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Rule or Rules of Thumb?


 
7/22/2003 9:15 PM
Jeff G.
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Rule or Rules of Thumb?
Well, I wound up another Humbucker last weekend. I thought I'd kind of figured out a rule of thumb for resistance per turn. I got relatively close to my desired DC resistance by winding strictly to a number of turns, but was off overall (low) by 200ohms. That's a bit more than I would have thought.  
 
Anyway, I'm using 42 gauge single-build plain enamel wire. I'd estimated about 0.8 ohms per turn, realizing that it's lower to begin with and will increase as the diameter of the turns increases. Using this number, I simply wound each bobbin to a certain number of turns and put the pickup together (pretty cocky, eh?). When I measured the overall resistance, I noticed it was low, which makes me wish I'd measured each coil.  
 
Anyway, is there a rule of thumb that would have gotten me closer to my desired value?  
 
Is this simply the effect of scatter winding ... oddball winding shapes, hence widely varying diameters?  
 
The good thing is, the pickup sounds fantastic! I better get in there and measure the individual coils!
 
7/23/2003 2:23 AM
Jason Lollar
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The rule of thumb is to start up a chart with turns and resistance for different types of bobbins. Takes time to collect enough data but it gives you some places to start.  
You are usually safe to bet on 6 string bobbins that the ohms will be less than the turns! Alot of it depends on the coil shape and size, wire tension and actual wire dimension, oh and ambient temp and if you goofed something up or not.  
The only way I know how to wind to a resistance is to sneak up on it.
 
7/24/2003 1:10 AM
Jeff G.
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I'm keeping records (need to be sure to measure individual coil resistance each time though), but my database is only three so far ;0  
 
I think I can see now how the old PAFs might have varied a lot from pickup to pickup.  
 
Do you normally wind to a certain number of turns unless someone wants a specific rewind?  
 
It's a bit of a pain measuring along the way. I broke a wire on my second PuP and had to repair it to continue. It sounds good though ... just got a little heavy handed with the 600-grit sandpaper.
 
7/24/2003 6:06 PM
Jason Lollar
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I used to wind to resistance because that was how I was taught, took longer than it should have to realize it was futile so anymore I think in terms of turn count. Sometimes you have to transfer ohms into turns dealing with coils of an unknown spec. Sometimes if its shorted out and its a one pickup instalation where you cant get a good ohm reading off the other coil you have to take a guess by coil size and hopefully having seen other examples similar to it you can guess at a turn count and come pretty close.
 
7/25/2003 11:12 AM
SK
I use the .8/turn for 42 rule of thumb, also 1/turn 43 and 1.2/turn 44. But they are just starting points. Besides all of the factors in winding I have also had wire that just didn't meet spec. I had a spool of 42 that somewhere in the middle for about 5 pickups worth went low on DCR. I use a counter primarily, rules of thumb for conversions/ starting points etc. I know the wire was off because I was winding similar pickups to similar turn counts...
 
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