(PDP-8) RK05 problems. Anyone have the source to RKUTIL?

My RK05's are acting up again. They first acted like this when I was bringing them up after a 30 year nap. The symptom then was that one of the Maindecs for disk testing would complain that it couldn't write because a CE disk was in the drive! (Which brings up the quesiton: Why would it think that? Is there a wire on the disk interface bus that is pulled down when a either a CE disk (how??) or else the disk alignment suitcase is plugged in?) Anyway, now that I can run RKUTIL I have a new problem that just happened this weekend. I can no longer select option 4 (read/write test). It simply reprints the prompt, no error message at all! I assume this is the CE present problem rearing it's ugly head again. RKTUTIL worked fine up until this weekend. Anyway, I'd like to look at the RKUTIL source but can't find it anywhere. Does anyone have a pointer to this? Also, if anyone knows what triggers the CE present condition I'd like to know about that too. Thanks, Marc