Is this an acceptable way to measure a pickups output?

[SinnerBoy61]

I don't want to remove my pickups to test the leads, but I was wondering if I could take readings from the inside of the tele's control cavity. I tested where the hot lead was connected at the jack, and where the ground was connected to the volume put. Is this an accurate way? The numbers I got were certainly acceptable for pickups, but I don't know if there could be any sort of reaction to where the leads are soldered? I hope this makes sense...

Thanks :)

[jwells393]

Measure the output of the switch with respect to ground (the ungrounded outside tab on the volume pot. The reading you get will be a little less than the actual resistance of the pickup. The pickup and the volume pot are in parallel. The equivalent resistance is determined as follows:

Parallel R.jpg

As an example assuming the actual resistance of your pickup was 6 K ohms and the pots are 250K............ (6x250)/256=5.86 K ohms

[GTO]

You will get very close readings (still within the normal tolerance you would get doing the pup on its own) just by 'going in' at the jack. Just make sure all the knobs (if we can say that on TDPRI) are at max.

[SinnerBoy61]

what's the procedure for checking at the jack?

[BrianF]

Originally Posted by SinnerBoy61

what's the procedure for checking at the jack?

Just plug a guitar cable into your guitars jack use the probes of your ohm meter to contact the other end of the cables plugs' tip and outside sleeve (ring) which is the ground. The equation above still holds true for the pots which are still in parallel with the pickups. Of course if you have an Esquire...one position is pure pickup so the pots would be out of the circuit.

[0le FUZZY]

...Place yer VOM leads on the switch with the hot lead tew the tab where the P/U hooks on tew the switch and ground lead tew any true ground (pot back, switch base or udder metal which is usually grounded).

... Make sure the switch is in the neck P/U position when checking lead P/U and visa versa.

...This will onlee giff yew a raw resistance reading and knott a true impedance reading. Usefull onlee with the thought in mind that a higher resistance reading will giff a hotter P/U but will haff nuttin tew dew with final sound as compaired tew a lower raw resistance P/U with a different windin and/or mag-a-nutes.





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[eryque]

"Acceptable" depends one exactly what the goal is. If you need something accurate, no, though you'll be close. If you just need a ballpark figure, then yes.

If you want accuracy, do what Fuzzy says so the volume pot won't affect the measurement. You will, however, have the tone pot in parallel, which will affect the measurement. So if you want to be really accurate, take a few extra seconds to unsolder the connections for the hot leads.

[0le FUZZY]

You will, however, have the tone pot in parallel, which will affect the measurement.

...HUH?

...The P/U should be isolated from the circuit at the post on the switch where each P/U iss soldered onna standard wired TELECASTER like I waz suggestin.

[jwells393]

When I read FUZZY's first post on this matter I thought to myself "Why didn't I think of that?". That's better than my original suggestion. I too am a little confused about eryque's tone pot in parallel.

[eryque]

You sure about that, Fuzzy?

This:



Is equal (electrically) to this:



Which looks a heck of a lot like two devices in parallel to me. This assumes that if you turn the volume pot all the way up its resistance drops to 0, which they never quite seem to do.

[jwells393]

Isn't a capacitor an open circuit to DC. Don't you measure an open circuit when you put a ohmmeter across a capacitor?

If you measure the bridge pickup when the switch is set to the neck pickup, the bridge pickup is out of the circuit. Am I missing something?

Most of mine are wired similar to this.

.............

[0le FUZZY]

...WOW!!! now I haffa headache HEE! HEE!

...Whence I wire a TELECASTER I wire it li kiss and whence the switch is in the neck position there iss noe contact tew the hot side of the lead P/U from the pot.

...The ground is ground --- dead ground (back tew the amp)! Noe cap involved at all.

...Mebby I ain't sure but I should be.





0le FUZZY

[jjkurtz]

The tone pot wouldn't even be in the circuit as long as you do like Fuzzy said by switching to lead if you're checking neck.

