It is just amazing that there are such radical differences differences between two arms out of the same 'kitchen' and each bearing the TPA12 nomenclature. I wonder which arm came first - yours with the adjuster along the side, or mine with a thumbwheel on top.
You also have me slightly worried but I have no time now to check things out. This is the little niggle: I was perfectly able to adjust the VTF up or down with the thumbwheel on my arm. I doublechecked the VTF by using my electronic scale and I'm tracking @ 4.5g.
I just find it incredible that there's such a radical difference between these two TPA12's.
From working on mine, I had to take it apart completely as the mazak part of the arm needed a lot of sanding and polishing to get that chrome look.
When putting it together again, I re-packed the bearings with grease and as far as I remember, there are threaded cone-shaped pivots on each side. So, you can try and centre the arm between the pivots and use each screw for fine adjustment. I cannot recall seeing a spring on the side but after Iain's discovery, I think I should take another look.
Nice vintage avatar too, I notice