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Pickup Values Don't Make Sense.


John Abbett
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the 7k is probably the neck pick up and the 14 k the bridge

the bridge is wound hotter so it will be more balanced when you are switching between bridge and neck.

edit i may have that backwards any way one is the neck the other is the bridge pickup.

Edited by Tim37
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You have it right Tim. Bridge is higher output to balance with the greater string vibration at the neck pickup.

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The string vibration is much more pronounced in the neck position...simple physics...so the pickup needs to be less powerful to pick it up...

usually though,it is more like 14k/10k...but it is not uncommon to have a 7k in the neck,and a 10k in the bridge,at which point a "rock and roller" or "metal guy" such as myself will switch out the bridge for a hotter one...

They also get weaker with age...

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If they are 4 conductor cables you may well have them wired wrong so a coil is shorted or "split" (ie only half the value) or you may be reading the lower one in parallel or something. Test each coil alone to see that all are working properly.

It is true that a neck pickup often is less than a bridge although a lot of gibsons and early pickups were identical and this discrepancy is too much and the 7-14 ratio looks suspiciously like a shorted coil to me.

pete

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I think maybe one is shorted. What doesn't make sense to me is that I thought the orginal values were 7.8 and 9.0. Now I have 7.8 and 14. something. I'm guessing the 14. something one is shorted. What I don't understand, is if it was 9.0 and shorts, shouldn't it have less resistance, not more? Less wire means less resistance right?

I did get the pickup hot. I dribbled a very small amount of solder on the joint of the pickup cover and the bottom of the pickup because it was loose and wouldn't stay put. I didn't heat up the pickup, just dribbled. I must have screwed it up. I just don't understand the physics here.

I learn all the lessons. Sometimes twice.

-John

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If a pickup shorts, it will read a lower DC resistance or a total short of no resistance. The only way I can think of for the DCr to go up would be if a wire broke and the pickup read infinite resistance.

Remember that DC resistance is not the only factor in pickup output. :D Perhaps the "overwound" pickup has weaker magnetism. Who knows.

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Do you have a guitar you can put them in to test them? If so, you can always find out which one is not right, if any... Also, I think the resistance can increase if there is damage to the wire somewhere that did not cut the wire completely, but damaged it somehow.

Where did you get the pickups from? Maybe they can answer any questions about what the pickups should read in terms of resistance. If you bought them as a set, maybe one of them is simply the wrong pickup. Handling mistakes do happen. I'd suggest getting in contact with the seller.

Heggis.

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  • 2 weeks later...

Yes...it does sound like the value of half a coil. If the cover got heated it could have melted the insulation on a wire and shorted a coil and give you a near exact half reading like this...or testing the wrong combination as south suggests. If 4 conductor...try testing pairs and you should be able to tell if you have a short of one coil and the value of each. Adding them together should give the total resistance.

Remember that DC resistance is not the only factor in pickup output. wink.gif Perhaps the "overwound" pickup has weaker magnetism. Who knows.

This is kinda true...I was involved with a problem recently with a pickup that was custom made by seymor ducan...a single coil of 14K!!! It was giving no output and also used for a new sustainer coil...which didn't work. As I am on the other side of the world and this was a prototype troubleshooting it was going to be a problem and we tried everything. Turns out SD jnr didn't magnetize the pickup at all! No wonder no output or sustain from the thing! Remagnetising with rare earth magnets brought everything back to life...but it took a while to discover the problem!

Pickup magnetism will not change the resistance of the coil...only the number of turns will do this...so in the above example, it read 14K but had hardly any output at all. More magnetism will normally add power, but eventually will dampen string vibrations and even put out intonation and tuning by the pull on the strings. The amount of 'metal' in the core will also have a big effect...it is a matter of inductance.

The coil resistance is a primitive and effective measure of the state of the coil though. The magnets will not be causing these reading problems. It is also unlikely that such a big difference between two possibly identical pickups will be the problem. A recent stew-mac email had some tips on opening a cover and securing it, and this might be necessary...it could be something fairly simple in there.

pete

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Also, I think the resistance can increase if there is damage to the wire somewhere that did not cut the wire completely, but damaged it somehow.

I think if this were the case, you wouldn't get a consistent DCR reading. It might go between 0, 14k, and infinity. That would be a sign of an intermittent short.

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Good point..check the battery and leads...

If you do take them apart Stew-mac sent an email tip sheet recently that showed a neat way of opening the cover. Slide a razorblade gently through the solder joins...I'll be trying this next time instead of the solder wick method I usually use.

While you are in there...you might consider wiring them as four conductor since you will likely need to test each coil anyway. Start with the low value HB as this is likely where the problem lies if there is one.

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