Tar Backs?

[PoorMan]

I got a Tar Back that a customer wants me to bring back to life for him. Interesting pickup.

The legs are missing...


Anyone have any info on them? I believe designed by Bill Lawrence, low resistance, ceramic mag. Were the baseplates brass or nickel silver? Can you get baseplates for them? Appears the baseplates were not grounded?

[David Schwab]

Did it have a base plate? Usually they just have a brass bar with the mounting tabs:

[David Schwab]

Here's a set of covered Dirtyfingers I used to have. Same construction:

[EFK]

Are you sure those are Dirty Fingers? I always thought all Dirty Fingers had dual screw bobbins. They look like potted Velvet Brick pickups, which is also what I believe constituted most "tar backs." The Velvet Bricks were stock T Tops, low resistance, with a double thick ceramic mag and two leads from the baseplate for coil tapping. Some were uncovered stock for use in Firebrands, Sonex guitars and the like. The tarbacks I've had out of mid 70s guitars seemed to be the same as t tops with stronger mag pull, so I figured when Gibson started using them uncovered and unpotted in later 70s guitars, they just renamed them Velvet Bricks for marketing purposes. They used that horrid black epoxy in the black minis, too, that they stuck in some SG specials etc. I'll bet some purchasing genius at Gibson accidentally ordered a bunch of vats of that crap ("Dammit Bob, we said black lacquer!") so they figured they needed to do something with it! hahahahahaha

[David King]

I'd just hot-glue on an omega shaped bracket with tapped holes to replace the busted tabs. You'll need a 3-48 tap, a 5/64" or 2 mm drill and a strip of K&S .031 x 1/2" brass (all hobby shops).

[David Schwab]

Are you sure those are Dirty Fingers? I always thought all Dirty Fingers had dual screw bobbins. They look like potted Velvet Brick pickups, which is also what I believe constituted most "tar backs." The Velvet Bricks were stock T Tops, low resistance, with a double thick ceramic mag and two leads from the baseplate for coil tapping. Some were uncovered stock for use in Firebrands, Sonex guitars and the like. The tarbacks I've had out of mid 70s guitars seemed to be the same as t tops with stronger mag pull, so I figured when Gibson started using them uncovered and unpotted in later 70s guitars, they just renamed them Velvet Bricks for marketing purposes. They used that horrid black epoxy in the black minis, too, that they stuck in some SG specials etc. I'll bet some purchasing genius at Gibson accidentally ordered a bunch of vats of that crap ("Dammit Bob, we said black lacquer!") so they figured they needed to do something with it! hahahahahaha

I should have this saved somewhere as a text file, because I have typed it so many times. Yes, those are Dirty Fingers. And yes, they usually have open double screw coils. Here's the story; that set of pickup came off of a 1980 Gibson ES-347. The guitar belonged to Charles Smith of Kool and the Gang. It was given to a friend of mine who was one of their touring musicians at the time, and had never been played. Charles had a closest full of guitars that he never played! Several closets. He showed me a whole bunch of guitars one time. This one still had all the tags and everything on it. Gibson had just introduced the Dirty Fingers, and for this guitar, they used closed gold covers, because the guitar has gold hardware and all.

This is an ES-347:



So the question is always, how do I know they are Dirty Fingers and not one of the other Super Humbuckers?

That's simple.

First, the guitar still had all the tags on it, as well as a sticker on the pickguard, it they said they were Dirty Fingers. The little booklet that came with the guitar talked about the DFs too.

Second, they have the coil tap wire. That's the second switch on that guitar. The Super Humbuckers did not have the coil tap wire.

Lastly, they were 16k. Since Dirty Fingers were and are Gibson's hottest pickup, you can see that they aren't the Super Humbuckers, which only got up to about 14k.

The guitar was given to an old friend/customer of mine, who did not like the pickups at all. They are a bit too hot for this type of guitar. So he had me change them out for Duncan Alnico II Pros, and he gave me the pickups. I had one in my Charvel CX 290 for a while, but it was a little noisy when I was recording, so I removed it and sold them on eBay.

There's not a lot of difference between the Super Humbuckers and Dirty Fingers, except the Dirty Fingers were wound to 16k. So they are over wound Super Humbuckers, and then on the usual uncovered version they used two screw bobbins. They both use three ceramic magnets. On this one they just built them like the Super Humbuckers.

Here's Gibson's press release when they reissued the DFs:

Gibson reunites power and dirt in Dirty Fingers guitar pickup

The original Dirty Fingers pickups were available on just a few select models in the early 1980s, including the Flying V, Explorer, ES-347 and 335-S.

[Stratz]

Did Gibson make any other model humbuckers in the early to mid 80's with triple ceramics around 16k ohms?

[David Schwab]

Did Gibson make any other model humbuckers in the early to mid 80's with triple ceramics around 16k ohms?

None were 16k except the Dirty Fingers. But they had the Super Humbuckers, which was a name they used for a bunch of different pickups such as the Series VII, but they are 6.5-7.5 Kohms. The hottest of those I have seen was about 13-14k.

