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2 weeks ago I wound 10 strat pickups to 6.5k. Last week I checked the resistance again and it had gone down on all of them. On most of them the resistance dropped by about .3k. Today I checked again and it doesn't seem to have dropped off any more. Is it normal for the resistance to drop like that? or is it more likely to be that my DC meter has malfunctioned or I got a spool of bad magnet wire?
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Temperature plays a big part. They will read higher the higher the temp is. Used to really confuse me. Were they wax potted shortly before the first reading?
-Stan -
When I took the 1st reading it was right after winding them. They were in my basment that is 60 degrees with 65% humidity. After I took the 1st reading I wax potted them and put them in a room that is 68 degrees and it usually sits at around 30% humidity. Could the humidity change things?Comment
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Possibly. Perhaps there was heat generated by the winding process also...I usually let mine sit for 10-15 minutes before checking.
-StanComment
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Hi Guys, I know on most every pickup I wind I get a .3 drop after sitting a while, sometimes it goes up a bit after potting and cooling due to some tightening by the wax on the coil, but yes after winding when the coil settles all of mine drop about .3. Another thing I noticed is that if my fingers are touching the probes when I check resistance it also throws it off by .3 as well, try it with touching both probes with your fingers while checking and without and post the results, im curious if it is just a freak of my meter or is it supposed to do that??Comment
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That makes me feel a lot better, thanks guys. I have never seen the resistance in my pickups drop before so this had me a little worried. I've already shipped 4 sets of pickups off that spool of wire and I would hate to have to recall them. I still think I'm going to switch to another spool of wire and hold on to the 10 pickups I've still got just so I can watch them and see what happens.Comment
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Here's another angle that quite often happens. You made a slight change to the tension on the wire. Funny things happen when you stretch the wire and will show a consistent false reading if you are fixing the tension.sigpic Dyed in the woolComment
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Do you mean that because we use tension, then if the coil settles and the tension because less the DCR will go down?Comment
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They will measure much higher right after winding and 0.3k is not out of the question for a 6k+ wind. You need to let them acclimate to room temperature before measuring the resistance. A couple of degrees here/there from room temp will have only a minor effect, but handling them for a few minutes will have a significant effect unless you're winding at room temps near your body temp. Heat generated due to friction in the winding process impacts the reading as well, which may be what you're seeing here.Originally posted by corduroyew View Post
Copper has a positive thermal coefficient, which essentially means the resistance goes up as the temperature goes up. I'll leave it to the more detailed folks here for the in-depth analyses. Best to let them rest an hour or so at least before measuring for accuracy.Comment
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Well, things can happen to the insulation of the wire and tiny shorts can occur.Originally posted by corduroyew View Post
In any case 0.3 K Ohms difference is a gnat's dick when it comes to whether you can hear it or not. It's most probable that the cause is a change in temperature as others have mentioned.sigpic Dyed in the woolComment
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Another vote for the friction of the winding process, especially the friction from your tensioner, which for some is a mechanical device but for others (like me) is just the thumb and index finger.
I don't have a turn counter so I go by DCR but am careful to factor in temperature of the room and tensioner friction when taking measurements along the way, which basically means I shoot for a slightly higher DCR on finishing the wind so when it cools down to room temp (+/-72 F) it pretty much hits the nominal spec.Comment
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