Kurt,

As you probably expect the programmer and the eraser are both conspiring against you.

The eraser set's the level of your "1"'s and the programmer sets the level of your "0"'s.

Since a "fresh" '520 works it sound like you are not getting complete eraser but are getting an erasure ( a "1"'s level) acceptable to your prom blower.

I have used the '520 quite a bit and program them with a S4 blower. I have never had a problem erasing them (providing you remove the opaque label) if your eraser is fairly old sit the part right under the lamp.

regards,
p