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Post by chupucabras on May 26, 2006 15:11:42 GMT -5
Hi,
A while ago I shielded and star-grounded my Epiphone SG400, which seemed to work okay, but lately I noticed that with the pickup switch in the middle one of the volume pots was affecting both pickups.
So I checked the original schematic for SG-type two humbucker wiring on the guitarnuts site against the innards of my guitar and realised that I'd wired it incorrectly before. I resoldered everything into the correct places and tried it out, and the middle pickup position seemed to work correctly, until I hooked up to my Marshall Bluesbreaker II distortion pedal...
With the distortion active, and the pickup switch not in the middle position (ie. just one pickup selected), turning the volume pot for that pickup all the way down does not kill the sound completely. However, if I turn the other pickup's volume all the way down it does kill all the sound.
So it seems like some of the signal from each pickup is leaking over into the other channel. This leak is only audible when the distortion is on, I'm guessing this is because of the gain involved in any distortion, but it did also occur to me that it might be some kind of weird impedance thing...
I've checked the wiring very closely and can't see any obvious shorts or bits of wire going where they're not supposed to.
Does anyone know what might be causing this behaviour?
Dan
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Post by UnklMickey on May 26, 2006 16:37:37 GMT -5
hi Chupucabras,
Welcome to Guitarnuts2.
when trying to figure out what might be causing this, the first thing that comes to mind would be a small amount of current in the ground would be audible with copius amounts of gain.
but that's exactly the sort of thing star grounding is supposed to eliminate!
maybe enough leakage through solder flux at the selector switch lugs?
even if the switch leaves don't separate very far, i doubt the capacitance would be enough to allow audible bleed-thru. but you never know.
if you disconnect one of the wires going from a pot to the selector switch, and still have the bleed-thru. that points to ground current.
if it goes away that points to a problem at the selector.
unk
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Post by sumgai on May 27, 2006 22:11:16 GMT -5
Dan,
Turning down the pot(s) may not fully cut off the signal. Pots are notorious for not moving the wiper contact all the way to the very end of the resistance element (in either direction). There may be some small resistance left between the signal (on the wiper contact) and ground, giving your pedal some signal to work with.
Hope that helps.
sumgai
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