can you test a pickup?

thumbzilla · #1 10-25-2006, 02:09 PM

Last night at rehearsal, we were having problems with buzzing thru the mixing board. In the process of troubleshooting that (my amp got the blame but was later vindicated), I noticed that the bridge pickup volume knob didn't seem to change anything. Is there an easy test or something before I take it to a shop? The instrument is a Squier P-bass special.

Scott in Dallas · #2 10-25-2006, 08:11 PM

If you turn the neck pickup volume almost all the way down, and the bridge volume doesn't change anything, isn't that your test?

thumbzilla · #3 10-25-2006, 08:48 PM

I guess I was hoping for an electronic verification that the pickup is the problem. In circuitry there are continuity and such tests which can isolate a component and see whether or not there is current flowing, etc. Maybe the knob is the fault, maybe there is a bad solder joint--I dunno. I don't even know where to look on a bass, never seen inside one. The website has a simple wiring diagram but no instructions on disassembly. There is a plate on the back, but when I took out two of the four screws, the neck started to get loose, so I stopped, figuring that was the base of the truss rod. Are the guts under the pick guard?

Scott in Dallas · #4 10-25-2006, 08:58 PM

Yes. You'd need to remove or at least loosen the strings and take out the screws holding the PICKGUARD to the body in order to access the electronics. From there you just need to follow the wires to see if something is loose. I'd bet you've got something loose in there which should be fairly easy to see. Just be careful and take your time.

superjesus · #5 10-25-2006, 09:30 PM

Something is seriously fishy about this thread...

you should NOT have to remove the neck AT ALL, EVER to gain access to the electronics cavity.

on your bass, access to the electonics wiring is achieved by removing the pickguard on top of the bass. you may have to slacken the strings or remove them, but you shouldnt have to take off the neck.

your problem to me sound more like a wiring problem (like a broken solder joint on a volume knob) than a pickup problem. pickups are fairly robust.

it might also be a problem with the electricity and the single coil picking up the 60 cycle hum.

open the pickguard up and look for any loose wires or connections and let us know what you find.

tadawson · #6 10-25-2006, 10:30 PM

Quote:

Originally Posted by thumbzilla

I guess I was hoping for an electronic verification that the pickup is the problem. In circuitry there are continuity and such tests which can isolate a component and see whether or not there is current flowing, etc. Maybe the knob is the fault, maybe there is a bad solder joint--I dunno. I don't even know where to look on a bass, never seen inside one. The website has a simple wiring diagram but no instructions on disassembly. There is a plate on the back, but when I took out two of the four screws, the neck started to get loose, so I stopped, figuring that was the base of the truss rod. Are the guts under the pick guard?

Under the pickguard is where you will find everything. Since a pickup is nothing more than a coil of wire on a magnetic bobbin, there really is nothing to fail, unless it has been violently mechanically attacked, which is unlikely. No moving or active parts inside, as they say. Pots, on the other had, ARE wearout parts, so I would start there, and also look for loose solder joints.

You say that the volume control does nothing, but do not mention if there is sound from the pickup fully up, or nothing (I'm guessing the latter, since you are suspecting the pickup . . . .). If that is the case, then I would suspect that the pot died, or the output lead came off of it, which would also give a potential source of hum.

Oh, and the easiest test for a pickup is to read it with an ohm meter - if you see zero, it's shorted, infinite, it's broken open, and pretty much anything around 100 ohms, it's OK.

- Tim

Scott in Dallas · #7 10-25-2006, 10:48 PM

Quote:

Originally Posted by thumbzilla

There is a plate on the back, but when I took out two of the four screws, the neck started to get loose, so I stopped, figuring that was the base of the truss rod.

Just to make help with the terminology, the plate on the back is where the neck bolts to the body, which is why it came loose as you loosened the screws. The truss rod is actually inside the neck and is only visible at the end where it has some device for adjusting the neck.

