humbucker turn count vs resistance

[mkat]

I've wound a humbucker for a bass, consisting of two single coils. Both have the same turn count, or so I thought (using a counter), but have different resistance. One of the coils is around 0.4k higher than the other. Is it adequate to wind down one coil to get the same resistance or isn't it worth the trouble?

Regards,

Michael

[David Schwab]

If your readings are way off, you might have a short. If you are sure you don't have a short, I wouldn't worry about it. My two coils never read the same, but it's usually in the 10's.

[NightWinder]

It can be simply one coil is hotter in temperature. You should let them settle overnight to get a good reading. You'd be surprised.....breathing on them will raise the dc 10...maybe even .20 or soo.

[mkat]

If your readings are way off, you might have a short. If you are sure you don't have a short, I wouldn't worry about it. My two coils never read the same, but it's usually in the 10's.

No short.

[mkat]

It can be simply one coil is hotter in temperature. You should let them settle overnight to get a good reading. You'd be surprised.....breathing on them will raise the dc 10...maybe even .20 or soo.

Yeah, I noticed that actually. It's really cold here tonight, still winter. The first reading straight after I wound it was a .5k difference, followed by a .4k difference 30mins later. I'll check again tomorrow.

[mick]

Don't worry about it , if you are hand winding you are going to have slight differences here and there , even with machine winding you will get slight differences from pickup to pickup , coil to coil etc ...there are too many variables to be 100% accurate , set yourself a tolerance and as long as you are within it they should be fine..

Mick
Brierley Guitar Pickups
Adelaide
Australia

[Spence]

400 Ohms is a gnat's dick in terms of how much difference that's going to make.

[Possum]

tension....

you may have stretched the wire on one coil , that would account for the difference too.....still I would suspect a coil short, if it was me I'd wind it over....

[David Schwab]

400 Ohms is a gnat's dick in terms of how much difference that's going to make.

I'm never that far off, and I don't always stop the winder at the same number. I'll be off maybe 60 Ohms.

The one coil I had that read about 500 light tipped me off to a short, and I realized I hadn't taped off the steel blade that I wind onto.

In my case 500 Ohms is almost half of the total resistance of the coil!

[mkat]

Thanks all, for your replies and suggestions. I rechecked the readings tonight, which now have a difference of 27ohms.

[Joe Gwinn]

Thanks all, for your replies and suggestions. I rechecked the readings tonight, which now have a difference of 27ohms.

The temperature coefficient of copper is 0.0039 per degree C.

Let's do a little example. Say one has a coil that measures 10,000 ohms at 30 C. Later, in the night, the temp drops to 25 C, for a 5 C change. The resistance will drop by (0.0039)(5)(10000)= 195 ohms.

The temperature during wax potting is about 150 F, or 66 C, so the drop to room temperature at 20 C is 46 C, and the change in resistance is (0.0039)(46)(10,000)= 1,794 ohms.

So, let your pickups cool well.