Hi. Many Philips Turntables have this system of setting VTF. An example is Philips GA 312. If u read the owners manual of GA 312(available on internet) or 242(I have the original owners manual), the procedure is laid down: that is set the front sliding weight to zero , then balance tonearm using counterweight, finally slide the sliding weight forward to set VTF. Now, interestingly, the 312 has a separate knob for anti-skate caliberation, whereas in 242 it is fixed!
Many Tts e.g. Dual 1009 etc have a slightly different system, in that, after balancing the tonearm you set the VTF using a knob which exerts downforce with the help of a spring. Here sliding weight is eliminated.
On another note, I recall that there is or are some tt's which use the sliding weight to tune specific cartridges resonant frequency. Maybe some of our more knowledgeable members may enlighten.
