help with killing hum on Dean Markley Pro Mag p/u

[guitarbolt]

Hi folks.

Just stumbled upon this site and while I hope that I'm not adding yet another thread to the redundancy pile, I'm also not so keen on reading the gargantuan FAQ to gain mastery on the physics of a pickup. (I kind of turned away once I saw it divided into hyperlinked chapters!) That said, I am heir to an old Dean Markley Pro Mag pickup and when plugging it into my Novation X-Station, I find it giving a really irritating hum. My suspicion is something related to grounding and shielding from the very little I know of either of the two. I just know that the hum turns into a really loud buzz when I start fiddling around with the area where the 1/4" plug and the cable meets.

At any rate, is this something that can be solved with a few sheets of aluminum foil or will it involve something more complicated? Thanks.

[pete12345]

Pickup basics 101: coil of wire wrapped round one or more magnets. Steel string moves within magnetic field, generating a small voltage across the ends of the wire. This alternates depending on which direction the string is moving, so you get an electrical signal that matches the frequency/amplitude of the string.

RW/RP: Stands for reverse wound, reverse phase. The pickup wire is wound in reverse (or just wired so the connections are reversed), which puts the noise and signal out-of-phase The magnets are also turned over, so the opposite pole is on top. This puts the signal back in phase, but does not affect the noise.

If combined with a normal pickup, this means the noise signals cancel, but the desired signals add, reducing the amount of noise. Almost any 2 or 3 pickup guitar or any guitar with a humbucker will contain a RW/RP pickup.

I find it giving a really irritating hum.

Generally implies poor grounding and/or poor/nonexistant shielding. Rewiring and shielding would almost certainly help.

the hum turns into a really loud buzz when I start fiddling around with the area where the 1/4" plug and the cable meets.

Could imply a bad cable. If the plug is the rewirable type, check the soldered connections. If they're ok, cut the broken section out and reattach the plug (if it's a moulded plug or you don't want to rewire, get a new cable)

[guitarbolt]

I guess then the next question would be, how does one go about rewiring or reshielding this particular acoustic guitar pickup?

Below is a photo of the plug disconnected from the cable of the pickup, which was only locked with a screw. that's to say, the plug doesn't haven't a threaded "shell" like normal guitar 1/4" cables but as you can see from the hole in the plug, a tightened screw holds the cable to the plug. Unfortunately, upon unscrewing the plug, I found that my attempts at putting it back together are in vain. That's to say the pickup doesn't seem to work anymore.

I'm just shocked that the amount of contact between the cable and plug hinges upon the narrow strip of copper wiring. Now that my pickup's "done for" I figure now's a good time to modify it and correct the initial design flaws of this thing. Thanks.

[guitarbolt]

so...

gathering from the lack of responses, I'm going to say that this the topic I chose isn't for this particular forum. If this is the case, I'd appreciate any leads on which forums to visit for information on how to mod -- and with my recent tinkering, repair -- my dean markley acoustic pickup.

[JohnH]

This is THE place (IMO), but then theres the 'other' place, which is the Project Guitar Forum, which has lots of smart people, but not as smart as us, except for those of us who are on both!!

Your pickup, clearly the plug is off and won't go back on. Do you have a multimeter? if so, you can measure the resistance between the centre and the outer braid. Most pickups would be in the range say 5k up to 15k, and there should be very low resistance from the outer braid to the case of the pickup. If those work out, then the wiring is probably fine and grounding ok.

In which case, its probably just a matter of stripping back the wire and soldering on a new jack plug.

John