Well, son is married, visiting family have gone home and life is back to a semblance of normal, so I finally got back to this project. As it turns out, whoever worked on it before had the diffuser in backwards:
Backward diffuser.jpg
You can see it is flipped left to right, with the white mask for the markings around the volume control on the right in this picture, which is the left from the front (volume control is on the right on frontal view)
Here is the way the diffuser was oriented against the bulbs. The poorly drawn red circles show where bulbs and holes for the bulbs do not line up:
Diffuser as it was.jpg
And flipping the diffuser over makes the bulbs and holes line up:
Diffuser as it should be.jpg
I couldn't include the last pic in this post so will show the final result in the next. I see I still haven't got the hang of placing full size images in the text of a post.