I did some fine tuning on my Gibson ES-225T over the weekend. One of the things that has bugged me is the location of the pickup is parallel to the top, but not to the strings. I honestly don't have a lot of experience with archtop Gibbys with P-90 pickups, but I suspect this is a common issue.
Since the pickup is also stuck in the center of the space between the end of the neck and the bridge, the tone is so-so. I'm thinking it might help the tone if we get the pickup more parallel to the strings.
The way a P-90 adjusts is by shims. From the top in this view, you can see the pickup cover, a thicker plastic shim, then the one shim I have at the bottom to raise it up. When I got the pickup from Lollar, I bought a set of fiber P-90 shims, which helped raise it up closer to the strings. But the tilted angle has been bugging me for a while.
How to fix this? Here's what I came up with.
Since we don't want to raise the neck side, we want to create a wedge shape. So I cut the fiber shim with a razor saw just beyond the mounting holes.
I tried using an X-Acto, but boy is that fiber hard to cut. Hence the razor saw.
I put it near the edge thinking that I needed to be get the proper angle of approach to the shim.
It worked perfectly. I only needed to angle the two 'ears' on the shim, so I had good control with the sanding stick.
You can see the wedge angle on the ears. I tried to get the edge just beyond the screw holes as thin as possible. That's the edge that will be on the neck side of the pickup.
The arrow points to the new wedge shim in place on the guitar.
It seems to have made a difference in the tone of the pickup - seems to have more punch. And it looks much better to boot.