Getting back to whether or not those are Dirty Fingers, someone posted a PDF of one being dissected. In that they wrote:

Introduction
There’s a bit of controversy as to what pickups were used in early Gibson ES-347 guitars.
Some Gibson literature notes that they were dirty fingers, but I’ve seen some that states they were Series VII “Super Humbucking” as well. The resulting confusion is expanded from the fact that only one set of screw poles is visible on the 347. Since the ES-347 came with “tar-back” (epoxy potted) humbuckers, it’s been hard to prove what the construction is. It seems like the conventional wisdom is that they are indeed Dirty Fingers, because the DCR measurements are 16 Kohm. My personal experience with known and unknown Dirty Fingers was this: I have owned a couple Gibson 335s guitars with the classic open bobbin, 12 screw pole configuration. I’ve also owned a couple of ES-347s with the 6 screw, covered configuration. To me, these two different styles of Dirty Fingers have always sounded quite different. The ES-347 style (I’ll call these 347 DF herein) has always sounded much darker than the classic open bobbin 335S style (335S DF). For a while, I had a pair of pulled 347 DF’s that found their way in and out of a few different guitars and was never happy with the results. In all cases, they never had the clarity and detail that the 335S DF had. They also never seemed to be as hot as the 335S DF, despite the same 16 Kohm DCR. When I found a dead 347 DF on ebay, I grabbed it in order to rip it apart to see what was on the inside.

The Dirty Fingers Design
The dirty Fingers was a big departure from traditional Gibson pickups of the era. While it looked like a standard humbucker (except for the 12 screw-pole version), it was quite different under the hood. The DF used 6000 turns per coil of #44 wire, leading to a coil DCR of about 8 Kohms each (16 Kohm total). Additionally, it used a less common 3 ceramic magnet design with ns-sn- ns orientations. This is not dissimilar to the two-magnet construction with opposing sn-ns polarities in a P-90, but with an extra magnet for the second coil. I’ve read that the Lawrence designed “Super Humbucking” pickup may have used three ceramic magnets too, but I can’t confirm this. I’ve also read that it only used one magnet. What is clear is that the “Super Humbucking” has a total DCR of about 6.5-7.5 Kohms. As such, the distinguishing feature of the Dirty Fingers pickup to me is the hot #44 windings that it got (16 Kohms).
From http://gibsonguitarmuseum.com/05_electric_spanish/model04/01.htm
The ES-347 TD offers a sound with more brightness and sustain than the other guitars in the series. This additional brightness and sustain (as compared to the ES-335TID) was primarily achieved by mounting the bridge on two 5/8" brass studs and adding a brass fingerboard nut. In addition, the two Series VII Super Humbucking pick-ups have one Indox V and two Indox VII magnets per pick-up contributing to high output. As with the ES-335TD, it has the Maple center block and the coil tap switch for the flexibility of either Humbucking or single coil tonality.8
I’m not sure what the source of this information is, but it does suggest that Super Humbucking pickups were used, and that they were 3 magnet pickups. It does read like an official Gibson datasheet, but I can’t be sure. Again, I think the final word that early ES-347 were DF’s lies in the DCR measurement.

The attached PDF has photos of the Dirty Finger being ripped apart.

Gibson ES-347 dissection.pdf

Here's a few other 3 ceramic magnet humbuckers:

[EFK]

That's all really interesting. Not that I'm a fan of the Dirty Fingers, but it's cool to see a lot of documentation surrounding all that, so thank you for posting it! And maybe you should indeed save it all to save the trouble because I have no doubt it will come up again; there is a LOT of mystery/confusion around mid 70s through early 80s Gibson pickups experiments.

[PoorMan]

Client found the baseplate and shipped it to me. This one is nickel silver.

There is some solder on the side of the leg so it appears it was grounded somehow.

[EFK]

Solder on the side of the leg might mean copper shielding tape around the bobbins. Velvet Bricks had copper tape around the bobbins and then a strip run down the side of one leg and soldered there to the baseplate.

[Stratz]

None were 16k except the Dirty Fingers. But they had the Super Humbuckers, which was a name they used for a bunch of different pickups such as the Series VII, but they are 6.5-7.5 Kohms. The hottest of those I have seen was about 13-14k.

Interesting....I found 2 sets of Dirty Fingers from the early to mid 80's in one of my junk boxes.
One set has two rows of screws and the other set is a traditional screw/slug style. Both have nickle silver base plates and neither had covers from the factory.

[David Schwab]

Interesting....I found 2 sets of Dirty Fingers from the early to mid 80's in one of my junk boxes.
One set has two rows of screws and the other set is a traditional screw/slug style. Both have nickle silver base plates and neither had covers from the factory.

I think they only did the covers on the ES-347. I don't think they made that model very long.

[PoorMan]

I'd just hot-glue...

I think hot glue would hold well (a concern since it broke off once), but it might be too thick and leave a witness line. I'm trying to keep it as original looking as possible. Maybe I should rough up the glued surfaced to promote more "bite" in the adhesion?

I imagine CA glue would be too brittle and weak. I could use slow cure black epoxy and maybe bury the entire back of the pickup in more black epoxy...but then I might clog the fillister screw holes (wonder how they avoided this at the factory???).

The existing epoxy has a very dull finish. Maybe from age, but it doesn't look like shiny new black epoxy. That's another concern in maintaining the original look.

Suggestions?

[David Schwab]

You have to repair the pickup. No one is going to be looking at the bottom when it's in a guitar. Are you putting on a baseplate? Just glue it on with 5 minute epoxy. Or are you putting on one of those bars that has the mounting holes?