I have an old Fender Jazz Bass with a serial number from 1978. It needed a bit of setting up and I googled the ‘micro-neck adjust’ feature mentioned on the neck base plate and couldn’t find any information. So I thought I’d share what I found here so other people can find it more quickly.
The truss rod adjustment requires an 1/8″ allen key, the micro-neck adjustment is 3/32″. It was very stiff but some gentle leverage worked and I found that turning clockwise set the neck backwards and vice versa. By tweaking the neck angle first, then the truss rod and finally the bridge saddles I was able to get a much nicer action and overall playability. (Saddle height requires a small flat screwdriver, intonating requires a larger cross / philips head screwdriver).