Hi,
I've recently got a gibson sg.
It seems that the pick ups have been lowered, does anyone know why this would have been done, what effect it is likely to have and how I might return them to their origional position?
Well, with the pickups lower you are going to get a quieter volume and softer sound. There should be a single screw on each side of the pickup...those raise and lower it. Play with adjusting them a bit until you find a sweet spot you like...you aren't going to hurt anything. If they happened to lower them too far and the screw came out of the pickup's mounting plates, you will have to take either the pickguard (full pickguard SGs) or the pickup rings (half guard SGs) to put them back together...the screw goes through the guard or ring, then the spring goes on the screw, then the screw tightens into the mounting plates on the bottom of the pickup.
I've heard that adjusting your pickups too close to your strings can cause problems, something something magnets something something. Someone will be able to explain it better than I.
Gibson designed these humbucking pickups so that each of us could adjust the height of them according to the sound we prefer. The best way to decided what you want is to play it a lot and listen. If they are too close to the strings, the magnets can damp the vibration of the strings themselves, and this muddies the sound. If they are too far away, the intensity of the signal drops a bit, but the sound is clear and you can turn it up. As was said above, you can't do any harm by changing it.
play it the way it is first... someone might have set it that way for a reason. you are not obliged to keep it that way, it's your guitar now. but listen to it and think about whether it sounds like you expect. or better... or worse. Some Gibson pickups sound great when they are lowered into the body of the guitar.
a good working distance to begin with is 5mm (distance between the polepiece and the string). buy yourself a small steel ruler from the hardware store, one that measures mm and small fractions of an inch. keep it in your guitar case, you'll use it. also buy yourself a few HIGH quality screw drivers... #0 and #1 Phillips, and a small Flathead screwdriver, one that fits the polepieces on your p'ups and the intonation screws on the bridge.
I like to adjust the height of the polepieces to match the radius of the bridge. You can do his by eye, or buy yourself a radius gage if you want to be exact. but exactness is not necessary, and I will also adjust a polepiece up or down if one string seems to jump out more than others.
Play it, listen to it, tweak it, play it some more, and let us know how it works for you.
And give your ears a chance to adapt to what they are listening for. With practice, you will be able to tell the difference with only a 1/4 to 1/2 turn of the screw.