Tarback Pickups

[Zhangliqun]

Guy sent me some tarbacks from an L6S to see if I can fix/rewind them.

a) Is there a reasonably safe way of getting in there that doesn't involve explosives? (He opened up one of them and damaged the ends of the bobbins pretty badly.)

b) They don't come with standard baseplates -- they have a mount bracket no wider than the legs that seems to be secured only by the tar. I'm thinking I'll tell him that I need to remount the bobbins/magnets assembly on a standard plate but is there a way to get these scrawny plates back on there?

[big_teee]

Check out post 9.
http://music-electronics-forum.com/t39746-2/

[Zhangliqun]

As daunting as I thought. It's not clear in the notes (or maybe my reading comprehension is symptomatic of early onset Alzheimer's) but did he just reheat the epoxy to get the brass mount strip back on?

[LtKojak]

As daunting as I thought. It's not clear in the notes (or maybe my reading comprehension is symptomatic of early onset Alzheimer's) but did he just reheat the epoxy to get the brass mount strip back on?

If those p'ups were the epitome of heavenly tone, I could understand going the extra mile to try to save'em but, as this not being the case, the owner will be much better off with any of your p'ups, David.

Just tell him I said so!

[SonnyW]

As daunting as I thought. It's not clear in the notes (or maybe my reading comprehension is symptomatic of early onset Alzheimer's) but did he just reheat the epoxy to get the brass mount strip back on?

I'm the guy that did that rewind that big_teee linked to my description of. The answer is no on reheating the epoxy. I used new bobbins and new slugs and fresh epoxy. I re-used the cover, magnet, keeper, and screws and the brass strip. I did leave a little of the original epoxy on the brass strip, just so it would look kind of the same as it was originally, but it is held in by new epoxy. The bobbins aren't mounted to anything like a baseplate, just held in place once in the cover by the epoxy. That is also true of the brass strip. I did use double sticky tape to hold the bobbins in place in the cover. I also used some black banker's wax for that as well. I took the first one on as a challenge, because it was for a very good customer, and the second one only because of value of the guitar it was from. But unless this is for restoring a valuable guitar, (which an L6S might be), it isn't economical as a rewind. It is not a problem that the owner has damaged the bobbins, they have to be replaced anyway. But there is a good chance of breaking the magnet and that would be very bad. Getting the epoxy out by chiseling with a hot soldering iron is extremely tedious. Based on my experience of doing two of these. I would agree with LtKojak's recommendation.

[Jim Darr]

... I also used some black banker's wax for that as well...

Sonny,

What exactly is "banker's wax"???

Jim

[SonnyW]

Sonny,

What exactly is "banker's wax"???

Jim

It is a hard wax that is a lot like the old sealing wax. It is also a lot like jewelers "dop wax" that they use to hold gemstones for polishing. Opticians also use it. Sealing wax would work as well and the color doesn't matter. I just happened to have some of it around that I inherited from my dad's jewelry shop. Any kind of relatively sticky wax would have done the job of holding the bobbins in place, I just used it mainly because it was black. I also didn't want too much of the epoxy to get in between the cover and the bobbins and leak out. My epoxy, which I also already had around that I use for lots of other stuff is kind of thin and runny and I was afraid it would run and leak out. So I put the bankers wax around the bobbins as a seal and to keep them from floating around and also so I wouldn't have to use as much epoxy.

Edit: I found a link for some of it here:

http://www.nostalgicimpressions.com/...Wax_p/199h.htm

[Jim Darr]

It is a hard wax that is a lot like the old sealing wax. It is also a lot like jewelers "dop wax" that they use to hold gemstones for polishing. Opticians also use it. Sealing wax would work as well and the color doesn't matter. I just happened to have some of it around that I inherited from my dad's jewelry shop. Any kind of relatively sticky wax would have done the job of holding the bobbins in place, I just used it mainly because it was black. I also didn't want too much of the epoxy to get in between the cover and the bobbins and leak out. My epoxy, which I also already had around that I use for lots of other stuff is kind of thin and runny and I was afraid it would run and leak out. So I put the bankers wax around the bobbins as a seal and to keep them from floating around and also so I wouldn't have to use as much epoxy.

Edit: I found a link for some of it here:

Wickless Traditional Bank of England Sealing Wax

Sonny,

Thanks for the detailed explanation. Sounds like you thought through the Tar-Back rebuild very carefully and executed it with precision. Your use of Banker's Wax was very clever. I'll I have add it to my "bag of tricks"!!

Thanks again for sharing and your post.

Jim

[Jim Shine]

I have had luck with using mineral spirits or denatured alcohol. It depends on the epoxy, but those two solvents usually do the trick. Submerge and let soak at least over night. With some epoxies it will become rubbery and you can peel it off. Others tend to get soft and crumbly. You will be able to break off pieces in chunks until you hit an area not affected by the solvent. Then you have to resoak.

[Zhangliqun]

I'm looking at cutting it out with metal wheel on a dremel. Any thoughts on that?

[mr fab]

I wonder if the epoxy can be cut with a hot knife. does anyone know?

[David King]

Heat is the best way to deal with potting epoxy, a heat gun will turn it rubbery and crumbly to the point where you can just pick it apart gently. A temp of 170-180F is all you need. A dip in boiling water will do it as well as long as the water won't harm the innards. If it starts to smoke, don't breathe those fumes as they contain amines that will irritate lungs etc.