Tuesday, September 11, 2012

1975 Stratocaster Upgrades - Cruel Summer

Hot summer streets And the pavements are burning, I sit around

It has been another hot summer in my part of North Carolina, and I had to put things aside until the fall weather made it here.  A long to-do list added to the delay of work at the This Old Guitar workbench.  To help fill the gap, I've enlisted my old high-school pal / fellow guitar enthusiast /fellow engineer bj to be a guest blogger.  I hope you enjoy this posting that originally appeared on the Fender Forums:
This posting will chronicle the steps to swap my bridge pickup and a few other parts. I’m working with a mostly-stock 1975 Strat. Aside from being on the rotating pickup plan, I’ve rewired the selector switch to have the second tone control work the bridge and middle pickups. None of the changes I’m doing are innovative or otherwise special…I’m just gathering together a lot of information I’ve learned from this forum and other sources in one place, and hopefully clearly documented in case anyone is inspired to try it for themselves.

Our subject:

I’m replacing the current Seymour Duncan SSL-3, which replaced a DiMarzio SDS-1, which replaced the original. I’ve determined a SD SSL-6T is my pickup of choice. It is a good option for a basic vintage-ish sound to work with the originals, and a bit more punch when needed at the flip of a switch. The tapped/full output will be selected using a push/push switch on the bottom of a new tone pot.

For reference, I measured the DC resistance of the two original pickups and the two outputs of the new one, and the others I have:

Stock Neck: 5.82K
Stock Middle: 5.90K
SSL-6T Tapped: 6.75K
SSL-6T Full: 13.16K
SSL-3: 16.17K
SDS-1: 9.55K

So, going by resistance alone (Danger!)…the tapped output is a good fit with the originals. Also, the full output should have some kick to it, but nothing like the SSL-3. Aside from the curiosity factor, it is a good way to make sure there aren’t any wiring problems with the pickup before it is installed.

By the way, the SSL-6T is not an easy pickup to buy. Not impossible, just not stocked by any of the handful of places I checked. A special shout-out is made to Drew Bowman at Pro Audio Land for not only ordering it without any extra fee or hassle…but also for expediting the delivery to me when things got mis-routed arriving to him. So…if you shop online…consider PAL, just ‘cause they were nice to me :)

Here’s our new pickup:

In the process, I am also replacing the (well-worn) original 3-way switch with a new CRL 5-way. It is no longer possible to find and hold the ‘2’ & ‘4’ positions with any dependency, and certainly not in the middle of a song. Here, I narrowly succumbed to a bit of scope creep. During a moment of weakness, I thought of switching around which tone controls worked which pickups and and adding a second tone cap. Fortunately, I recovered and I’m sticking with the original plan of just changing the pickup…and replacing the tone cap with an Orange Drop of the same value…I can always mess with the wiring and other cap values later.

New Switches:

When it is all done, the completed wiring should look like this drawing:

Enough planning…let’s get started…

It is easier to remove the knobs while the pickguard is still attached to the body. Use two heavy picks, a slotted piece of leather, or two credit cards; but nothing metal. Work carefully and slowly until it comes loose. After removing the strings, move to the underside of the pickguard to start the disassembly. I like to keep a small bowl nearby to collect screws and other small parts. Put a towel between the pickguard and the body to avoid scratching the finish.

Before starting any disassembly, be sure you know where things are, and where they need to go…make notes, use little pieces of tape, take pictures…
Carefully unsolder the bridge pickup wires and pull them out of the way.
Carefully unsolder the wire connecting the second tone control to the cap on the first – it is usually the capacitor lead, so it might be easier to clip it…depending on your tools and skills. Unsolder the cap. Then remove the wires from the selector switch.

Carefully turn the pickguard over again and remove the tone pot, selector switch, and existing bridge pickup. Place them in a box for safe keeping.

Now...it looks like this:

Install the new pickup, switch, and pot, note location/orientation of lugs, etc. Adjust nuts on pot to set knob height to be even with the others.

So far, it looks like this:

Cut pickup wires to size, and twist/dress as needed to make it all fit well and look nice…unless you have a ‘swimming pool’ route, there isn’t a lot of space.

Solder the SSL-6T tapped- and full-output wires to the top and bottom lugs of one side of the switch. Cut and attach a wire from the center lug and add to ground bundle. Note: Duncan pickups are wound backwards from Fenders. The ‘ground’ wire goes to the selector switch. Confirm tap orientation with ohmmeter if unclear.

