Another thing is spring tension . You are dealing with four springs. Players bend springs to keep pads from sticking. If someone has tampered with the springs you will not be able to adjust these keys.
I think what happens here is a sax is not playing right for some reason and the player sees these two screws right on top of the horn ...and then you get..."Maby if I tighten these two screws...."
If the horn isn't working anyway, how much worse would fiddling with the adjusters make it?.
There are many reasons why these screws can go out - and not all of them are 'doom and gloom'. Pads settle, buffers settle, screws come loose - and they might not even have been set right in the first place.
That means you have to jump in your car, take an hour's round-trip drive to see a repairer who will probably spend two minutes tweaking a screw and then not charge you. It's cost you and it's cost the repairer.
Steve I agree that anyone can adjust the lever for G# and Bb but I dis-agree they can do it without using a leak light, Like ken I find lots of instruments needing repair becuase they customer has done there own adjustments via your description here. The problem I always find is that there are micro leaks and geometry issues with the keys that can only be found using a leak light, simply playing and adjsuting was exasperating there problem, becuase suddenly F was leaking and they were still adjusting for G#.
I swear that if anyone wants to do a repair on there sax the first tool they need is a leak light, not having one is plain stupidity, its like saying I want to change the tire on my car but Im not going to buy a car jack.
Blimey! There must have been some right shonky repair work around before the leak light arrived.
The leak light is a diagnostic tool, an aid. You still have to know how and when to use it, and that in itself is a skill.
If, as a novice tweaker, you jump straight from picking up a screwdriver to shoving a leak light down a horn, you're going to miss out on learning the basic and fundamental skills. Sure, a light lets you see what's happening - but a cigarette paper lets you feel what's happening.
When someone starts doing their own tweaks what they most need is an understanding of how the mechanism works - what does what, and why. Once that's in place, sure, a leak light can save time. But necessary? Oh please.
It's one reason why it's so hard to find repairers who know how to handle a Grafton...
And lastly - when I first picked up my tools over 30 years ago now I used to find that the majority of horns that came in had little toolkits stashed in their cases. A screwdriver, a blade, some cork and glue, even a few springs. They almost always belonged to the older players, who thought nothing about doing their own minor tweaks. As the years went by I saw fewer and fewer such players - the toolkits were replaced with tuners, fancy ligatures and gadgets.
It's not that the skills have been lost, it's more to do with the 'Oh God, don't do that' mentality that seems to prevail these days.
I'm sure there are any number of players who might not even know which end of a screwdriver goes where, but I reckon that most people - given the right information and some encouragement - can handle these very basic tweaks.
Like Ken said from the off "You have to know what you're doing and why you're doing it". So tell them - and remember...if someone get an adjustment wrong, it's not the end of life as we know it. It's just a horn.
Regards,