Dumb question. How do you read pup output?

[XOSKELETAL]

Same question.

 

[Tonefiend]

Get an volt/ohmmeter from Radio Shack or the equivalent. RS is not the best but cheaper than a new Fluke. Digital is the most accurate and easiest to read. Analog is pretty tough to get a good number. Set it to 1k Ohms. Put the read lead to either hot or ground of the pickup, then put the black lead to the other one.

 

[XOSKELETAL]

So, do I have to disconnect wires from the pup, then?

 

[Tonefiend]

No the wires need to be left on the pickup. Just unsolder them from the guitar.
You can pull readings from fender pickups right off the bobbin where the leads are soldered. But gibsons are off the ends of the pickup leads.

 

[BrianGWN]

I hate to split hairs folks, but what was described in the responses was how to measure the DC resistance reading of a pickup. The original question asked about how to "read the pickup output". It may have been the intent of the person asking the question to really ask how to measure the DC resistance, but I would like to offer a reminder that it is really not appropriate to mix the two phrases.
A pickup's "DC resistance" versus it's "output" are two different beasts. Measuring a pickup's output would be a rather fuzzy arbritrary procedure, output would be a voltage probably in millivolts. The resistance reading of the pickup does give us an important clue as to how the pickup likely behaves and it's relative output, but it is not THE OUTPUT. The magnet strength and the coil wire gauge are other important factors that determine the output.

If you want to get an accurate reading of the resistance of a pickup, yes you should disconnect at least the main hot wire of the pickup from any volume control.

Sorry to rant, the regulars around here probably know all this stuff, but the newcomers could get messed up.

 

[mikeslub]

A lazy, probably not real accurate (but close enough) way to check the DC resistance without removing the pickups from the guitar is to simply make sure your volume controls are on "10", pickup switch not in the middle position (put in rhythm or treble settings depending on which pickup you want to check), and touch the lead ends from the meter to the ends of the phone plug running from the output cable from the guitar.

 

[NBlair930]

Mike,
What is the marging of error in the "Lazy Method"? Seems a lot easier for a couch potato like myself.

 

[BrianGWN]

The quick short cut method of checking the resistance using a standard guitar cable with the volumes on 10, as describe by Mike, is fine for getting in the ballpark. It would do to distinguish whether you had something like a '57 Classic traditional pup versus something like a 498T or 500T.

In the short cut method you are measuring the resistance of the volume pot in parallel with the pickup, so the reading is lower than the actual reading of the pickup alone. As to the error, here are some sample numbers: If you had a 500K pot and an 8K pickup, the measurement would read 7874 ohms. Going the other way if the measurement was 8K with a 500K pot, the pickup would actually be 8130 ohms.

The error with a pot somewhere around 500K and a pickup somewhere around 8K would be somewhere around 125 ohms. There is no way to know the exact amount of error without knowing the value of the volume pot, and those tend to have a value with quite a tolerance. The only way to know the pot value would be to disconnect the pickup from the pot to measure it, but then you are back where you started trying to make a simple measurement without undoing connections.

 

[blackdog]

Error margin,

Let's see...

Let's take a worst case of having a 250K volume pot (on 10, of course), and a particularly "hot" pickup of, say, 16K DC resistance...

With the lazy method you would read 15.04K, about 7% error.

A more common case of a 500K pot and an 8K pup would read 7.87K, which means 1.6% error...

Now there's no way of figuring out the value of the volume pot unless you disconnect the pickup.

Connecting the meter leads to the output cable of the guitar you can read each pup and both in parallel just by switching them with the toggle.

L.

 

[XOSKELETAL]

Great White, my intention was unintentional (huh?). I don't know dick about all this DC resistence/output stuff, but I thought it would be cool to check the pre-PAF stickers on my 57 GT. But, I'm unlikely to start disconnecting wires and soldering and stuff. All the references to 7.5, etc made me curious. Thanks for the lesson.

 

[Ed Rafalko]

I've tested the Lazt Way. It's a lot more accurate than you guys are saying it is. I have a Duncan Distortion that read 16.63K resistance on my meter before I put it in the guitar. After I put it in the guitar, using the lazy method, it read 16.61K, for a difference of .02K, or about .02 of an ohm. The pot measured to be 524K. I tend to check thngs before and after, and every time I've checked the readings on pickups before and after installs, they seem to be within a couple hundredths of an ohm.

 

[hogy1]

While we're being anal retentive...
.02k Ohm is not .02 of an Ohm, but 20 Ohms. 1k Ohm is 1000 Ohms.
Not that it makes a bit of difference, but...
hogy

 

[Ed Rafalko]

Duh... I'm an idiot. Hogy's correct. As always.
Hogy, be prepared to be invaded sometime soon.

 

[BrianGWN]

Hmmm, if you do the math a 524000 ohm pot in parallel with 16630 ohm pickup should produce a reading around 16118 ohms. Going the other way, if the reading really was 16610 with the same pot the pickup would have to be up around 17153 ohms. As we know the pickup resistance reading will drift up if the ambient temperature increases. Maybe you installed it and did some wailing on that guitar or had it sitting under some lights, and managed to warm up the pickup before you made the after-installation measurement.

The math doesn't lie, but at the same time there is a fair amount of Murphy's Law going on here, temperate changes, funky meters that may read differently depending how long they have been on warming up, whatever... The point is that the reading of the pickup while connected to the volume pot should be a little lower than the true value, ALL other factors remaining constant which may be a dubious assumption...