Hum only when the middle pickup is active...

[Lumberjack]

I've put together a new HSS guitar with a DiMarzio 36th anniversary PAF and two Area 67 pickups. This wiring scheme was used:

http://www.dimarzio.com/sites/default/files/diagrams/1h2virtualv5w1v1ppt_split_bridge.pdf

It's a fairly simple circuit. Volume and a tone pot that only splits the PAF Humbucker.

I've wired everything accordingly and everything seems to be fine except the middle position. Once the middle pickup is selected (position 3), I have to touch a pot or the strings to silence the hum. Before mounting the wired pick guard, I checked each connection with a multimeter and I didn't notice any ground loops.

Also, the split function makes the humbucker really noisy... I'm not sure if that's the way it's supposed to be? I can still hear some hum even if the full humbucker is operating. At least the neck single coil seems to be hum-free...

Any suggestions on which connections I'd need to check?

 

[Logrinn]

Is the bare wire of the middle pickup connected to ground?

And, yes, when you split the humbucker, you disconnect the other coil and you lose the humbucking effect. A solution would be to instead have the humbucker be in series normally, and when you pull the switch have it parallel. The parallel sound is a "single coilish" sound, but you still have it in humbucking mode = ie quiet.

 

[Lumberjack]

Yes, all the bare wires are connected to the volume pot chassis. I also connected the tone pot, the claw ground cable and the jack ground cable to the volume pot. I checked the connections with a multimeter:

Jack ground - Volume pot -> Beep

Jack ground - Tone pot -> Beep

Jack ground - Claw -> Beep

Volume Pot - Tone pot -> Beep

Don't know what else there is to check... have I missed something?

 

[Logrinn]

And the neck pickup doesn't show this behaviour, ie that there's hum when you don't touch the strings or the bridge?

 

[Lumberjack]

I guess I haven't heard it before, because the neck pickup has a lot less highs than the mid or bridge pickups, but now I was able to hear a bit of a difference once I touch the strings, bridge or the pots... so I guess all pickups may have this problem. I just don't know what else there is to check...

 

[Cagey]

When you split the bridge pickup, it becomes a single coil, which is always noisy. Also, while combining it with any other pickup you'll still hear noise. There's not a whole lot you can do about it; it's the nature of the beast. No amount of shielding will help it, either. Your best bet is to buy into a noise gate. If the noise is not horrendous, you'll be able to set the threshold on the gate low enough that you probably won't even notice it operating.

 

[stratamania]

The middle pickup is an Area 67, which is a noiseless pickup with four conductors. It might be worth checking that the black and white wire are soldered together and fully insulated.

 

[Lumberjack]

I was thinking that it might be the type of wire that's responsible for the hum? I used clothed wire for all the ground connections... maybe I should've used shielded wire? Especially on the cable that goes to the output jack?

And what about bad solder joints? But if there were any bad ones, the multimeter wouldn't beep, correct?

 

[Cagey]

Cloth insulated wire is just something that some like to use for "vintage" appearance. It has no special electrical characteristics. Back when Leo first started building electric guitars, plastic or rubber insulated wire was somewhere between rare and non-existent, and certainly expensive. That it's still used at all today is testament to how hidebound guitar players/builders can be. Modern thermoplastic insulated wire is cheaper and easier to use.

In any event, you don't shield ground wires. You ground the shield on shielded cables. Shielded cable is a must for noiseless pickups, usually a must for output jacks. It's surprising what a few inches of unshielded wire can pick up. For single coil pickups, it doesn't matter.

"Beeps" aren't necessarily true indications of continuity. A less-than-ideal connection may still report as intact. But, it's unlikely that's your problem anyway.