[Phlogiston]

Would strongly that you get the procedure and do it yourself. You will gain a much better understanding of what your tester is doing and how it is being done AND possibly what to look for in respect to tubes that tube testers do not test very well. Schematic for 800A here:

http://bama.edebris.com/manuals/hickok/800a/

But you will need to search for alignment instructions as well.

MOST important to note that the alignment(s) were written for people using 10,000 ohms/volt meters ( you will need to use resistors if using a digital VOM).