Single coil hum

[MrGlyn]

Hi Guys,

 hope everyone is doing great.

 I've got what I think is an odd problem. I've just screened a Strat for the usual hum problem. I've done lots of these and I've always been happy with the result. But this one has developed a hum when I touch the pole pieces.

 This is a new Strat, I don't think this particular low hum was there before.

 Anyone got any thoughts on what's happening here? I'm thoroughly perplexed.

 Cheers

   Glyn

[Len Biglin]

Hi Glyn , Id say the windings have shorted to the pole(s) . This seems to happen on one pickup but not another , I dont worry

just avoid touching it.You can try measuring resistance from end of guitar lead to pole (there is often some laquer on poles) while vol is on 10. I'd expect no connection at all , but you may have zero to 6K ohm if it's humming .Len

[Pierre-Antoine Roiron]

You can try to solder the poles to the ground, or lacquer the poles. Your body can drive some electromagnetic field into the poles when touching them : grounding or insulating helps avoiding it.

[Gary Fried]

Yeah this means that somehow the pole pieces are injecting noise into the coil. You can ground the pole pieces by using some copper foil tape. As a matter of fact carey nordstrand uses this method on his pickups. I have done this many times and it works but you must remember to thoroughly scrape the bottom of the pole pieces to make sure that you get a solid connection to the tape. Check the pic to get a better idea of how to accomplish this. 

[Pierre-Antoine Roiron]

This work only if you use copper tape with conductive glue. Fortunately, every copper tape I've used for now has conductive glue.

[MrGlyn]

I'm not so keen on the conductive adhesive myself. I don't trust it. I always put a wee bit of solder to join each piece. Helps prevent it peeling away on the corners too.

Having said that, I've never had a problem with the conductive glue - it's just what works in my mind.

We all have our different ideas about things.

Thanks for the reply

 Glyn

[MrGlyn]

Hi Gary, thanks for the info.

Earthing the bottom of the poles worked. I wonder how that works?

So good to have access to experienced minds - Cheers Mate :-)

[Pierre-Antoine Roiron]

Grounding pole pieces make it impossible for your body touching them to inject some electromagnetic field (your body is some kind of antenna), because electromagnetic fields cannot travel in fixed-potential conductive materials.

AT least that's what I understand of it.

[Gary Fried]

Pierre that's a good point. I too always buy tape with conductive adhesive. 

[Len Biglin]

I would not recommend soldering poles as heat effects magnets .

[MrGlyn]

Hi Len,

 in what way does it change them?

[Joshua Levin-Epstein]

Ferromagnetism is the result of individual magnetic domains in (potentially) magnetic material being aligned. That's why you can rub a magnet against a nail and turn the nail into a magnet. Heat will cause the domains to vibrate and misalign. Another way to misalign the domains is shock, so don't drop the pick-up...

 

By the way, magnets that have weakened for whatever reason can be "re-gaussed". 

So much for my knowledge of 6th grade science. It's been a while...

 

Joshua

[MrGlyn]

Hi Joshua,

 you remember a lot more of school than I do.

Do you have any idea what the resulting sound would be for a pickup? Just to save me experimenting and stuffing one up :-)

Is it possible to do it by getting the soldering iron too close when soldering the contacts I wonder.

   Glyn