My 720A developed a small leak at the resistor can oil seal. The seal does not seem to be in the manual, so I contacted Fluke. They seemed a bit baffled about what it could be. I sent them a couple of photos and they finally came up with:
171959 EA 23.70
Item Desc :SEAL,BUNA,3/8 EXT THREAD,COMPOSITE,STEEL RETAINER,CADMIUM PL,.750 OD,.063 THK
So, only 24 bucks for a 50 cent bolt and 10 cent O-ring.
I don't think enough oil leaked to make a difference, but I also asked them about what oil to use and they responded that they don't sell the oil, but to use "Grade 5 mineral oil"... I assume that is viscosity 5. Does anybody know of a suitable oil available in small quantities? I'd prefer not to go dumping in some no-name goop of unknown quality/purity/virginity from the local hardware/grocery/etc store.