Hum With Sd, Alnico Ii Pro Humbuckers

[kench]

Hello.. I installed two Seymour Duncan Alnico II Pro humbuckers to the LP I've built. I ground shielded the control cavity and the toggle switch cavity (not yet the pickup cavities) but it still gives me "hum" that is not common with humbucker pickups. It's not noisy as a single-coil but still annoying when playing with high gain. I checked my wiring many times.. but I couldn't find anything wrong.

1) Are all Alnico II Pro pickups noisy? (Their output is much less than most humbuckers btw)

2) Over-heated pots or capacitors may cause hum? (I might have done that before I found out the pots were lacquered so I couldn't solder)

3) Isn't a pot's shaft is connected to the pot's back? (I didn't connect the back of the pot's to the shielding as I thought it is already touching the shielding on the shaft area)

5) Shielding the pickup cavities may help? (Planning to do it when I remove the strings for fret leveling)

4) Any other possibilities may cause hum?

[kench]

Btw.. I forgot to add. The hum is less when using both pickups and more when switched an individual pickup. (like with a single coil). And I wired them like in the diagram came with pickups.

And the electronics I used are:

-Two SD Alnico II pro humbuckers (neck and bridge)

-Four CBS brand 500 K pots that came from Warmoth (they are a bit different from the others I've seen.. but they look very good quality)

-Two .047mf film capacitors.

[1guitarslinger]

The SD Alnico 2 Pro pickups should not make any more noise than any other vintage style humbucker.

Sounds like the problem is not the pickups, but the wiring and shielding.

First off, if your shielding is not grounded properly, and that means every bit of it, it will actually generate more noise, as it acts like a noise antenna. ANY ungrounded metal will act as a noise antenna. If cavity shielding is not done so that all of it has perfect continuity to ground, it will cause more harm than good.

Check to make certain that the ground from your output jack is running to all of your pots, and to your bridge or tailpiece. Also, the housing (frame) of the selector switch must be grounded as well. This is usually done by soldering the wire shields to it's housing that are grounded on the other ends to the pots.

Depending on how well your shielding was done, properly grounded pots and selector switch should provide the ground to it because of the physical contact.

The pickup cavities really don't need to be shielded on a humbucker guitar, and really the other cavities typically don't need it either if wired properly with shielded wire.

Any time somone brings a guitar like this to me with noise problems, I rip out all of the home made cavity shielding, wire it properly, and give it back to them. So far with 100% satisfaction.

Edit: Make certain the pickups are wired properly for series, humbucking mode.

Duncan diagram link Disregard the coil split mini switch. Green and Bare are soldered to ground. Red and White soldered together, then insulated with tape or heat shrink. And Black is the signal hot.

[Wymore Guitars]

First off, if your shielding is not grounded properly, and that means every bit of it, it will actually generate more noise, as it acts like a noise antenna. ANY ungrounded metal will act as a noise antenna. If cavity shielding is not done so that all of it has perfect continuity to ground, it will cause more harm than good.

Use an ohmeter and check all your shielding back to the ground lug of the input jack to make sure there is continuity. You should see less than 5 ohms in all cases.

Also make sure you have the pickup coils wired correctly as posted above and that the bridge and three way switch are properly grounded.

[1guitarslinger]

Use an ohmeter and check all your shielding back to the ground lug of the input jack to make sure there is continuity. You should see less than 5 ohms in all cases.

Also make sure you have the pickup coils wired correctly as posted above and that the bridge and three way switch are properly grounded.

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echo...

[kench]

Use an ohmeter and check all your shielding back to the ground lug of the input jack to make sure there is continuity. You should see less than 5 ohms in all cases.

Also make sure you have the pickup coils wired correctly as posted above and that the bridge and three way switch are properly grounded.

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I just tested all ground points with an ohmeter. Kept one tip at the output jack's sleeve.. and touched all ground points, including shieldings and the bridge with the other tip. Everything good, value is close to what I got when I touched one tip on other. Except... ohmeter showed electrical contact between the toggle switch's middle terminal (which is supposed to be the hot output from the guitar) with the ground. I cannot tell you the value because the ohmeter was not calibrated (reset) but it was a bit weaker than ground to ground contacts but I don't think I should be getting any electrical contact there. But then again, if hot output and ground is in electrical contact, I shouldn't be getting a decent sound from the guitar, right? The guitar doesn't sound so bad. Just noisy. I'm a bit confused now.

And for the polarities of the pickups. I thought of that. But if the pickups are in phase with each other, shouldn't it be noisy when both pickups are active? Or am I wrong? This is the first guitar I've built and the first humbucker guitar I've owned. I get hum when I use individual pickups, not when I use both pickups.

[1guitarslinger]

It sounds like something is wired incorrectly.

You will read some resistance between your signal hot and ground, but it should be in the K ohms, unless your volume control(s) were rolled off when you took your reading. If the volume controls are set to zero, you will read ground at the signal hot.

If your volume controls were set at 10, then depending on the selector switch you are using, you may have confused the switch housing ground, with the middle terminal, or have some other wiring problem(s).

Polarity of the pickups is not the only concern with the pickups' wiring. There are many ways to wire a 4 wire pickup incorrectly.

Make certain that your pickup wiring conforms to this: DIAGRAM (disregard the coil split mini switch) Green and Bare are soldered to ground. Red and White soldered together, then insulated with tape or heat shrink. And Black is the signal hot.

If wired correctly, humbucking pickups should be quite noise free regardless of whether one or more is on at the same time.

Edit: From what you have described, it sounds like you may have both pickups wire as single coils. Make certain that the Red and White wire junction is insulated, and not soldered to anything.

[kench]

Make certain that your pickup wiring conforms to this:  DIAGRAM (disregard the coil split mini switch) Green and Bare are soldered to ground. Red and White soldered together, then insulated with tape or heat shrink. And Black is the signal hot.

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That diagram is the same with the diagram came with pickups... I wired my guitar that way. Unless I made a mistake when wiring.. or used a damaged wire, it should be ok. But it looks all ok from what i see now.

Here are the values I read on ohmeter:

-6 Ohms when touched one tip on another (ohmeter was not calibrated so this may be the reference value of a good electrical contact)

-6 to 7 Ohms between all ground points

And between the middle terminal of the 3-way switch and the jack's ground:

-11 ohms when the switch is in middle position

-17 ohms when the switch is on bridge or neck pickup

All values read when all volume and tone knobs are turned up to 10

It's a standard 3-way LP switch.. so I know which is the middle terminal and which is the ground terminal. I get 6 ohms with the ground terminal

(btw... the pickup's back plate is also a ground point, right? because I read 6 ohms when i touched the tip on the pickup's height adjustment screw.)

Thank you so much for helping me. But I think there's a mistake in my wiring that I couldn't see now. Soon I will have to remove the strings and hardware anyway for fret leveling and buffing the finish... I will re-wire the guitar and I hope it will be ok. Thanks again.

[1guitarslinger]

Can you post some photos of your wiring?