Ok, here we go!
To solve the double 0% problem, you'll need to open up the base of your table for this. First secure all loose parts from your TT (lock the arm, remove the 45RPM adaptor and the headshell).
Put the dustcover on (or top of the flightcase, anything that allows you to put the TT upside down without breaking the arm).
It's best you put it upside down on a large pillow when you use the dustcover (for more stability because the pillow "absorbs" the little extrusion from the dustcover).
Once upside down, it's screwdriver time. First unscrew the four feet by hand. After that look at the black rubber base of the Technics. You should see 21 (not more) screws ordered in two circles.
You'll have to unscrew them all. The only screws you shouldn't touch are those that hold the cable cache.
Once you unscrewed it all, remove the black rubber base (it can take some wiggling and pulling before it comes off).
Watch out not to rip the cables off.
You should see the bottom side of the circuit board now. Look where the pitch slider is (well the circuit board of it). There you should see a little hole (it gives access to a potentiometer, called VR302), it may be easier if you unscrew the pitch slider, to improve accesibility.
Now the question is, do you have a multimeter??? If yes, it's easier. Measure the impedance/resistance of the little potentiometer (center pin - and, most outer pin +).
Factory default is 2.7 kOhm, but I've had several SL's where 3.25 kOhm gave a better result (I've fixed sh*tloads of SL's, trust me). Point is, no two Technics are the same, so experimenting is the key.
If you don't have a multimeter, no problem, just adjust it (be careful it's VERY precise, a slight turn is already a huge change in resistance).
Multimeter or not, it's always better to try the setting and correct if necessary. Just temporarlily put the remaining part of the TT (no need to replace the black botton each time) normally on the pillow, and try the pitch slider.
Just do it like this. Start at 0% and move to negative pitch. Watch very carefully. The dots should progressively start moving backwards (if they move forward at first, even slightly, you need to adjust more). Then do the same the other side (positive = dots should begin moving forward directly, not backwards at first...). Adjust again if necessary.
Ok if your SL wanted to cooperate (some are totally broken in that matter, but that's very very rare), you should only have one 0% left.
Now wait. If you want, we'll calibrate the pitch range so it is as factory default as possible(+/-8%). For this we'll access from above. Remove the platter, then the black plastic cache (4 or 5 screws holding it).
You should see the TOP of the circuit board, and somewhere on it a blue potentiometer (VR301) with PITCH written next to it. This is to adjust your pitch RANGE. Normally to be very precise, you'll use a frequency counter and set it to 262.08 kHz, but here it's better to do it by hand, always testing.
The best way to calibrate is to set your pitch at +6%. Adjust until the +6% strobe dots stand still (the little ones, of course you need to put your platter back while testing).
Once done that, set your pitch at approximatively 3.3% and the respective dots should (almost) stand still too. Same for -3.3%. From experience, I can tell that if you have an SL that has perfect pitch (respective dots from -3.3% AND +3.3% AND +6% stand still at their respective speeds), you may consider yourself very very lucky. That's why most of the time, we calibrate at +6%, it gives best results and ensures you you have about +/-8% pitch range.
PS : there's also another pot (older SL's : metal, newer : blue) VR201, with BRAKE written next to it. This is for adjusting the brake. Adjust it like you want (normally when set right, the platter should could to a FULL stop (this means full, not even going backwards again) in a angle from 90-120°.
Try in different conditions (record and stylus on the platter, stylus in the beginning of the record, end, 33RPM, 45RPM, different pitch settings, ...), if it stops dead 9 times out of 10, it's pretty well calibrated 
Once you are happy, just put everything back as it was (plastic cache, platter, pitch slider if you removed it, rubber base and all its screws, the four feet).
Voila, if everything went fine, you should have a calibrated Technics now!!!
Hope this helped, if you have more questions, feel free to ask.
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