Thanks for the concise response. I'm hoping these threads will be helpful to others who might have questions like these but are afraid to ask.
Regarding a set using both types of ion traps. My RCA 730tv1 has both types of trap on it. When I was writing about it's restoration there were a lot of people who said that doesn't make sense, but it definitely needed both traps for the best picture. Remembering my experience with that set I thought I would try adding a pm trap to my 630. The difference is night and day. I just can't get enough brightness out of the 10BP4 with the electromagnet alone.
Here is a picture with only the electromagnet trap. This was the brightest I could get after much adjustment.
Here is a picture with both traps. The brightness control was not changed between these two pictures. The ambient light was also not changed even though it looks like it was. The only thing I adjusted was horizontal and vertical centering as the pm trap pulled the beam at a different angle.
What would account for the original trap not being able to get maximum brightness out of the 10BP4?