As was mentioned previously, most B&K tube testers calibrate with the same procedure, so this one page can be applied to B&K tube testers other than the 550. I will give you a tip right here; when adjusting the DC bias level, be forewarned that without pressing the 'Test 1' button, there will be about -80VDC or -90VDC present! This keeps the tube biased at cutoff when testing for 'shorts' or 'gas', and actually testing the tube for gain will lower the bias to approximately -2.5VDC. So please take due caution with any meter you use. A final tip; to make the 'Shorts' test a little more sensitive, I use a 2.2Meg resistor. Other than that, everything is pretty straight forward, so here is how you calibrate the typical B&K tube tester.