[SinnerBoy61]

whew..now I'm confused...

so, desolder from the switch and check with the switch in the opposite direction of the pickup I'm measureing?

[jwells393]

so, desolder from the switch and check with the switch in the opposite direction of the pickup I'm measureing?

Nope ......... no need to unsolder. The rest is correct.

[GTO]

Have we agreed what will be the best ambient temperature to check the resistance at yet? I'd say absolute zero would be favourite for an accurate reading?

[SinnerBoy61]

Originally Posted by jwells393

Nope ......... no need to unsolder. The rest is correct.

Cool..and how accurate did we all determine this method to be?

[0le FUZZY]

Cool..and how accurate did we all determine this method to be?

...That depends on yer objective.

...If yew are inner-rested onlee in continuity (makin sure the P/U werks) this type of hook up will tell yew that.

...If yew jes wanna compair the raw resistance with a nutter P/U this hook up will also suffice.

...If yew are looking for a reading tew giff yew a performance factor of sum sort this hook will dew yew noe good at all. Onlee general supposition and conjecture will prevail. For example sum say a 6K sounds worse than an 8K and knott takin into cornsideration the mag-a-nutes and winding style involved.




0le FUZZY

[tdowns]

Originally Posted by SinnerBoy61

Is this an acceptable way to measure a pickups output?

Back to the original question. You are asking if doing a resistance measurement is a way to measure a pickup's output. The answer in a word is NO. I'm not sure how resistance became the "standard" for measuring a pickup, but it really doesn't tell you much. It is a valid check to know the windings are continuous and that the pickup is not electrically open. If two pickups have the same parts, size, magnets, design, and wire gauge, a higher resistance will equate to a higher output. It will not be a valid "output test" across various manufacturers.

I have measured various pickup's using a test pickup. I injected the signal from a sine wave generator into test pickup, and held it over the top of the pickup under test so their fields would interact. I made some plastic standoffs to space the pickup a repeatable height off the other pickup. I just measured the output of the pickup under test with an oscilloscope. I could have alternately used an AC voltmeter. I used 500Hz as the test frequency since it is unlikely that the resonance of any pickup/pot/cable combination would be anywhere close to a frequency that low. I didn't want to go too low as to get in the region where the magnetics poop out. Using a higher frequency would be in the resonance region and no two guitars would have exactly the same electrical resonant frequency. This would result in measurement error every time.

I had a friend claim his guitar output was low. After checking a few things (including resistance and string height), told him it was OK. It played plenty loud into my test amp. I did the test I described above and found his pickups were ~20% higher than any pickup I had in my collection. I think he's going deaf.

[tdowns]

Originally Posted by jwells393

Measure the output of the switch with respect to ground (the ungrounded outside tab on the volume pot. The reading you get will be a little less than the actual resistance of the pickup. The pickup and the volume pot are in parallel. The equivalent resistance is determined as follows:

Attachment 2239

As an example assuming the actual resistance of your pickup was 6 K ohms and the pots are 250K............ (6x250)/256=5.86 K ohms

Right jwells!!

TO make it a little easier, I'll rearrange the equation to solve for the pickup resistance knowing the pot value and the total reading.


Rpu = 1/(1/Rt - 1/Rvol)

Where:
Rpu = pickup resistance
Rt = Total resistance (your measurement at the output jack)
Rvol = volume pot resistance

Remember the pot will not be exactly 250.00000K or 500.000K. They vary a lot.

Also, capacitors are open circuits to an ohmmeter, so tone circuits will not affect the measurement.

I'm not sure if anyone mentioned it, but you will need to turn the volume control all the way CW for this to work too (except Fuzzy's way). Fuzzy's way is the most straightforward, unless you don't want to take the control plate out. Then you can resort to the calculated method.

[0le FUZZY]

but I was wondering if I could take readings from the inside of the tele's control cavity

...I ant-sired in the affirmative and gave a method er sew I thought HEE! HEE!


0le FUZZY