G'day to all 1st post and some wiring questions with multimenter

[PeterD]

Hi, sorry if this is long winded but as it's my 1st post I thought I'd get as much info into it as possible, all and any help highlty appreciated.
This in in relation to a non PTB guitar pickup upgrade I hope. I already had a couple of guitars before
i found this site and am looking to do some stuff to make them my own personal bit of kit. I'm thinking if I get these sorted I will look at getting the ES-1GL to keep the brain occupied.
I am left handed and a hopeless mid 60's learner who is not going to give up.

So instruments are a Yamaha Pacifica 112J and SX Tele
So far following info on this site I have reduced the girth and thickness of the SX neck and finished it with 4 coats of true oil and put in a bone nut. I'm pretty happy with how the neck turned and will probably look at pickups down the track but I don't think they sound bad, that's all down to my fingers.

So job in hand for the Pacifica (which is their only LH model) is a set of cheap FLEOR A5 pickups with coil split instead of stock Korean G&B ceramic and HB with no split
The pots and switch are alpha mini and I will leave them in. I am going with a mini off on off switch as per a youtube from guns and guitars which gives Nth single/ HB/ Sth single.

The main questions I have to start is testing hot wire with my multimeter on the original pickups (this is the 1st time I've opened the guitar up and looked inside) all 3 pickups have a single conduit with one white and a bare wire. So I assume white is hot (all white wires were going to the switch and all bare were joined and soldered to the back of the volume pot. My problem is I attach red from multimeter to white and blare bare wire then put a screw driver across the posts and I get a negative reading which goes positive when I pull away. Everything I've viewed I assumed it should go positive 1st. Red lead is plugged into VQmA and black into COM.
When I test the 4 wire FLEOR Humbucker with black on it's own, red & white joined together and green & bare joined together which looks to be same a Seymour Duncan on assumption. Test resistance and Black/White are one coil (Nth) & Red/ Green (Sth) so when I put the multimeter red lead on black wire and black lead on white wire I also get a negative reading. I would assume Black is hot especially as it was the only wire on its own.
So is this as it should be????

2nd question is on shielding I have done the pick guard and cavities and checked all over for continuity all seems good. Should I earth the cavity to say the spring claw or just leave as is with no earth attached?
Pete

[JimC]

I don't understand what you mean by negative reading. Its early in the morning here in my defence. I've failed to work out what your problem with the pickups is. I will note that until I got some practice in I found it surprisingly hard to get consistent measurements with a resistance meter on pickups. It was very easy to confuse the hell out of myself and I managed to conclude some good pickups were bad and all sorts of schoolboy stuff. It seemed much more important than I thought it ought to be to get the meter on the right range even when I only wanted conducts/doesn't conduct results.

In answer to your second question, yes, connect shielding to earth somewhere.

[Simon Barden]

Are you trying to work out the signal polarity of each pickup by using a multimeter for resistance reading and then seeing whether the value increases or decreases slightly if you bring something metal up close to the pickup?

It really doesn't matter if the pickup values all go up or all go down, as long as they go the same way. If two go up and one goes down, then that single pickup will produce a signal that is the opposite polarity to the other two, and when used in combination with another pickup, you'll get a very thin wiry sound.

The Fleor pickup appears to be wired in the Seymour Duncan convention. Again, the the output signal polarity only matters when you are using it in combination with another pickup. A pickup manufacturer will normally be consistent in how they wire up and arrange the magnets in their pickups so that they all have the same relative polarity, but between different manufacturers, you'll find that some use one polarity and some the other. That's when it's important to check the polarity of the pickups.

If you have single coil with two separate output wires, then you can simply swap the connections over to change the polarity of the output signal if necessary. With a humbucker, if you have a 4-wire connection, then again you can swap over the hot and ground wires to reverse the signal polarity, but you will have to disconnect the screen from the original ground wire and connect it to the original hot wire.

What is a problem is if you have pickups, either single coils or humbuckers, with single wire + screen connections and the pickups have different polarities. You can't simply swap the connections over and use the screen as the hot connection, as the screen will then carry the hot signal and pick up a lot of electrical noise as it's no longer screened. You've then either got to partly disassemble a pickup so that you can do some very fiddly rewiring to swap the hot connection and screen connection over, or change the pickups so you have a set with the same polarity. You can opt to just live with the very thin nasal sound of mixed polarity pickups when using two (or more) together, and it can be a useful sound occasionally, but I do find that I prefer the standard sound a lot more.

Things become even more complicated when looking at Telecaster pickups (or related styles), as the Telecaster bridge pickup has a grounded copper plate underneath it, which will be connected to the bridge plate through the mounting springs. So even if you have a Tele bridge pickup with two separate output wires, you can't simply swap them over, as the hot output will be grounded through the mounting springs to the bridge plate and you get silence. So you then have to swap the bridge plate ground connection over. The Tele neck pickup also has issues here, as the metal cover is connected to the normal ground wire, so again, even if the pickup has two separate output wires, you'll need to swap that cover's ground link over (or disconnect it entirely as some people do).

And as Jim says, yes, the screening all needs to be connected to ground. This is normally done via the pots which will be grounded. they then touch the shielding on the underside of the control plate itself (or the metal control plate on guitars like a Tele), so grounding those items. You run the shielding tape up over the edge of the control and pickup cavities so that they touch the tape on the pickguard or the metal control plate so they become grounded. If you can. run the tape up to or close to one or more screw locations so there is positive pressure holding the bits of tape together. Pickguards can sometimes lift in the middle, so connectivity isn't always guaranteed unless the connection points are by the screws.

The shielding should form a complete as possible enclosure around the pickups and control components. Any gaps should be as small as possible.

Any separate cavities with shielding will need a ground wire run between them and back to a ground connection which can be another shielded cavity that is definitely grounded. I normally just use a piece of wire and tape down the bare ends with more copper tape.

You don't need to shield the trem cavity itself.

[PeterD]

Tks Jim,
I guess I'mm looking at too much stuff on internet sites about all this.
Main thing was trying to understand my multimeter on this. I'm all good on continuity and pickup resistance.
The one that got me was setting the meter volts. On several sites I got the following info.

Once you have established which wires are pairs for each pickup
Connect one lead to one wire and the the other lead to the second wire of that pair, set the multimeter to 20DCV
Now slowly move a screwdriver or such towards the slugs if you get a positive number as it comes in contact and then goes negative as you pull away the "hot wire" is attached to the red lead of the multimeter.
If it gives a negative reading as you you the screwdriver in contact and it reads a positive number as it pulls away the hot wire would be on the black lead.
This is what was doing my head in as even the pickups that are originally in the guitar I know exactly which wires were connected to the switch and which were connected to the back of the pot as earth. These were all going negative (a minus sign) as I put the screwdriver in contact with the slugs and red lead from multimeter connected to the wire that was going to the switch and black (Comm) lead attached to the wire that was going to the back of the pot.

So I think it was information overload and I'm overthinking everything. I'll just connect it all up and see if it sounds okay, or even makes sound, then may just need some tweeking wire swapping.
Pete

[PeterD]

Tks Simon,
I'll try to absorb the detailed info you've given me.
I gave an explanation of my getting hung up on the hot wire in my reply to Simon, meant for both of you.
I appreciate the feedback from you guys and I'll let you's know how I think these cheap pickups sound compared to the ceramics that were in it.