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Copper tape effecting inductance or DC ohms readings etc


 
5/24/2006 2:34 PM
GTarman Copper tape effecting inductance or DC ohms readings etc
I saw a post here about certain tape causing funny things to happen to readings on coils because it was conductive etc.. I was just looking at A seymour duncan humbucker and both coils are wrapped in copper tape and grounded to each other by a short wire and solder. What about this deal? Maybe we can delve into this deeper and see what gives. Since most posts here dye after about 1 day, Lack of intrest or no one comes here anymore?
 
5/24/2006 2:54 PM
Spence
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Just clearing my desk when I spotted your lone thread....  
 
The other tape you're thinking of was black photographic masking tape which has traditionally been used in wrapping humbucker coils. Not wishing to Dis Dave who's thread it was, he must have had something else going on there. The coil wire has it's own insulation so it seems like he has lost some of that insulation for the tape to effect the resistance.  
 
In the case of the Duncan you're talking about, the copper is there to act as a shield against 60 cycle hum. Copper foil has an adhesive backing. The copper is always connected to the ground of the pickup. What it can effect is the pickup's inductance and magnetic profile.  
 
Lock up behind you......
 
5/24/2006 4:33 PM
GTarman
Thanks Spence. I did notice when I took of the copper tape and measured the coil ends where there are soldered to the leads the resistance actually went up by .08 ??Now i'm really miffed.
 
5/24/2006 7:47 PM
Dave Stephens
Actually there was nothing else going on in the P90s that would allow that tape to have such an effect. The DC resistance readings on the tape was the highest I've ever seen in conductive tape, just miles more than the Stew Mac tape. Stew Mac tape's resistance is so high it probably doesn't have any effect. It was MWS wire wound looser than tighter. No coil shorts, Thats why I started that thread, I was very alarmed that some were saying this was the tape the Seymour uses but obviously its not. I didn't realize that simple tape could have such a huge effect on a coil. The MWS wire is very well insulated. I have some Korean stuff if you wind it very tight at all it shorts out the coil, really bad stuff. Copper tape can be a good thing if you want to trim some treble off a pickup, maybe thats the real reason Duncan used it, its an audible difference. I'm experimenting with that idea on one pickup right now. I wonder if its really necessery to ground the tape?
 
5/24/2006 8:07 PM
Joe Gwinn
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Re: Copper tape effecting inductance or DC ohms readings
On 5/25/2006 1:47 AM, Dave Stephens said:  
quote:
"Copper tape can be a good thing if you want to trim some treble off a pickup, maybe thats the real reason Duncan used it, its an audible difference. I'm experimenting with that idea on one pickup right now. I wonder if its really necessery to ground the tape?"
Yes, or the presence of the tape will greatly increase the hum. The ground connection doesn't have to be all that low a resistance to prevent electrostatic noise, but it needs to be grounded nonetheless.
 
5/25/2006 6:15 AM
Dave Stephens
You know I wondered about that on blade pickups, I don't ground my blades and I can't hear a difference in hum either way, but also blades pickups are not wound with alot of turns either. I'll have to experiment with grounding the copper foil to see if it makes any audible difference for real....
 
5/25/2006 7:23 AM
David Schwab
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Re: Copper tape effecting inductance or DC ohms readings etc
On 5/25/2006 1:47 AM, Dave Stephens said:  
quote:
"Stew Mac tape's resistance is so high it probably doesn't have any effect."
 
 
Dave, which StewMac tape are you referring to? The two rolls I have, which I bought just a few weeks ago, are not conductive at all. Even putting the probes very close together gives me zero resistance.  
 
Is it an older brand they were selling maybe? The current black paper tape they sell is actually black paper, and the adhesive looks clear, or even a little whitish.
 
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