Go to Ebay and type in this number under the Ebay Search
280177488657 It will be for a B&K 747 calibration service.
They may have manuals, etc. I know they can perform the service. The calibration may not be hard but if your unit requires tubes you have to have the calibration tube in it. If it is solid state it may be much easier and maybe not require anything but the turn of a few buttons. Do a google search for the model you have along with the word manual and you should get some hits. Ctech may be able to help too.
Alltubes.com is a nice site too. I've been there before as well. You may be able to get a manual from them there.
Good Luck
