How can I fix a bobbin problem with a Singer model 6412?

I received a Singer 6412 without an instruction manual, so am operating without a net (except for over 40 years of sewing experience!). The machine appears to be pretty simple to operate, but I discovered that the needle consistently hits part of the bobbin assembly. Changing the needle did not help, and I'm having a "dumb" day and can't think about what else to try. Anyone have a suggestion? Thanks.