Hello. My name is Michael. I can help you with your question today.
I am both, but of the two, a fitness equipment tech would be more accurate.
Actually what you did with the screwdriver was the correct adjustment to tension the cable properly. It's not something I would have imagine someone would do based on intuition, but somehow you did - and you did it about as close to correctly as you can. Impressive.
Maybe you are have a latent fitness equipment tech in you as well?
Do you have anything left to do about which you have questions you haven't answered yet?
How far can you adjust it when only manually adjusting it?
When it is tightened that much, though - is that when you only have 7-11 available?
IF it goes up to 90-20, then that could be the case.
Adjust the tensioner by turning the cam in the opposite direction.