I think you and me and Clive and Leigh are on the same page about what 'calibration" means. You have no reason to apologize... this is a discussion forum and the discussion is good!
I think where we depart is the D-I-Y aspects. Turning potentiometers and varable resistors and what-not isn't a particularly good idea if you don't know the correect settings or how the measure the correct settings. This is generally true with all sorts of electronics. I applaud the D-I-Yers (of which I am one) but always remain aware that there are some who simply don't have the skills, knowledge, and tools. That may not be the case, I don't know... but what I do know is that blindly turning adjustments often does not result in successful conclusion.
Please understand, i'm not being critical of you... just discussing the flip side. Thanks for your participation on this forum!