.

Here's the end result:

Not too bad!

Final Thoughts:

1.  The new Spraymax 2K seems to take a bit longer to cure (but I could be wrong).  I have some very small dings in the body where some hard objects pressed into the body (such as my car keys in my pants pocket) while I was holding the body against me and aggressively polishing its sides.  Not a big deal, but maybe try 2 week cure before starting sanding?

2.  In the same vein, pot life in the can seems to be longer than 24 hours.  With the can I used to fix my mistake, I noticed that it seemed good at least 48 hours afterwards (and perhaps 72?).  Again, perhaps it's a new formulation?

3.  Next time, I might try sanding with higher grits before I begin polishing.  Perhaps 2500 or 3000.

4.  Don't use bondo to fill holes -- it shrinks as it drys, and thus can sink.  Use bondo for shallow dents and dings.  Fill holes instead with wood dowels.

And the standard caveat:

This is a learning process for me.  Never assume that what I've done is the best way to do it, or even the correct way.  Use your own judgement and common sense.  Or ask an expert.

And if you know of a better way to do something, please let me know.  I'm always interested in learning new tips and techniques!

And one more thing...if you're thinking of buying a kit to save money, don't do it!  You can get a decent guitar, used, for less money than you'll spend on the kit plus paint plus tools.

Links to Bass posts of mine...

Sonic Blue Bass (part 1 of a 3 part series)

Mellow Yellow Bass

Short-scale Telecaster Bass

Bass Guitar Painting Jig

Repairing a G&L Butterscotch Blonde Paint Chip

G&L ASAT Bass Strap-button Extender