Calibrating Pitch Faders on Technics 1200mk2's

[TrueWind]

Hello DJF'ers,

I have a pair of decks that have faders that are not calibrated. After googling around and reading the technics service manual I decided that I knew (or so I thought) had to calibrate the faders.

Well, I did the following to both faders:

1) Set the Fader's Resistance to exactly 2.7K
2) After doing so I started turning the blue knob by the motor to adjust the percentage for the pitch. Using Traktor and Serato BPM readings (with a 100BPM track loaded) I discovered the following: The Blue Knob WILL Adjust the pitch range on the Plus Side of the Pitch, however the minus pitch percentage gives the following: (91.70 BPM at -8% on the slider / so a -8.30%) when the blue knob is turned all the way to the left (giving only a +3%).

When the blue knob is all the way to the right, (I get 91.95BPM at -8% on the slider / so -8.05%) but I get a 112.65BPM @ +8% so a +12.65%

So I finally turned the blue knob so that the arrow is about going diagonally in this direction "/" the big arrow points towards the space between the "C" and "H" where it says pitch. With this, I get a Good accurate pitch from 0 - +6 percent (meaning that +1% on the pitch = +1 BPM.. etc). Then I get to +6.7% or +6.8% with the slider, and Traktor Reads 107 BPM. Then when I go all the way to +8%, I get 108.76 BPM.

HOWEVER, when I set the slider in the - percentage area, I get the following:
-1% = 99BPM
-1.8% (approx) = 98 BPM
-2.3% (approx) = 97 BPM
-3.2% '' = 96 BPM
-3.93% " = 95 BPM
-4.5% " = 94 BPM
-5.7% " = 93 BPM
-7.15% = 92 BPM
-8% = 91.86 BPM

How DO I FIX This?!

I thought that perhaps it was the pitch slider that was old, but I switched the fader from the other turntable whose fader is much Newer (seems kina as if bought brand new) and I had the SAME Problem....

What am I missing? What did I not do properly?

I know that it is possible to mod the techs so that you either get 3% / 10% / or even 12% pitch ranges... I did get those ranges, but only on one side (the plus side)! I want the standard 8%, but how do I make the percentages increment equally on both sides?!