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Removing the Quartz Lock on your 1200 By Ralph Encarnation
First let me tell you what the mod does. Turn on your turntable and press on the side of the platter like if you are trying to slow it down. Notice that when you press down harder the platter is jerking. You can tell by looking at the red strobe. The lights should be jerking as you press harder on the platter. Also the platter does not want to slow down smoothly when you press down on it. So most dj's keep the beats in sync by adjusting the pitch control slightly up and down.
With the mod you can keep the beats in sync by applying pressure to the platter and adjusting the pitch control after the mix.
When you do the mod it will stop the jerking motion. As you press on the platter, the platter slows down gradually without jerking. I find that it is easier to mix this way because you don't have to fiddle with the pitch control while you mix. Just apply a little pressure to the platter to keep the beats in sync. Let off the pressure and the platter speeds up. It basically turns the mkII's into behaving like the old SL-1100's which where the worlds easiest turntables to mix with in my opinion. If you scratch, you will probably will not like this mod so don't try it. Try this mod at your own risk. Don't come crying to me if you screw up your turntable. It is a very easy mod to do and it is also easy to unmodify it if you don't like the mod. The mod is not for everybody. If you are happy and comfortable with your style of mixing then don't bother with the mod. The mod is only called the quartz lock mod because that is the name that somebody gave it a long time ago and the name stuck. The quartz lock is still in the circuit just like a regular mkII. All the mod does it stop the platter from jerking when you apply pressure to it. It will slow down smoothly when you apply pressure. Your pitch control still works the same and all the torque is still there.
Look on the circuit board for PT17 and cut one side of it and lift up on it a little bit so it doesn't hit the part that you snipped. Don't cut both sides of it because you will probably loose it if you do, just one side of it is all you need to cut.
That is all there is to it, but you may not be done yet.
Don't put the black cover back on yet, but go ahead and put the platter back on. After you have the platter back on, put the pitch control on zero and turn the turntable on. If the strobes are going faster or slower when the pitch is at zero, you will have to adjust the variable pitch resistor underneath the platter. Turn off the turntable and remove the platter again. Look for a blue variable resistor marked "pitch". There are two, one is marked "brake" and the other is marked "pitch". Turn the one marked "pitch" a tiny bit and put the platter back on and try it again. You will have to keep doing this until you get the pitch set at zero. Then put the black cover back on when you are done.