Here is a gathering of valuable information to help you understand using and calibrating your B&K tube tester. I will guide you to various links here, and you'll find large scans from my personal B&K tube tester manuals. Keep a few things in mind as we journey through all of this.
B&K 500 Manual. This is the meat and potatoes of the B&K 500 manual. The theory is given on why the 'Gas' test is a very useful tool for the TV service technician. File sizes range from approximately 139K to 268K, with various download times.
B&K 550 Calibration Instructions. These calibrating instructions are pretty well used verbatim for all the relative models, so I may just put this one 'set' up. The file is approximately 154K in size. (Approximate download time: 50 seconds)
B&K 707 Calibration Instructions. These instructions differ from the Model 550 only in that the appropriate sockets are not identical. Otherwise, the target values for such parameters as AC signal and DC bias are exactly the same. The whole page will load very quickly in part because the 33K file size is pretty efficient. (Approximate download time: 10 seconds)
B&K 707 Schematic. It seems other 'freebie' downloads of the B&K 707 manual are of a poor quality; especially the schematic. In an effort to help ease your frustration (or perhaps only offer it in a different form), here is a very high resolution scan of the schematic. Be forewarned; it is a 268K file size. But even Mr. Magoo can read this! (Approximate download time: 88 seconds)