The "plate" I was referring to is the pickguard plate on the front of the bass. I'll go back and change the terminology just to make it more clear.

pkr2 · #8 10-26-2006, 07:34 AM

Quote:

Originally Posted by thumbzilla

I guess I was hoping for an electronic verification that the pickup is the problem. In circuitry there are continuity and such tests which can isolate a component and see whether or not there is current flowing, etc. Maybe the knob is the fault, maybe there is a bad solder joint--I dunno. I don't even know where to look on a bass, never seen inside one. The website has a simple wiring diagram but no instructions on disassembly. There is a plate on the back, but when I took out two of the four screws, the neck started to get loose, so I stopped, figuring that was the base of the truss rod. Are the guts under the pick guard?

I suggest that you stop right where you are. I really do mean this in the nicest way that I know to put it, but if you loosened the neck plate to get to the electronics, you need to let someone with more experience check out your problem.

I'm not sure what your bass is doing. You say that the volume knob changes nothing but that doesn't indicate what your bass is actually doing. The volume could be wide open, dead silent, stuck in one place etc.

If you are getting any useable output through the amp, the PUP is probably OK.

A little more info may narrow the possibilities down a little further.

Good luck.

thumbzilla · #9 10-26-2006, 05:08 PM

Relax.

The bass seems to be playing thru only the neck pickup. When I turn that volume control down, the bass goes silent. Messing with the bridge pickup volume knob does not make the bass play. I have seen other basses with an inspection plate on the back which accesses some electronics and a battery. I know that I do not have a battery, but I just started there. Wrong place, my bad. Thanks for your concern, though.

pkr2 · #10 10-26-2006, 06:10 PM

Quote:

Originally Posted by thumbzilla

Relax.

The bass seems to be playing thru only the neck pickup. When I turn that volume control down, the bass goes silent. Messing with the bridge pickup volume knob does not make the bass play. I have seen other basses with an inspection plate on the back which accesses some electronics and a battery. I know that I do not have a battery, but I just started there. Wrong place, my bad. Thanks for your concern, though.

It could be the pickup, and yes you can get a pretty accurate check with an ohm meter. It is more likely to be a loose connection, though.

Good luck

Scott in Dallas · #11 10-26-2006, 07:41 PM

I thought that with a dual volume control where they share a tone control that one volume is the "master" and when it's down all the way neither one works. If you turn that one almost all the way down and turn the one in question up and down do you hear a change?

tadawson · #12 10-26-2006, 11:33 PM

Quote:

Originally Posted by Scott in Dallas

I thought that with a dual volume control where they share a tone control that one volume is the "master" and when it's down all the way neither one works. If you turn that one almost all the way down and turn the one in question up and down do you hear a change?

Nah, I have a cheapo Fender P/J that is wired like this - each pickup has it's own volume, and they are totally independent of each other. They do share a common tone control. Most likely, this is nothing more than a bad pot, or a lead that came off or shorted on the one that does nothing.

Has the knob ever seemed "loose", such that the pot may have gotten turned inside the bass? That is an instant recipe for a broken or shorted connection . . . .

- Tim

vindy500 · #13 10-26-2006, 11:42 PM

yes take the pickguard off, thats the thing on the front of your bass. nelow the strings, check all wires are whole. if you cant see any wires with broken ends ect if you know how to solder try soldering the bridge pup straight to the jack. if no output from this time for new pickups. if you dont understand what im saying, take it to a tech

WarriorJoe7 · #14 10-27-2006, 01:11 AM

Warning: put your amp/pa system on low volume when doing this.

get a metal object such as a screwdriver or allen wrench that you can use to tap on a pole piece of a pickup. It can be any metal object as long as you can get it to tap the polepice and it has to be metal.

Turn both your volumes off. Now turn one up and tap on polepices of both pickups. It should be obvious which pickup is being used and which is not, by the clacking or lack thereof coming out of your amp. Now repeat with the other volume.

I do this alot when i can't figure out what kind of electronics setup a bass has. I use this to help distinguish between 2 seperate volumes or a volume and a pan. Workd like a charm every time.

Thanks,
joe

thumbzilla · #15 11-02-2006, 07:14 PM

It was a loose wire to the volume control knob. Had the store fix it--warranty. Sounds great now.