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Voltage meter readings

BrokenGstring

Member
Messages
23
I just got this digital multimeter. I was measuring The output on my pick ups on this Mexican Nashville deluxe telecaster. The readings are very high. The bridge pick up reads 13.32 and neck pick up reads 12.01. But when I go through the five way selector they look to be normal. The neck and middle combination reads 5.46. The middle pick up reads 9.91. The bridge in the middle combo reads 5.71. I’m kind of new to this and I don’t understand why the other two are so high output.
Can these readings be correct or is there something that I am missing ?
 

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Jeff Gehring

Gold Supporting Member
Messages
5,807
OK, hold up. First off, these are resistance measurements, not voltage measurements.
Secondly, the UNITs are important. IE, not 13.32 ohms, 13.32 thousand ohms.

So, next you need to consider the CIRCUIT, you are not able to measure ONLY the pickup coil by itself in ANY of the selector positions, since you are just measuring the resistance from tip to sleeve at the output jack.

So what is the circuit? Well, it's a Nashville Tele, so three pickups connected to a 5-way selector, the output of which goes to probably a 250k volume pot. The wiper of the volume pot goes to the output jack tip. We don't need to consider the tone pot, since we are checking the DC resistance only.

Make sure the volume pot is turned all the way up for your measurements. I am going to assume that was the case with your reported measurements. I am also going to assume a 250k pot value.

So, you got 13.32 k ohms when the bridge pickup alone was selected. That means that 250k in parallel with your pickup gives a 13.32k reading. Working that backward, the pickup winding should be about 14.1k ohms.

So, you got 9.91 k ohms when the middle pickup alone was selected. That means that 250k in parallel with your pickup gives a 9.91k reading. Working that backward, the pickup winding should be about 10.3k ohms.

So, you got 12.01 k ohms when the neck pickup alone was selected. That means that 250k in parallel with your pickup gives a 12.01k reading. Working that backward, the pickup winding should be about 12.6k ohms.

Just as an example, you got 5.46k for the neck and middle position on the selector. From our results above that should be 250k in parallel with 12.6k in parallel with 10.3k. Doing the math that should give a parallel combination of 5.54k, which is reasonably close to your measurement value.
 

Beauchamp

Member
Messages
98
First of all you are reading pickup resistance in ohms, not any voltage. It looks like the high readings are individual pickups and the lower readings are two pickups in parallel. You should look up this info online, there is a lot of info available nowdays!
 

BrokenGstring

Member
Messages
23
Dudes my head is spinning.
I really wish I could understand this stuff. I would sane a ton of cash.
Thanks for the reply. I’m gonna do some more investigating.
what’s in parallel mean?
 

Badtone

Gold Supporting Member
Messages
1,084
Dudes my head is spinning.
I really wish I could understand this stuff. I would sane a ton of cash.
Thanks for the reply. I’m gonna do some more investigating.
what’s in parallel mean?
Bottom line is you did the measurements correctly, and @Jeff Gehring was kind enough to do the math. In his text your actual pickup coil resistances can be found. Do a little Googling on how to calculate parallel resistance and all will be clear.
 

PewterCam

Member
Messages
46
Basically it’s all fine and would best to just put all the ohm readings aside and have fun playing.
 

treeofpain

Gold Supporting Member
Messages
7,050
WE all started where you are, so it's okay to have your mind blown. Just go slowly...and listen to Jeff! :)
 

Timtam

Member
Messages
2,070
Next time you have a pickup disconnected from a guitar, repeat the process. It's simpler to start understanding how to measure and what the numbers mean that way, with just one isolated pickup.

There are ways you can get useful measurements direct from the cable of an intact guitar, but you need to know a little more about what you are doing. As others have explained, you can get values that way which are "close" to those of each pickup, which may be enough to tell if a pickup is dead or not (and avoid opening up a guitar).

As you will read elsewhere, the resistance of a pickup ("DCR") is a crude measure. It doesn't tell you that much other than if the pickup is healthy or not (is its DCR what the specs say it should be, rather than say ~0 ohms or 'open circuit' ?) and a rather rough measure of its relative output.
 

VaughnC

Silver Supporting Member
Messages
17,712
Yup, you're just reading the resistance of the wire used to wind the pickup's coil with the resistance of the volume control decreasing the actual pickup's resistance due to its "parallel" loading.

You have to remember that any 2 resistances in "series" will add. So, for example, two 100 ohm resistors in "series" will result in 200 ohms total.
The math is: R total=R1+R2.

However, if you connect those same two 100 ohm resistors in "parallel", the total will subtract and the result will be 50 ohms total.
The math is: R total=R1*R2/R1+R2 (for two resistors).
For 2 or more resistors, the math is: R total=1/R1+R2+R3...etc..

Also, keep in mind that the resistance of a pickup winding is only one factor and doesn't really mean much unless all else is equal, which they seldom are.
 
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vortexxxx

Silver Supporting Member
Messages
10,125
You are trying to learn the hard way measuring with the pickups in the circuit. Since you are newish at this, try reading some pickups that are not in a circuit or installed. Keep in mind that 2 different pickups (let's say humbuckers) that measure the same are not necessarily going to sound similar. Lots of variables go into pickups and tone.
 

Ron Kirn

Platinum Supporting Member
Vendor
Messages
6,707
first.. never read the pup with it wired into the circuit.. just never... next remember the ambient temperature of the pup will impact the reading.. a pickup that has been sitting in a room cooled to say, 68 degrees, will read somewhat differently than the same pup that's been sitting in a room warmed to 74.. If it;s been sitting on a window sill, in the sunlight.. the DCR's gonna be way up there..

next, and I'm sure someone has mentioned this.. the DCR is indicative of nothing more then the overall resistance presented by a piece of wire about 1 mile long.. that tells ya nothing... There are a number of other factors that can be used to "sculpt" the pickup that cannot be read with a VOM.. yet result in substantially MORE sonic differences than a wide swing in the DCR..

And while the DCR can be indicative of a higher optput on very basic designs.. it's still not critically useful. For instance a pickup with a DCR of, say 6.2K does NOT have a sound that is exactly and repeatably, notably different from one with a DCR of 6.4, 6.8 or even 7.2 .. and in the real world the 7.2 can be of lower output than the 6.4..

Using the DCR to determine the output of the pickup is a misnomer to begin with, but to do so is like measuring the diameter of the rims on a car to determine how fast it will go..

r
 

jvin248

Member
Messages
4,885
.

+1 temperature changes the kohms of the pickup. There is a mile of hair thin wire wrapped around a pickup bobbin.

DCR is easy to measure and gives you a relative measure of output. Yes, there are many hundreds of details why it is not so (like wire diameter and even pickup building stretches and thins wire due to high winding tension), but the meters are common and DCR gives you a general sense of what a pickup will do. A classic Strat coil will be around 6kohms, classic Tele around 7k, PAF humbucker around 8k, P90 around 9k, high gain 'hot' humbuckers will be 12k-16kohms.

Magnet strengths will change actual output too. I have noticed that many Squier Affinities made in Indonesia (current Fender source) run around 4kohms bobbins with strong ceramic magnets so they give classic Strat tones but with less noise (more bobbin wire = more powerful noise antenna). Prior China Squiers used 6k or 7k bobbins with ceramic magnets and give 'modern' Strat tones for rock (set them further from the strings if you want lower output).

I would guess that your master volume pot or the middle blender pot (if your system uses that way) are bleeding into your pickup kohm measurements if you are seeing 12-13kohms across a pickup. If you want to see what they are on their own you need to unsolder one side of the pickup wires from the switch or ground and measure the pickups on their own.

.
 




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