Despite the age, a great Calibration manual for yer' techies.
http://www.massive.com/in_tune/technics_pitch.html

Lost your service manual? Get it here: http://www.aboutdj.nl/downloads/technics_sl1200_service_manual.pdf

Can be found here: http://www.technonet.dk/turbulent/article_1210+16.html

Unfortunatly in Danish, but because of it's quality I'll post it anyways.

Basic improvement hacks can be found here: http://www.mio.co.za/article.php?cat=&id=238