There seems to be a bit of confusion regarding the SLW Block Adjustment. Scott Losmandy does have a very helpful video??that illustrates the process but I realize people have different ways of learning and so I wanted to offer another perspective on it. I am very open to others chiming in with their own techniques and considerations.
I've attached some photos that I have labeled with the terms I use for each of the parts. I'm happy to adjust these if there are actual names for these various screws, but these labels work for my understanding.
The worm gear sits between two moveable blocks. One of these pivots and one of them slides in a short groove so that it may travel towards and away from the ring gear. I call these the "Pivot Block" and the "Travel Block".
The two adjustment screws that sit in cradles on the very bottom of the SLW hold the blocks to the base of the mechanism. These cradles have the purpose keeping the screws square to the pivot/track openings. These screws should not be tight as they must allow the pivot block to pivot and the track block to track easily, but they should be screwed just to the point of first gentle contact and then backed off a whisper. I call these the Pivot Block Tension Screw and the Travel Block Tension Screw.
The rest of the screws are in what I call the Worm Block Cover. Two are recessed and two stick out. The two recessed screws in the cover hold the Pivot Block and the Travel Block firmly against the cover. Ideally, the Pivot Block and the Travel Block are snug against each side of the worm gear so that the worm gear cannot slide back and forth. The Pivot Block Lock screw should be loosened just a tad, so that the Worm Block cover has a little bit of space (like 1mm) to the left of it, then that Pivot Block Lock screw should be tightened down good and tight. This secures one side of the space that the Worm Gear occupies. Then you can loosen the Travel Block Lock screw slightly and you will see that the Travel block has a little bit of play built into it. If you remove the Travel Block Lock screw completely from the Worm Block Cover you will see there is a small eccentric slot that the Travel Block Lock screw seats into so as to allow for this next adjustment. I press the Worm Block Cover towards the ring gear and rotate the axis of the mount (RA or DEC as appropriate) with my other hand so that the Travel Block gets pressed towards the Pivot Block. Then with my free thumb I maintain this pressure on the Travel Block towards the Pivot Block while I use an allen wrench to tighten the Travel Block Lock screw nice and tight. The ultimate gain is to get rid of any extra space on either side of the Worm Gear so that it can only spin on its axis and not slide side to side in the bearing race. Once this is complete there should be pretty much no play when you try to rotate the axis back and forth by hand.
Finally now we are at the Spring Tension Screw and the Backoff Set Screw. These two screws operate in concert to fine tune the amount/limits of pressure that the spring will exert to press the Worm Gear into the Ring Gear. Start by turning the Backoff Set Screw counterclockwise until it is no longer making contact with the underlying plate. There are a few different approaches to these two screws but the technique that Scott uses in the video is to tighten the Spring Tension Screw all the way down, then back it off between 1/2 and 3/4 of a turn. I have found that backing off the screw one and a half turns works just as well and makes me less likely to accidentally over-tighten the Spring Tension Screw. At this point Scott has the transfer gear cover removed and he gently tries to turn the upper transfer gear while he slowly screws in the Backoff Set Screw clockwise. You will feel the Backoff Set Screw make contact with the plate underneath and as you continue to slowly turn it clockwise. Somewhere shortly after it makes contact with the plate you will feel the tension in the upper transfer gear release and it will suddenly turn freely. There is a veeeery small transition point in that Backoff Set Screw. Too little and the upper transfer gear is impossible to move... too much and it feels too sloppy. Over time you'll get a feel for it but you don't want that gear to feel tight. You will likely get a motor stall and you will stress the gearbox more than you need to.
Once you get that set, use the Hand Controller to slew the adjusted axis all the way around each way to make sure that you don't get any binding or stalls anywhere in the range of movement... no stalls? no binding? you are good to go.
Personally, I find that when I only back off the Spring Tension Screw 1/2 a turn, the Backoff Set Screw adjustment is super finicky. When I back the Spring Tension Screw one to 1.5 turns, it is a little more easy to feel. But if the Backoff Set Screw is not making contact with the plate underneath yet and the upper Transfer Gear is already easy to turn then I don't have the Spring Tension Screw tightened down quite enough.
Clear as mud?
Ryan Noonan