Reference: Installation, Operation and servicing Instructions Model 350C Cryodyne Cryocooler, page 36

• Cool down the cold head and leave it cold for at least three hours.
• Shut down the compressor
• Immediately disconnect the helium return and supply lines from the cold head. Protect the line connectors with a protecting plug.
• Prepare the service manifold by connecting two helium lines to it.
• Be sure that the yellow valve at the manifold is closed. Connect the other ends of the lines to the cold head return and supply (position is not relevant).
  Note: Before connecting, check that the connectors are clean and rubber gaskets are in. Reduce the pressure in the cold head to a level of 50 psi (3.3 bar) by opening the yellow valve.
• Note: never go below this value, to avoid introducing additional contamination.
• Warm up the cold head for approximately 4 hours. Second stage of the cold head should reach room temperature.
• Connect the manifold to the high purity helium bottle, through a pressure regulator. The regulator should handle more than 300 psi (20 bar)
  Note: flush the regulator and copper pipe with helium before connecting it to the manifold.
• Be sure that the cold head motor cable is connected to the cold head connector (cable attached to the helium lines)
• Perform the following sequence:

1. Backfill the cold head with helium to a static charge pressure of 250 psi (16.5 bar)
2. Depressurize the cold head to 50 psi (open yellow valve in manifold slowly)
3. Perform flushing steps a and b four more times
4. Pressurize the cold head to a pressure of 250 psi and run the cold head drive motor for 20 – 30 seconds, by means of the compressor "ON-OFF" switch (cold head "ON-OFF" switch must be ON)
5. Perform step a to d four more times.

• Ensure that the cold head is pressurized to a pressure of 250 psi
• Disconnect the service helium lines from the cold head and reconnect the return and supply lines.
  Note: Before connecting, check that the connectors are clean and rubber gaskets are in. In case that the gasket is dry, lubricate it with "N" type grease.
• Run the compressor for 30 seconds and switch it off. Check that the static pressure is within accepted range (see compressor meter)
• Start the compressor and pump out vacuum vessel of cryostat.
• After 24 hours, briefly stop the compressor and verify the static pressure again. If pressure is below compressor rated value, a helium refilling must be done.