Please remember that service manuals are written before the product goes in to production. Certain manufacturers will update and revise them as the product changes and issues are found and revised. Some are great at this. Mitsubishi is not one of them. The LT-30 SM is pretty bad and basic, as is the LT-20. At one time, that adjustment may have been the intended method and I have only worked 3 units (own 2) plus LT-20’s & 22, & LT-5. Maybe some one else will chime in with a better picture, of the screw & bracket, but on my units I did specifically look at that adjustment based on the same SM instruction in case it needed adjustment and all I’ve seen were still factory lock painted in place, so no adjustment required. If the sticker still covers the hole on yours (one of mine was half peeled off), then it is almost certainly correct. Also, the screw IS accessible (only) from the outside, under the sticker, but if your unit has a base colored sticker over it, I assure you it does not actually adjust anything except tighten the bracket down.
BTW, you do realize that the “on-off adjustment” does NOT refer to the horizontal movement itself on and off, but when the horizontal tracking as a whole is activated on or off. Tracking does not occur when the TA is cued up (OFF) or in the rest position. That adjustment switches it in when the TA is down in play only (ON). I realize I did not make that clear, earlier so it may have been confusing.
Both tracking bulbs on at the same time without the center “good” light, was addressed in a previous post somewhere, I recall reading it. I thought it meant both bulbs burnt out, but I remember it was resolved.
TA disassembly to that level is a royal PITA. It is not fun. Maybe for some but I found it annoyingly frustrating. You have to desolder the delicate cartridge wires from the mute switch, to get enough slack to pull the arm out. We all have/had pictures to make sure we get it back together because the SM is useless in that regard. Soldering fine TA wires is right up there with getting teeth pulled just about.
To see what the tracking screw does, requires total TA disassembly to the level shown In Aerobats photo. It just pushes by rotating the spring loaded (which is seen in the photo) bulb holder part relative to the brass post. The shutter is fixed such that neither bulb is revealed to the sensors in the exact center position.
