There were visible amounts of black “grime” on the upper end of the displacers and piston; the Vanderbilt Macromizer cold head was dirtier than the J-H unit.6.Cleaned the 1ststage region of the sleeve interior by hand with Kimwipes and isopropanol. A considerable amount of black residue was removed, which Steve said is probably oil from the flex line connections or from the cold head motor.7.Cleaned the 2ndstage sleeve interior with Kimwipes and isopropanol but using a copper rod bound with rubber bands at the end to “plunge” the confined space.8.Unpacked the new cold head and brought it in. The head was bolted to its own sleeve, which was pressurized.9.Prepared a standard tank of He with a regulator, valve and line for pressurization of the new cold head.10. Reattached gauged valve vent to new head He return port.11. Attached He cylinder line to new head He supply port.12. Connected compressor power line to new head socket (power on), opened vent valve to depressurize completely. Disconnected power.13. Removed 4 hex bolts and extracted head from sleeve. Quickly installed head in existing sleeve on instrument. *Did not replace o-ring on J-H instrument, didreplace o-ring on Vanderbilt instrument.