Oddball '84 Fender Esprit pickups (measures and questions)

[nuke]

I have a 1984 Fender Esprit Elite, really great, rare guitar, made in Japan under contract to Fender in the early 1980's. This was eventually re-branded to the Robben Ford model. The instrument is a chambered alder body, smooth heel, maple set-neck, Schaller hardware and pickups.

The "master series" were the Elite and Flame semi-hollow, and the D'Aquisto hollow "jazz box". All designed and overseen by D'Aquisto.

All of them feature an oddball set of Schaller humbucker pickups, with a full black plastic cover with exposed slug and screws, 3-screw mounting system (x and y tilt), 4-wire split coils.

My Elite model is equipped with a coil split switch and Fender TBX tone controls and 1-Meg pots. (all MIJ Alpha pots). This was one of the earliest TBX-equipped Fenders.

So - why am I messing with it? I find the humbuckers curiously dark sounding.

The Robben Ford model was eventually re-equipped with Seymour Duncan 59 neck and JB-bridge and the TBX replaced with standard tone circuits. I have one of those guitars and I find it too bright, and I'm not a big fan of the SD 59, they're ok, but can be a little strident.

I like the original Esprit a lot, it really gets into the ES335 territory, but lighter, and comfortable size, and versatile with the pickup splitting. 

Next post will have some data. 

[nuke]

Ok, now for some data:
DE5000 LCR and WT10A Teslameter

Neck (both coils - humbucker):

Pole spacing (Schaller neck, slightly narrower than bridge)
Magnetic polarity:  Screws south (normal)
Magnetic strength: 45mt  (450 Gauss), peak measure at pole piece. 

LCR meter data (both coils, wires disconnected)
LS 5.24H at 100hz, Q 0.416
CP 64nf
CS 434nf
RP 10.34k
RS 8.815k
DCR 8.757

Neck (split coil)
LS 2.597H at 100hz, Q 0.371
CP 118.32nf
CS 975nf
RP 4.999k
RS 4.394k
DCR 4.355k

Bridge (both coils - humbucker)

Pole spacing (Schaller bridge, slightly wider than neck)
Magnetic polarity: Screws North (reverse polarity)
Magnetic strength 45mt (450 gauss, peak at pole piece)

LCR meter data (both coils, wires disconnected)
LS 9.1H at 100hz, Q 0.415
CP 40nf
CS 278.2nf
RP 16.148k
RS 13.773k
DCR 13.645k

Bridge (split coil)
LS 4.120H at 100hz, Q 0.376
CP 76.34nf
CS 616.3nf
RP 7.839k
RS 6.869k
DCR 6.805k

[stratotarts]

What are the questions you mentioned?

[nuke]

Notable is the use of reverse magnetic polarity on the bridge pickup. They also use different windings for the split coil function. It is a single mode switch on the guitar, both in humbucker or both in single-coil. The reverse polarity and opposite coil wiring allows a RWRP hum cancel in single-coil mode with both pickups selected. In HB mode, the phasing is the same, due to the opposite wiring used. 

The wiring is sort of odd, 1M volume pots along with the Fender TBX tone controls. The 82k resistor is in circuit at the "5" detent and lower on the TBX, but is effectively off at higher settings. (see the discussions of TBX elsewhere, I posted photos of this particular version there some time ago). I've tried disconnecting the tone controls entirely, expecting a very bright tone with the 1M volume pots, but it seems the pickups are just pretty dark on their own. 

Feeling adventurous, I removed the bridge pickup and took off the cover to view the internals.  While it is oddball from the outside, and features a unique 3-point mounting system, other than the full plastic cover and the specific base plate, it seems more or less to be just like any other Schaller humbucker from the 1980's-1990's.  The base plate is silver in color, with a white plastic overlay, then the standard bar magnet, keeper-plate for the screws, plastic spacer under each bobbin.  I couldn't tell what the magnet was, due to being short and hidden under the boobins and the amount of glue and wax (potted) present. It is dark in color, but also appears that the upper surface is rough, perhaps sand cast. It might be ferrite, but suspect it is alnico.

[stratotarts]

The magnet must be Alnico. Can you be more specific, "reverse polarity on the bridge pickup"? What do you mean? BTW some Ibanez also have the RWRP split coil configuration using HB in one switch position, IIRC.

[nuke]

So where am I going with all of this?

I like the instrument, and would like a little more openness and sparkle from the pickups. It is possible to jam a set of off-the-shelf humbuckers in there, but given the pickup routes being specific, they just don't look that great. I'd like to keep the original look and mounting scheme. 

Schaller quit making pickups some few years ago. But it seems possible that the bobbins and internals from another Schaller HB can be transplanted onto these baseplates and fit the covers pretty easily.  

Or, these could be modified with different magnets, or re-wound. 

Hence, the data collection and need to understand where I'm at with these, and what parameters to target to get what I am looking for. The underlying guitar sound seems to be there, just a bit veiled by the pickups. They're quite usable, but hey, who's happy with status quo? LOL

[nuke]

By reverse polarity, I mean the magnet polarity is reversed from the neck pickup. Most "PAF" style humbuckers follow the "screws south, slugs north" magnetization. The Neck pickup in this pair is that way. 

The bridge pickup in this pair has the opposite magnetic polarity, meaning the screws are *north* and the slugs are *south*, which is reverse from the normal convention. 

