Step 1 -	Measure the tube minimum anode voltage.
Step 2 -	Tube soaks in 100°C for 20 sec., and soaks in -190°C Liquid Nitrogen for 20 sec. Repeat the procedures for 20 cycles.
Step 3 -	Measure the minimum anode voltage again and for appearance inspection.

1. Tube is not broken, or damaged.
2. Minimum anode voltage: Increase must be < 10% of initial value.