Intermittent coil in Custom...

Chad

New member
Okay, this is about driving me crazy. Long post ahead.

Last night I put a genuine Duncan gold cover on a TB-5 Duncan Custom. Wow, it was a tight fit. A covered TB pickup is so gigantic that I had to trim away some of the mounting ring on my Explorer.

Anyway, I get it all hooked up and it plays fine last night. I plug in today and it's very thin sounding. Sure enough, I measure and I'm only getting about half what the normal reading should be.

So I took the pickup apart. I've owned several SD pickups and this particular one had some of the gooiest, most disgusting tape I've ever encountered. When I've changed mags in this pickup in the past, I've had to clean up thoroughly with lighter fluid because black goo gets everywhere.

So I completely removed that tape and cleaned up all the black goo. In the process some of the scotch-style tape that covers the coil-to-lead wires came loose. So I cleaned up and shrink wrapped all of those.

At some point, I discovered that pushing on the edge of the treble side of the slug coil would cause the reading to bounce back and forth between half and normal reading. I pull off the coils to inspect. Everything looks okay. In the process, a lot of the wax comes loose and I must have spent 30 minutes trying to get the coils level. I ended up having to remove/scrape a lot of the excess wax to get them even and level. I might have to re-pot the pickup at some point.


So it stays at the normal reading. I push and wiggle and it won't budge form the normal reading. I put the pickup all back together, put on new tape, put the cover back on, put it in the ring, re-mount and re-soldered it back into the guitar. DURING EVERY STEP OF THAT REASSEMBLY PROCESS, I kept a meter on the pickup and it stayed proper the whole time.

So I play it for 10 minutes and all is fine. Then it drops back to half reading. I have spent almost all morning dealing with this and am looking for help.



Any ideas what is going on? I'm wondering if the overly tight fit of the cover cut part of the wind and it is connecting and re-connecting. Is that possible with wire that small? Perhaps the coil wire that connects to the wind is loose.

I'm probably gonna take it all apart, then gonna have to pull off the copper tape that covers the slug coil and inspect. But gonna take a break from it for now and hope to get some input from you all.
 
Last edited:
Re: Intermittent coil in Custom...

I doubt that it is a broken wire in one of the coils or you'd get a reading somewhere above 1/2 the series reading (like a tapped coil). The fact that it is just 1/2 (which I presume is about 7k) tells me that the problem is at the wire at the end of the coil which is attached to the colored hookup wire. Sounds like it is either not a good connection and comes apart (electrically) or that it is not insulated well and is shorting to ground.

I would first check the integrety of the connection. The wire has a coating on it that should be carefully scraped off in order to get a good solder connection. Make sure you are using a very thin rosin core solder or a non-acid flux.
 
Re: Intermittent coil in Custom...

Here is a vid that better explains what I'm dealing with:

 
Re: Intermittent coil in Custom...

Also, wondering why this has happened? I used this method to install the pickup cover:




When I was done, I went over the finished pickup with a heat gun to get an even wax spread. Could that have loosened the wind/coil wire connection? Seems unlikely. This pickup has worked perfectly fine for several months throughout mag swaps and so forth.
 
Re: Intermittent coil in Custom...

Okay, I got the copper tape pulled off. Now, it appears there is another layer of orange-something. Don't see how to get past that. Beginning to wonder if this pickup is destined for the trash can. Or perhaps a donor to a hybrid pickup since it has one good coil.
 
Re: Intermittent coil in Custom...

Still looks to me like it's the coil wire attached to the hookup wire (either the black or the white). But you've got your hand in the way so it's all covered from view. Why did you do that? You spend the time and effort to make a video, but cover it all up with your hand so we can't see what's happening.

I'd take those connections apart, clean and resolder (as I suggested in my previous post), and test again before retaping or shinkwrapping.
 
Re: Intermittent coil in Custom...

Sorry about that. Video took one minute to shoot. Goal of it was just to show how the problem was isolated to the coil itself and how slight movement to the top of the bobbin caused the meter to jump. Beyond that, I didn't really know what to show (why I'm asking for help). Also, the copper tape was covering the wind, so there really wasn't much more to show anyway.

Since the vid was shot, I have removed the copper tape that surrounded the coil. I'm guessing the problem area is where the jumper wire (black and white wire between wind & output lead) connects to the wind. But after I pulled back the copper tape that surrounds the coil, I found that the wind is encased in some sort of orange material, so I can't get to the jumper/wind connection point. Any ideas?
 
Last edited:
Re: Intermittent coil in Custom...

Anybody know anything about that orange material that encases the coil? Or any other thoughts?
 
Re: Intermittent coil in Custom...

The connection point from the one coil to the other is loose.

To be more precise: the leads that correspond with the red and white are not well soldered.

That's it.
 
Back
Top