Pickup question

victorludorum

I've just bought a split-coil single that I asked to be reverse wound, so that it would cancel the hum when run on its own. I wanted to check that it had been done by putting the two coils together, which should result in them sticking together I believe. I tried this, but they are neither attracting nor repelling. I tested the poles with a mangetised screwdriver and I'm getting a result where one of the coils is equally magnetised on both ends of the pole pieces, while the other has a stronger pull (than the other coil) on the top of the poles, but nothing on the bottom. Is this normal?

Funkfingers

Is one of your pickups a stacked-coils noise-cancelling type?

In designs such as the DiMarzio HS series and Seymour Duncan YJM Fury, the rod magnets are not as tall as the bobbin form(s). Thus, the exposed end of each polepiece will attract ferrous metal whereas the underside end will not to the same extent.

Your test only really confirms opposite magnetic polarity. The coil winding direction also needs to be reversed to achieve noise-cancellation. 

OilCityPickups

Getting getting magnetism at one end and no magnetism at the other end of a magnet slug isn't physically possible. You can't have a magnetic 'monopole'. 

What brand and design is the pickup?

victorludorum

It's a true split-coil with 3 poles on each, like an XII pickup.

victorludorum

OilCityPickups said:

Getting getting magnetism at one end and no magnetism at the other end of a magnet slug isn't physically possible. You can't have a magnetic 'monopole'. 

What brand and design is the pickup?

This is what I thought. It's an independent guy who's made it. Should the pull be even, or is it possible to have one end which has a greater pull than the other?

Funkfingers

To clarify, are the polepieces of your pickup in the form of rod magnet sections à la original Fender or magnetisable metal slugs in proximity to a bar magnet?

The nearest that I can get to replicating your different magnetic field strength at each end phenomenon is with a semi-functional DiMarzio HS-2 replacement pickup for Stratocaster. This design includes a grounded metal sheet around three surfaces of the upper coil. The only possible uses of this are screening against RF interference and, arguably, deflecting the magnetic field from around the rod magnet polepieces towards the strings.

The metal sheet reduces the magnetic attraction sensed at the bottom of the DiMarzio pickup.

victorludorum

They are rod magnets. 3 in each pickup

OilCityPickups

When you charge a magnet it charges the magnet as a whole so what you put in one end shows up at the other ... unless something blocks it like a base plate or as @Funkfingers says ... there is a gap at the other side that spaces the magnet away from attracting a ferrous object.

Without being able to use a polarity tester and Gauss meter on the pickup, or really having any idea of it's internal structure ... even a pickup manufacturer like myself is whistling in the dark. 

victorludorum

As I said, I don't have a compass and I am simply using a magnetised screwdriver, but I'm getting almost zero pull from one end of the pole, but good pull from the other. I can't see in the middle obviously, but this result leads me to think that something isn't right.

Kittyfrisk

Might seem a radical suggestion, but have you tried the pickup in a guitar rather than waving bits of metal near to it?
You could use connector blocks rather than make a solder joint, so no permanent damage will occur in case it is faulty & you need to send it back.
If @OilCityPickups can't make a diagnosis without the proper tools, you (or I) don't have much chance 

Funkfingers

The problem is not tools but incomplete information.

Photographs or cross-sectional drawings of the internal structure of the pickup would help greatly.

victorludorum

Kittyfrisk said:

Might seem a radical suggestion, but have you tried the pickup in a guitar rather than waving bits of metal near to it?
You could use connector blocks rather than make a solder joint, so no permanent damage will occur in case it is faulty & you need to send it back.
If @OilCityPickups can't make a diagnosis without the proper tools, you (or I) don't have much chance 

It's a valid point that you make, and the answer is no, not yet. I haven't routed the guitar yet as it will need a special rout for this type of pickup, and I'm not keen on doing that unless I know that an XII pickup is going to work. This is the only guy I've seen selling them in the UK, so if his product isn't up to snuff, I'm a bit stuffed as it will mean buying a set from Novak and paying through the nose. I'll have to test them through one of my other guitars which has a humbucker rout, but that means removing the current pickup, which I'm a bit loath to do.

The fact is is that he's wound it too light anyway, as I asked for something in the region of 6.5k, but it's just a tiny bit over 5. In view of this and the magnet issue, I think I'll just return it.

victorludorum

Funkfingers said:

The problem is not tools but incomplete information.

Photographs or cross-sectional drawings of the internal structure of the pickup would help greatly.

It's a Fender XII pickup, which is basically like a split Strat pickup with 2 separate sections containing 3 poles each.

Funkfingers

Yes. I gathered that much. There must be something about your bespoke pickup that deviates from Fender convention. 

With respect, on its own, a d.c. resistance meter reading means very little. 

Filter’Tron pickups yield low meter readings but powerful magnets contribute to an overall recipe that works very well.

victorludorum

I don't think there's anything bespoke about them; they're just a copy of XII pickups. Wire wound around rod magnets is all I can see.

I've sent the guy a couple of questions, so I'll see what he comes back with. Cheers all ;-)

p90fool

You can actually test pickups by putting them above the string rather than underneath.

If you have a twin pickup guitar with the reasonable gap between the pickups you can rig up some blocks of wood/Lego/whatever with some tape and suspend the pickup face down about 5mm or so above the strings, where you would naturally fit a middle pickup. 

Wire it or tape it to a guitar lead and see what happens. I do this all the time when I want to know whether a pickup is functional before I fit it. Obviously it'll sound like a middle pickup rather than whatever position you intend to fit it in, but it'll let you know whether it works and a good idea of how powerful it is when you compare it to others on the same amp settings. 

Funkfingers

p90fool said:

You can actually test pickups by putting them above the string rather than underneath.

Wire it or tape it to a guitar lead and see what happens. I do this all the time when I want to know whether a pickup is functional before I fit it.

I do something similar when I wish to roughly evaluate the tonal properties of a pickup. This is crude but it can save a lot of string changing and soldering work. 

Most recently, I discovered that a replacement pickup for Stratocaster neck/rhythm position was better suited for the centre position of my Eighties Charvel project.

thegummy

p90fool said:

You can actually test pickups by putting them above the string rather than underneath.

If you have a twin pickup guitar with the reasonable gap between the pickups you can rig up some blocks of wood/Lego/whatever with some tape and suspend the pickup face down about 5mm or so above the strings, where you would naturally fit a middle pickup. 

Wire it or tape it to a guitar lead and see what happens. I do this all the time when I want to know whether a pickup is functional before I fit it. Obviously it'll sound like a middle pickup rather than whatever position you intend to fit it in, but it'll let you know whether it works and a good idea of how powerful it is when you compare it to others on the same amp settings. 

That's great advice.

I wouldn't have assumed a pickup could go straight to the lead like that but now you mention it, it's so obvious that it would.

Winny_Pooh

5k instead of 6.5k would be a no from me

victorludorum

Indeed. He's trying to tell me it may be my meter, which is not the case as it gives me correct readings for all my other pickups. He says he'll send me another one if it's not what I want, but my confidence in his product has dropped to almost zero. I'll wire them in and see what happens...

p90fool

Winny_Pooh said:

5k instead of 6.5k would be a no from me

Doesn't it depend on the construction of the pickup?

If you measured the DC resistance of a PAF and then a Filtertron you might well think the Filtertron was broken.