Where can i find free repair or service manual for tough book cf-51

There is a website that offers "free" service manuals for
several brands of laptops including for certain models
of Panasonic Toughbooks:

http://www.tim.id.au/blog/tims-laptop-service-manuals/

I cannot guarantee you will find your model listed but
I can say that I have used this site and the service
manuals are authentic.

Good Luck!
Regards,
Richard - Montreal Based
Panasonic Canada Toughbook Authorized Dealer since 1989

Go to www.panasonic.com and then support, then look for manual download. type in the model, then it should give you the manual. if for some reason they do not have it, then just google the model number with manual after the model and you should be able to find it there. hope this helps.. Ron