"Has anyone else got one other than Al and Jeff?"
Yes, there are a bunch of arcade game collectors that have them.
"Has anyone ever tried to built the probe for one?"
Not that I know of. The probes always get separated from the
units (along with the docs and pods). The probes are going for
big bucks on eBay ($75-$100). Popular pods (6502,6809,Z80,68K)
sell pretty high there as well. Of course, what this stuff
sells for on eBay is LOW compared to what the used test equipment
scalpers want for them ($250 and up for pods).
9010s are very useful when you're trying to debug embedded hardware
(like video game boards) that have no I/O
"Has anyone ever tried to repair the tape drive
capstans on them?"
They are Braemar mini-data cassette drives, you may still be able
to get parts from them, and cassettes (which are NOT the same as
mini dictation cassettes)