The neck and bridge are wired in the guitar for opposite coils. You can see the slugs are the yellow/white wires and the screws are brown/green wires.   

In the guitar, the neck volume is the brown wire, the bridge volume is the yellow wire.  This effectively reverses the winding directions between the two pickups. This would give RWRP in single-coil mode operation of both pickups, and in-phase signal when in humbucker mode. Clever wiring scheme really. 

See attached for the wiring:

[antigua]

Thanks for the details. The inductance values are very high for the bridge pickup, and rather high for the neck. 9 henries is hotter than a JB. I'm not surprised Robben Ford chucked all of it out. 

The only way to add sparkle back once you have pickups with high inductance, aside from split or parallel, would be to install a Bill Lawrence Q Filter, which is an inductor with a cap and resistor added in, which effectively lowers the inductance of the pickups. If you can't dedicate an tone control to a Q Filter, you can wire it as a push pull, so that it's other in circuit or out of circuit. 

The single button split with B+N single coil humbucking is similar to how they set up the new Meteora model with the Fireball humbuckers. 

[ecmalmo]

If the bobbins are the same dimensions as regular humbucker bobbins I would just wind a new set of bobbins and install in the original baseplate. But keep the original bobbins if you ever want to restore it. 

Around 5000 winds of 42 AWG per coil if you want the PAF thing, 6000 winds of 43 if you want something more modern but still not 9H hot.

[nuke]

Well, I should say, it doesn't sound "bad". Robben Ford got a lot of mileage from the Fender Esprit and got famous playing one just like it back in the day, before they re-named it the Robben Ford signature model.

Compared to my USA masterbuilt Robben Ford, with the spruce top, Duncan 59/JB pickups, 500k pots and treble bleed on the volume. It's gorgeous, but quite bright in comparison. I got it secondhand in Japan some time ago. Ford is a big guitar hero there.

I have a '98 Heritage H150, which came from factory with Duncan 59's. Heritage for some reason back then, equipped it with Norlin-era pot values: 300k volume and 100k tone pots. That sucked all the brightness out of them. With normal 500k pots in it, the SD59's are a bit bright and a little ice-picky.

The Esprit is not quite as dark as my Heritage H150 was with the 300k vol and 100k tone pots. Go figure. Like I said, it isn't bad, just curiously on the dark side of tone. Set the right EQ on the amp and all is good.

Just trying to figure out the basis for why, since it isn't the pots/tone setup, it is the pickups themselves.

Since it isn't as simple as minor wiring changes, and the unique form-factor precludes simple pickup swaps, decided to dig into the pickups more directly to understand what's going on and what, if anything, I might do with them.

[nuke]

Getting back to the pickups:

They are 1980's era Schaller pickups, much the same as the eleventy-bazillion Schaller humbuckers made in the 80's and 90's and put into all kinds of guitars, especially pointy ones back then.

What is unique on these is the baseplates and the covers, the rest would be the same as garden-variety Schaller HB's of the era. But that's different than Gibson, Dimarzio, SD, etc. So the bobbins, magnets, spacers and stuff aren't interchangeable with anything other than similar Schaller parts

What that means is "regular" parts don't fit exactly. Schaller had their own unique bobbins, magnets, baseplates and even slightly different pole spacing for neck and bridge pickups. Most of the "DIY" pickup parts follow the Gibson pattern, especially whatever is purported to be "authentic PAF" whether it is or isn't.


Any mods would entail harvesting suitable parts from other Schaller humbuckers. There are millions of such in junk drawers all over the place. People used to routinely yank them out for whatever. And Schaller made them in all kinds of winds and flavors, from pretty decent vintage style PAF's, to hot uncovered ones, with slot-screws and slugs, allen head screws and slugs, double-slugs, double allen-head screws, custom colors, alnico and ceramic magnets and so on. Whatever the OEM wanted. Many of them were overwound, ceramics, intended for the pointy-guitar-dive-bomb-tremolo market that was hot back then. (I'm that old)

My quest is to understand these first before hacking anything. I don't want to screw up a good thing and these pickups are quite hard to find.

The technical measurements are first-order spot checks, so subject to whatever the LCR meter can do. Was reading through the articles on how to measure pickups, so ordered the LCR meter and Gaussmeter that seem to be commonly used. I'm an EE in real life, have a decent bench and a scope that can do Bode plots. Haven't set it up for pickup measurements yet, still reading the other articles on that.

[antigua]

The Bill Lawrence Q Filter is a non destructive mod. In theory you could wire it up outside of the guitar, between the input jack and the guitar cable, with a little box. The inductance values are so high that I'd consider the dark tone question and open and shut case, regardless of the 1 meg pot or anything else. 

When you measure value with the DE-5000, you only need:

Ls at 100Hz (the lowest freq)
Cp at 100kHz (the highest freq)
Q at 1kHz (a value that is both high, and still below resonance, to measure eddy currents) 
DCR (plain old DC resistance)

The other values are not needed, either because they're not very useful or they're not applicable.

The resistance at frequency measurements, Rp and Rs, might actually have some use in eddy current determination, but I havent looked into it yet. The thing about a PAF clone is that because they all use mostly the same parts and geometry, the eddy current aspects are usually known, from having observed them in so many other PAF clones. It's mostly useful when you have reason to believe a given pickup will have more or less eddy currents that you would expect, like if the pickup maker claims they're using nickel silver, but you suspect they've used brass, or something like that.