Hi Stefan,
Welcome to "The Lab"..!
If it's related to the 179-120 / 179-140, then check:
http://www.gyraf.dk/schematics/NTP_179-140_Manual.pdf
Otherwise you may be in trouble - NTP schematics are very rare, and the company went under for the third time last year.
If you find it, make sure to post a copy here!
Jakob E.