For this switch model, the lug at the bottom of the stack is connected to common when the switch is depressed. I’ll wire the tapped output to the lower lug, so the knob will be a bit higher when the pickup is in the full (higher) output mode.

Reconnect wires to selector switch according to the diagram.

Attach the new 0.047uF cap to first tone control in the same location and connections as the original. It is a good idea to use a small piece of heatshrink tubing on the cap lead going to the lug to keep it from shorting to the grounded can. As before, use the lead to make the connection to the second tone control. Attach a wire from the ground bundle to the body of the pot, not the housing of the switch.

And the wiring is done:

Clean up any solder spatters, flux residue, check wire routing to prevent pinching, etc.
This is also a good opportunity to lightly squirt some contact cleaner into any switches or pots that aren’t being changed…

Time to button it all up again and see how it sounds…

Aside from the functional changes, I’m taking the opportunity to address a cosmetic issue. With the original bridge pickup gone for good, I got a black cover for the current bridge pickup, thinking a completely different color was better than a slight difference between “new white” and “older white”. Now, I’d like them all to be the same shade as each other and anything but "new white". I did some reading and find reports of varying success with the “coffee soak” method, and decided to give it a try.

I purchased a set of white pickup covers and figured it would be too difficult to attempt a match to the existing ones, so I’m replacing them all with what should be an age-appropriate shade of faded white. I lightly buffed the covers with fine steel wool to break the surface skin to allow the coffee to penetrate better…and perhaps not completely evenly. I let all three soak for a while and check until they get to where I think they look good against the aged pickguard.

Here they are soaking nicely:

For those of you keeping a database, I used Trader Joe’s Dark French Roast (black, no sugar). The parts sat in the cold coffee for two hours, and came out looking like this:

One New, Two Old, Three Coffee-Stained

If I get inspired, I may attempt to stain a new set of control knobs as for some reason, the volume knob is a lot darker than the tone knobs. Perhaps it’s just worn more from being used much more than the tone knobs? Some other time…

Meanwhile, completing the assembly…

Lay the pickguard in place, being careful not to pinch any wires. To quickly check for problems, install one just string, more or less in tune, to make sure the pickups are all working and the various wiring and controls do what is expected – That nugget comes courtesy of the man from the angry red planet :mrgreen:

All is well so, attach pickguard with screws, add knobs and the remaining strings and tune it up.

Here is a comparison between the ‘down’ and ‘up’ positions for the push-push switch:

I’ve spent enough time adjusting pickup heights to know how thick a nickel is, so I set the new pickup more or less where it should be…and await the real test of the project…

The tapped output is a fine match for the stock pickups…clear tones with that bit of sparkle I was missing. The full output is certainly louder, but not nearly as hot as the SSL-3 (or SDS-1) and without the loss of high-end. It’s just enough to make a statement, without changing the tone too much…but not a substitute for an overdrive FX or a quick twirl of the Gain knob.

What I didn’t expect was how much the tone control would change with the new cap. Over the years, I’ve read the discussions over values…usually 0.022 vs. 0.047, and what roll-off is better for what kinds of sounds. The comments (and the physics) support high capacitance values giving lower resonance peaks and otherwise ‘dark’ tone settings (higher corner frequencies), but my stock cap (0.05) didn’t seem overly dark last week as I worked the controls to form a reference in my mind as a comparison…but I was curious…and as mentioned earlier, I was tempted to throw in a 0.022 just to see the difference.

Now, I realize what dark really meant. Apparently, and very slowly over time, ceramic capacitors (usually Barium Titanate or similar material) lose capacitance as the crystalline structure relaxes. After 35 years, there seems to have been quite a shift which was totally unnoticed to me (think about the slowly boiling frog), but after installing the fresh capacitor the tone gets very, very dark when the control gets below about 4. I’m not ready to swap it for the 0.022 yet, it’s actually very cool in a jazzy, bluesy kind of way…but I mention this as an advisory for those with old guitars…and old tone caps…that the tones you hear now may no longer be what they were when first manufactured.

I’m very happy with the project. It looks better with matching trim and I’ve got a variety of new sounds to explore…enough typing…I’ve got some playing to do…

1975 Fender Stratocaster
2012 Taylor GA3-12
1967 Epiphone Madrid EC-30

"Make every song you sing your favorite tune."

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