@ the OP, if you are testing drivers ok, for testing output power tubes not really worth the money
Tube testers are old instruments, with degraded parts, right now Roger is trying to rebuild the transformer of a 752 A I sent him some time ago, Roger he is one of the best if not the best, very honest and straight person. With the tester calibrated and ready to go it is advisable to use a variac to supply plate current to the tube so the measurement is more accurate if your tester is old like most are.
Don expect you will be able to measure tubes with high precision, unless you spend a lot of money and time. I own a BK707 too and it is a toy it constantly drifts.
Not trying to discourage you but it all depends on what you want it for. Which tubes and amp / preamp will you be using? How often will you be measuring?
Tube testers are old instruments, with degraded parts, right now Roger is trying to rebuild the transformer of a 752 A I sent him some time ago, Roger he is one of the best if not the best, very honest and straight person. With the tester calibrated and ready to go it is advisable to use a variac to supply plate current to the tube so the measurement is more accurate if your tester is old like most are.
Don expect you will be able to measure tubes with high precision, unless you spend a lot of money and time. I own a BK707 too and it is a toy it constantly drifts.
Not trying to discourage you but it all depends on what you want it for. Which tubes and amp / preamp will you be using? How often will you be measuring?