Measuring installed pickups

[Bizman62]

I'm having doubts that I've installed the pickups wrong on my latest build, the semi hollow neck thru. The neck is loud and the bridge is weak no matter how I adjust the height. The pickups were marked N and B but there's no way to check the bottoms without an endoscope which I don't have. Normally I'd just unscrew the pickups but in this case the assembly was so tricky I'm not tempted to do that.

I've understood that the bridge pickup usually is hotter to better catch the weaker signal at the end of the string. So is there a way to measure it through the jack? If there is, what should I measure? My multimeter knows volts, amperes and ohms.

[curtisa]

Set multimeter to ohms, plug a lead into the output socket and connect your probes to the tip and sleeve of the lead. Wind all volumes/tones to max and use your pickup selector switch to isolate each pickup. The measured ohms on the meter should show the difference between the two pickups assuming they're wound to different specs.

[Bizman62]

So ohms is the ones to measure.

Does higher ohmage mean hotter? The neck says 6.2k and the bridge 6.8k

[curtisa]

Generally, yes. Aasuming the same size wire is used on the two pickups, higher ohms indicates that more turns of wire is on the bobbin, which corresponds to more output.

[Bizman62]

Thanks! Now that it's confirmed that the pickups are in the right positions the only thing I can do is to remove the springs from the bridge pickup to get it a tad closer to the strings. The springs are conical so the effect isn't much more than the thickness of the steel wire but it'd be to the right direction.

[mistermikev]

haha, I've been in this position so many times (installed but something clearly wrong and don't want to mess up my pretty wiring to rewire!)

honestly those pickups are so closely matched... but then freq vintage pickups are close like that.  I'm going to wager an issue with magnetic polarity.  seen it a thousand times.  if these are humbuckers... I'd start to consider that perhaps you got a weak magnet.  You could probably swap the two magnets without fully taking them out... err... maybe. 

if it was magnet... you could pass it through a couple of rare earth mags and restore the magnetism. 

if this is single coils... I'd start to wonder about one or two poles being flipped.  this has happened to me and it's a bear to track down.  it ends up sounding sort of 'out of phase'.  bass is all cancelled.  you can test this with a camping compass - passing it over the top to check magnetism you'll see it flip over on certain slugs.

hope some of that helps.

 

[Bizman62]

Thanks for the ideas @mistermikev. They're humbucker sized P90's made in China, cheap as soap. Taking them out is a no-brainer - unscrew, push one end in and pull the other end out. Putting them in with the springs took a day.

There seems to be no 'out of phase' thing going on, the bridge has just much a noticeably weaker volume. I could lower the neck pickup by a couple of mm's, almost level with the body, but doing that would get some of the bite of it off. At the moment the clearance to the strings is about 7 mm at the neck and 5 mm at the bridge.

[mistermikev]

13 minutes ago, Bizman62 said:

Thanks for the ideas @mistermikev. They're humbucker sized P90's made in China, cheap as soap. Taking them out is a no-brainer - unscrew, push one end in and pull the other end out. Putting them in with the springs took a day.

There seems to be no 'out of phase' thing going on, the bridge has just much a noticeably weaker volume. I could lower the neck pickup by a couple of mm's, almost level with the body, but doing that would get some of the bite of it off. At the moment the clearance to the strings is about 7 mm at the neck and 5 mm at the bridge.

6.8k is decent output... but admittedly if it is too close to the bridge the output will be drastically reduced.  lot of things you could try... changing the magnet for dif freq response, brass plate on the bottom(dif freq response), bigger strings, but there really isn't anything that's going to add output other than a boost circuit.  at the end of the day... replace the bridge with higher output pickup would be the best.

my dano style has a version of this issue going on in the bridge pickup.  those pickups are all 4k so really low output to begin with. the one closest to the bridge is noticeably quieter.  I have oft thought of buying a replacement... but you want to talk about hard to mount... it has dano style bent brass inside that similarly took hours to get in there without bending it such that the pickup wouldn't come back 'up'.  further, it's not quite bad enough that it even sounds bad... so motivation is low!

afa springs... I use silicon tube because (esp on p90 or other surface mount) springs are just a pain in the arse and can make noises that ruin a recording. 

[Bizman62]

48 minutes ago, mistermikev said:

if it is too close to the bridge the output will be drastically reduced

Hmm... The bridge pickup is about 1 cm closer to the actual bridge pieces than on the El Pish which has similar type of unbranded pickups from another Chinese vendor. That's in the ballpark of 45 mm v.s. 55 mm. The clearance to the strings is much less, only a few mm's. The bridge on the problematic one is a wraparound which makes it double as massive as the Tune-o-matic on the other one and there's enough of ferrous metals for a magnet to stick. Then again, the same magnet sticks to the T-o-m as well, a plenty powerful neodymium one salvaged from a hard disk drive.

If it was about a Strat type single coil with magnets on the bottom side swapping them would be easy. These are inside a humbucker cover with a bottom plate soldered to the sides. I'm hesitant to desolder for just getting a look inside.

[mistermikev]

well... I suspect it is a magnet that is weak just on gut.  can you test how magnetic one is vs the other (just with a low power magnet).  you can stick a magnet to the top/side and see if it improves. 

[Bizman62]

11 hours ago, mistermikev said:

you can stick a magnet to the top

Never thought of that! Clever!

Then again, as has been discussed elsewhere, it makes a whole lot of difference if the polepieces are magnets or just iron magnetized from the bottom. A magnet on top would be similar to the magnetic polepieces so it would be comparing apples to oranges.

But I can try to make a mock up magnetic measuring tool of a feeler gauge and a block to see if the pole screws suck a plate of steel from the same distance. Thanks for freeing my mind!

[ScottR]

21 hours ago, Bizman62 said:

the bridge has just much a noticeably weaker volume.

I had that once with a set of P-90s. The magnets were reversed. I sent them back and the builder re-oriented them properly and they came back noticeably louder.

SR

[mistermikev]

7 hours ago, Bizman62 said:

Never thought of that! Clever!

Then again, as has been discussed elsewhere, it makes a whole lot of difference if the polepieces are magnets or just iron magnetized from the bottom. A magnet on top would be similar to the magnetic polepieces so it would be comparing apples to oranges.

But I can try to make a mock up magnetic measuring tool of a feeler gauge and a block to see if the pole screws suck a plate of steel from the same distance. Thanks for freeing my mind!

well for the record I just meant temporarily.  if you find it solves the problem you'd want to take it out and run it through some rare earth magnets to restore magnetism. 

"free you mind... and the rest will follow" hehe...

also, I have some big magnets that I have used to change magnetism on single coils... man those things can pinch.  I used to keep a number of them around but one time they were separated and got attracted and it actually connected so hard it chipped one of them and shrapnel went flying.  can be seriously dangerous!  I've since been very careful when having them out and making sure to return them all safely!