It's altogether too easy to short a supply to ground when doing the sorts of operations you've been doing. You may want to do a quick ohmmeter check to see if that happened somewhere along the way. Check +5 to ground; +12 to ground; and +5 to +12. I don't know if the SE/30 has -12V, but if so, check continuity between it and the others.

To avoid forward-biasing junctions that can confound the measurements, I recommend using the ohmmeter in "ordinary" mode (i.e., not "diode-check" mode).